From patchwork Sun Apr 19 14:10:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497475 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 722D681 for ; Sun, 19 Apr 2020 14:11:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5B13C2223D for ; Sun, 19 Apr 2020 14:11:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726022AbgDSOLm (ORCPT ); Sun, 19 Apr 2020 10:11:42 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45414 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725905AbgDSOLm (ORCPT ); Sun, 19 Apr 2020 10:11:42 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id BFC74209FB; Sun, 19 Apr 2020 14:11:39 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 1/7] proc: rename struct proc_fs_info to proc_fs_opts Date: Sun, 19 Apr 2020 16:10:51 +0200 Message-Id: <20200419141057.621356-2-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:40 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- fs/proc_namespace.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c index 273ee82d8aa9..9a8b624bc3db 100644 --- a/fs/proc_namespace.c +++ b/fs/proc_namespace.c @@ -37,23 +37,23 @@ static __poll_t mounts_poll(struct file *file, poll_table *wait) return res; } -struct proc_fs_info { +struct proc_fs_opts { int flag; const char *str; }; static int show_sb_opts(struct seq_file *m, struct super_block *sb) { - static const struct proc_fs_info fs_info[] = { + static const struct proc_fs_opts fs_opts[] = { { SB_SYNCHRONOUS, ",sync" }, { SB_DIRSYNC, ",dirsync" }, { SB_MANDLOCK, ",mand" }, { SB_LAZYTIME, ",lazytime" }, { 0, NULL } }; - const struct proc_fs_info *fs_infop; + const struct proc_fs_opts *fs_infop; - for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { + for (fs_infop = fs_opts; fs_infop->flag; fs_infop++) { if (sb->s_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } @@ -63,7 +63,7 @@ static int show_sb_opts(struct seq_file *m, struct super_block *sb) static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) { - static const struct proc_fs_info mnt_info[] = { + static const struct proc_fs_opts mnt_opts[] = { { MNT_NOSUID, ",nosuid" }, { MNT_NODEV, ",nodev" }, { MNT_NOEXEC, ",noexec" }, @@ -72,9 +72,9 @@ static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) { MNT_RELATIME, ",relatime" }, { 0, NULL } }; - const struct proc_fs_info *fs_infop; + const struct proc_fs_opts *fs_infop; - for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { + for (fs_infop = mnt_opts; fs_infop->flag; fs_infop++) { if (mnt->mnt_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } From patchwork Sun Apr 19 14:10:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497503 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A818D14DD for ; Sun, 19 Apr 2020 14:12:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8877F21974 for ; Sun, 19 Apr 2020 14:12:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725905AbgDSOML (ORCPT ); Sun, 19 Apr 2020 10:12:11 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45458 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725949AbgDSOLp (ORCPT ); Sun, 19 Apr 2020 10:11:45 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id 9137E209FC; Sun, 19 Apr 2020 14:11:40 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 2/7] proc: allow to mount many instances of proc in one pid namespace Date: Sun, 19 Apr 2020 16:10:52 +0200 Message-Id: <20200419141057.621356-3-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:41 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: This patch allows to have multiple procfs instances inside the same pid namespace. The aim here is lightweight sandboxes, and to allow that we have to modernize procfs internals. 1) The main aim of this work is to have on embedded systems one supervisor for apps. Right now we have some lightweight sandbox support, however if we create pid namespacess we have to manages all the processes inside too, where our goal is to be able to run a bunch of apps each one inside its own mount namespace without being able to notice each other. We only want to use mount namespaces, and we want procfs to behave more like a real mount point. 2) Linux Security Modules have multiple ptrace paths inside some subsystems, however inside procfs, the implementation does not guarantee that the ptrace() check which triggers the security_ptrace_check() hook will always run. We have the 'hidepid' mount option that can be used to force the ptrace_may_access() check inside has_pid_permissions() to run. The problem is that 'hidepid' is per pid namespace and not attached to the mount point, any remount or modification of 'hidepid' will propagate to all other procfs mounts. This also does not allow to support Yama LSM easily in desktop and user sessions. Yama ptrace scope which restricts ptrace and some other syscalls to be allowed only on inferiors, can be updated to have a per-task context, where the context will be inherited during fork(), clone() and preserved across execve(). If we support multiple private procfs instances, then we may force the ptrace_may_access() on /proc// to always run inside that new procfs instances. This will allow to specifiy on user sessions if we should populate procfs with pids that the user can ptrace or not. By using Yama ptrace scope, some restricted users will only be able to see inferiors inside /proc, they won't even be able to see their other processes. Some software like Chromium, Firefox's crash handler, Wine and others are already using Yama to restrict which processes can be ptracable. With this change this will give the possibility to restrict /proc// but more importantly this will give desktop users a generic and usuable way to specifiy which users should see all processes and which users can not. Side notes: * This covers the lack of seccomp where it is not able to parse arguments, it is easy to install a seccomp filter on direct syscalls that operate on pids, however /proc// is a Linux ABI using filesystem syscalls. With this change LSMs should be able to analyze open/read/write/close... In the new patch set version I removed the 'newinstance' option as suggested by Eric W. Biederman. Selftest has been added to verify new behavior. Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- fs/proc/base.c | 31 +++++++----- fs/proc/inode.c | 11 ++--- fs/proc/root.c | 49 +++++++++---------- fs/proc/self.c | 6 +-- fs/proc/thread_self.c | 6 +-- include/linux/pid_namespace.h | 12 ----- include/linux/proc_fs.h | 22 ++++++++- tools/testing/selftests/proc/.gitignore | 1 + tools/testing/selftests/proc/Makefile | 1 + .../selftests/proc/proc-multiple-procfs.c | 48 ++++++++++++++++++ 10 files changed, 124 insertions(+), 63 deletions(-) create mode 100644 tools/testing/selftests/proc/proc-multiple-procfs.c diff --git a/fs/proc/base.c b/fs/proc/base.c index 6042b646ab27..93b5d05c142c 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -697,13 +697,13 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr) * May current process learn task's sched/cmdline info (for hide_pid_min=1) * or euid/egid (for hide_pid_min=2)? */ -static bool has_pid_permissions(struct pid_namespace *pid, +static bool has_pid_permissions(struct proc_fs_info *fs_info, struct task_struct *task, int hide_pid_min) { - if (pid->hide_pid < hide_pid_min) + if (fs_info->hide_pid < hide_pid_min) return true; - if (in_group_p(pid->pid_gid)) + if (in_group_p(fs_info->pid_gid)) return true; return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); } @@ -711,18 +711,18 @@ static bool has_pid_permissions(struct pid_namespace *pid, static int proc_pid_permission(struct inode *inode, int mask) { - struct pid_namespace *pid = proc_pid_ns(inode); + struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb); struct task_struct *task; bool has_perms; task = get_proc_task(inode); if (!task) return -ESRCH; - has_perms = has_pid_permissions(pid, task, HIDEPID_NO_ACCESS); + has_perms = has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS); put_task_struct(task); if (!has_perms) { - if (pid->hide_pid == HIDEPID_INVISIBLE) { + if (fs_info->hide_pid == HIDEPID_INVISIBLE) { /* * Let's make getdents(), stat(), and open() * consistent with each other. If a process @@ -1897,7 +1897,7 @@ int pid_getattr(const struct path *path, struct kstat *stat, u32 request_mask, unsigned int query_flags) { struct inode *inode = d_inode(path->dentry); - struct pid_namespace *pid = proc_pid_ns(inode); + struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb); struct task_struct *task; generic_fillattr(inode, stat); @@ -1907,7 +1907,7 @@ int pid_getattr(const struct path *path, struct kstat *stat, rcu_read_lock(); task = pid_task(proc_pid(inode), PIDTYPE_PID); if (task) { - if (!has_pid_permissions(pid, task, HIDEPID_INVISIBLE)) { + if (!has_pid_permissions(fs_info, task, HIDEPID_INVISIBLE)) { rcu_read_unlock(); /* * This doesn't prevent learning whether PID exists, @@ -3301,6 +3301,7 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags) { struct task_struct *task; unsigned tgid; + struct proc_fs_info *fs_info; struct pid_namespace *ns; struct dentry *result = ERR_PTR(-ENOENT); @@ -3308,7 +3309,8 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags) if (tgid == ~0U) goto out; - ns = dentry->d_sb->s_fs_info; + fs_info = proc_sb_info(dentry->d_sb); + ns = fs_info->pid_ns; rcu_read_lock(); task = find_task_by_pid_ns(tgid, ns); if (task) @@ -3372,6 +3374,7 @@ static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter ite int proc_pid_readdir(struct file *file, struct dir_context *ctx) { struct tgid_iter iter; + struct proc_fs_info *fs_info = proc_sb_info(file_inode(file)->i_sb); struct pid_namespace *ns = proc_pid_ns(file_inode(file)); loff_t pos = ctx->pos; @@ -3379,13 +3382,13 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx) return 0; if (pos == TGID_OFFSET - 2) { - struct inode *inode = d_inode(ns->proc_self); + struct inode *inode = d_inode(fs_info->proc_self); if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK)) return 0; ctx->pos = pos = pos + 1; } if (pos == TGID_OFFSET - 1) { - struct inode *inode = d_inode(ns->proc_thread_self); + struct inode *inode = d_inode(fs_info->proc_thread_self); if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK)) return 0; ctx->pos = pos = pos + 1; @@ -3399,7 +3402,7 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx) unsigned int len; cond_resched(); - if (!has_pid_permissions(ns, iter.task, HIDEPID_INVISIBLE)) + if (!has_pid_permissions(fs_info, iter.task, HIDEPID_INVISIBLE)) continue; len = snprintf(name, sizeof(name), "%u", iter.tgid); @@ -3599,6 +3602,7 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry struct task_struct *task; struct task_struct *leader = get_proc_task(dir); unsigned tid; + struct proc_fs_info *fs_info; struct pid_namespace *ns; struct dentry *result = ERR_PTR(-ENOENT); @@ -3609,7 +3613,8 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry if (tid == ~0U) goto out; - ns = dentry->d_sb->s_fs_info; + fs_info = proc_sb_info(dentry->d_sb); + ns = fs_info->pid_ns; rcu_read_lock(); task = find_task_by_pid_ns(tid, ns); if (task) diff --git a/fs/proc/inode.c b/fs/proc/inode.c index fb4cace9ea41..9c756531282a 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -167,13 +167,12 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock static int proc_show_options(struct seq_file *seq, struct dentry *root) { - struct super_block *sb = root->d_sb; - struct pid_namespace *pid = sb->s_fs_info; + struct proc_fs_info *fs_info = proc_sb_info(root->d_sb); - if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID)) - seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid)); - if (pid->hide_pid != HIDEPID_OFF) - seq_printf(seq, ",hidepid=%u", pid->hide_pid); + if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID)) + seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid)); + if (fs_info->hide_pid != HIDEPID_OFF) + seq_printf(seq, ",hidepid=%u", fs_info->hide_pid); return 0; } diff --git a/fs/proc/root.c b/fs/proc/root.c index cdbe9293ea55..208989274923 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -77,26 +77,31 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) return 0; } -static void proc_apply_options(struct super_block *s, +static void proc_apply_options(struct proc_fs_info *fs_info, struct fs_context *fc, - struct pid_namespace *pid_ns, struct user_namespace *user_ns) { struct proc_fs_context *ctx = fc->fs_private; if (ctx->mask & (1 << Opt_gid)) - pid_ns->pid_gid = make_kgid(user_ns, ctx->gid); + fs_info->pid_gid = make_kgid(user_ns, ctx->gid); if (ctx->mask & (1 << Opt_hidepid)) - pid_ns->hide_pid = ctx->hidepid; + fs_info->hide_pid = ctx->hidepid; } static int proc_fill_super(struct super_block *s, struct fs_context *fc) { - struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info); + struct proc_fs_context *ctx = fc->fs_private; struct inode *root_inode; + struct proc_fs_info *fs_info; int ret; - proc_apply_options(s, fc, pid_ns, current_user_ns()); + fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL); + if (!fs_info) + return -ENOMEM; + + fs_info->pid_ns = get_pid_ns(ctx->pid_ns); + proc_apply_options(fs_info, fc, current_user_ns()); /* User space would break if executables or devices appear on proc */ s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; @@ -106,6 +111,7 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) s->s_magic = PROC_SUPER_MAGIC; s->s_op = &proc_sops; s->s_time_gran = 1; + s->s_fs_info = fs_info; /* * procfs isn't actually a stacking filesystem; however, there is @@ -113,7 +119,7 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) * top of it */ s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; - + /* procfs dentries and inodes don't require IO to create */ s->s_shrink.seeks = 0; @@ -140,19 +146,17 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) static int proc_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; - struct pid_namespace *pid = sb->s_fs_info; + struct proc_fs_info *fs_info = proc_sb_info(sb); sync_filesystem(sb); - proc_apply_options(sb, fc, pid, current_user_ns()); + proc_apply_options(fs_info, fc, current_user_ns()); return 0; } static int proc_get_tree(struct fs_context *fc) { - struct proc_fs_context *ctx = fc->fs_private; - - return get_tree_keyed(fc, proc_fill_super, ctx->pid_ns); + return get_tree_nodev(fc, proc_fill_super); } static void proc_fs_context_free(struct fs_context *fc) @@ -188,22 +192,17 @@ static int proc_init_fs_context(struct fs_context *fc) static void proc_kill_sb(struct super_block *sb) { - struct pid_namespace *ns; + struct proc_fs_info *fs_info = proc_sb_info(sb); - ns = (struct pid_namespace *)sb->s_fs_info; - if (ns->proc_self) - dput(ns->proc_self); - if (ns->proc_thread_self) - dput(ns->proc_thread_self); - kill_anon_super(sb); + if (fs_info->proc_self) + dput(fs_info->proc_self); - /* Make the pid namespace safe for the next mount of proc */ - ns->proc_self = NULL; - ns->proc_thread_self = NULL; - ns->pid_gid = GLOBAL_ROOT_GID; - ns->hide_pid = 0; + if (fs_info->proc_thread_self) + dput(fs_info->proc_thread_self); - put_pid_ns(ns); + kill_anon_super(sb); + put_pid_ns(fs_info->pid_ns); + kfree(fs_info); } static struct file_system_type proc_fs_type = { diff --git a/fs/proc/self.c b/fs/proc/self.c index 57c0a1047250..309301ac0136 100644 --- a/fs/proc/self.c +++ b/fs/proc/self.c @@ -36,10 +36,10 @@ static unsigned self_inum __ro_after_init; int proc_setup_self(struct super_block *s) { struct inode *root_inode = d_inode(s->s_root); - struct pid_namespace *ns = proc_pid_ns(root_inode); + struct proc_fs_info *fs_info = proc_sb_info(s); struct dentry *self; int ret = -ENOMEM; - + inode_lock(root_inode); self = d_alloc_name(s->s_root, "self"); if (self) { @@ -62,7 +62,7 @@ int proc_setup_self(struct super_block *s) if (ret) pr_err("proc_fill_super: can't allocate /proc/self\n"); else - ns->proc_self = self; + fs_info->proc_self = self; return ret; } diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c index f61ae53533f5..2493cbbdfa6f 100644 --- a/fs/proc/thread_self.c +++ b/fs/proc/thread_self.c @@ -36,7 +36,7 @@ static unsigned thread_self_inum __ro_after_init; int proc_setup_thread_self(struct super_block *s) { struct inode *root_inode = d_inode(s->s_root); - struct pid_namespace *ns = proc_pid_ns(root_inode); + struct proc_fs_info *fs_info = proc_sb_info(s); struct dentry *thread_self; int ret = -ENOMEM; @@ -60,9 +60,9 @@ int proc_setup_thread_self(struct super_block *s) inode_unlock(root_inode); if (ret) - pr_err("proc_fill_super: can't allocate /proc/thread_self\n"); + pr_err("proc_fill_super: can't allocate /proc/thread-self\n"); else - ns->proc_thread_self = thread_self; + fs_info->proc_thread_self = thread_self; return ret; } diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index 4956e362e55e..5a5cb45ac57e 100644 --- a/include/linux/pid_namespace.h +++ b/include/linux/pid_namespace.h @@ -17,12 +17,6 @@ struct fs_pin; -enum { /* definitions for pid_namespace's hide_pid field */ - HIDEPID_OFF = 0, - HIDEPID_NO_ACCESS = 1, - HIDEPID_INVISIBLE = 2, -}; - struct pid_namespace { struct kref kref; struct idr idr; @@ -32,17 +26,11 @@ struct pid_namespace { struct kmem_cache *pid_cachep; unsigned int level; struct pid_namespace *parent; -#ifdef CONFIG_PROC_FS - struct dentry *proc_self; - struct dentry *proc_thread_self; -#endif #ifdef CONFIG_BSD_PROCESS_ACCT struct fs_pin *bacct; #endif struct user_namespace *user_ns; struct ucounts *ucounts; - kgid_t pid_gid; - int hide_pid; int reboot; /* group exit code if this pidns was rebooted */ struct ns_common ns; } __randomize_layout; diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 45c05fd9c99d..1b98a41fdd8a 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -42,6 +42,26 @@ struct proc_ops { unsigned long (*proc_get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); } __randomize_layout; +/* definitions for hide_pid field */ +enum { + HIDEPID_OFF = 0, + HIDEPID_NO_ACCESS = 1, + HIDEPID_INVISIBLE = 2, +}; + +struct proc_fs_info { + struct pid_namespace *pid_ns; + struct dentry *proc_self; /* For /proc/self */ + struct dentry *proc_thread_self; /* For /proc/thread-self */ + kgid_t pid_gid; + int hide_pid; +}; + +static inline struct proc_fs_info *proc_sb_info(struct super_block *sb) +{ + return sb->s_fs_info; +} + #ifdef CONFIG_PROC_FS typedef int (*proc_write_t)(struct file *, char *, size_t); @@ -176,7 +196,7 @@ int open_related_ns(struct ns_common *ns, /* get the associated pid namespace for a file in procfs */ static inline struct pid_namespace *proc_pid_ns(const struct inode *inode) { - return inode->i_sb->s_fs_info; + return proc_sb_info(inode->i_sb)->pid_ns; } #endif /* _LINUX_PROC_FS_H */ diff --git a/tools/testing/selftests/proc/.gitignore b/tools/testing/selftests/proc/.gitignore index 4bca5a9327a4..126901c5d6f4 100644 --- a/tools/testing/selftests/proc/.gitignore +++ b/tools/testing/selftests/proc/.gitignore @@ -3,6 +3,7 @@ /fd-002-posix-eq /fd-003-kthread /proc-loadavg-001 +/proc-multiple-procfs /proc-pid-vm /proc-self-map-files-001 /proc-self-map-files-002 diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile index a8ed0f684829..bf22457256be 100644 --- a/tools/testing/selftests/proc/Makefile +++ b/tools/testing/selftests/proc/Makefile @@ -19,5 +19,6 @@ TEST_GEN_PROGS += self TEST_GEN_PROGS += setns-dcache TEST_GEN_PROGS += setns-sysvipc TEST_GEN_PROGS += thread-self +TEST_GEN_PROGS += proc-multiple-procfs include ../lib.mk diff --git a/tools/testing/selftests/proc/proc-multiple-procfs.c b/tools/testing/selftests/proc/proc-multiple-procfs.c new file mode 100644 index 000000000000..ab912ad95dab --- /dev/null +++ b/tools/testing/selftests/proc/proc-multiple-procfs.c @@ -0,0 +1,48 @@ +/* + * Copyright © 2020 Alexey Gladkov + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ +#include +#include +#include +#include +#include +#include + +int main(void) +{ + struct stat proc_st1, proc_st2; + char procbuff[] = "/tmp/proc.XXXXXX/meminfo"; + char procdir1[] = "/tmp/proc.XXXXXX"; + char procdir2[] = "/tmp/proc.XXXXXX"; + + assert(mkdtemp(procdir1) != NULL); + assert(mkdtemp(procdir2) != NULL); + + assert(!mount("proc", procdir1, "proc", 0, "hidepid=1")); + assert(!mount("proc", procdir2, "proc", 0, "hidepid=2")); + + snprintf(procbuff, sizeof(procbuff), "%s/meminfo", procdir1); + assert(!stat(procbuff, &proc_st1)); + + snprintf(procbuff, sizeof(procbuff), "%s/meminfo", procdir2); + assert(!stat(procbuff, &proc_st2)); + + umount(procdir1); + umount(procdir2); + + assert(proc_st1.st_dev != proc_st2.st_dev); + + return 0; +} From patchwork Sun Apr 19 14:10:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497477 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 06E1C81 for ; Sun, 19 Apr 2020 14:11:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EDAF521841 for ; Sun, 19 Apr 2020 14:11:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726262AbgDSOLq (ORCPT ); Sun, 19 Apr 2020 10:11:46 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45494 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726006AbgDSOLo (ORCPT ); Sun, 19 Apr 2020 10:11:44 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id 5FFAD209FD; Sun, 19 Apr 2020 14:11:41 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 3/7] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Date: Sun, 19 Apr 2020 16:10:53 +0200 Message-Id: <20200419141057.621356-4-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:41 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: If "hidepid=4" mount option is set then do not instantiate pids that we can not ptrace. "hidepid=4" means that procfs should only contain pids that the caller can ptrace. Signed-off-by: Djalal Harouni Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- fs/proc/base.c | 15 +++++++++++++++ fs/proc/root.c | 13 ++++++++++--- include/linux/proc_fs.h | 1 + 3 files changed, 26 insertions(+), 3 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 93b5d05c142c..a52a91e90c25 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -701,6 +701,14 @@ static bool has_pid_permissions(struct proc_fs_info *fs_info, struct task_struct *task, int hide_pid_min) { + /* + * If 'hidpid' mount option is set force a ptrace check, + * we indicate that we are using a filesystem syscall + * by passing PTRACE_MODE_READ_FSCREDS + */ + if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE) + return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); + if (fs_info->hide_pid < hide_pid_min) return true; if (in_group_p(fs_info->pid_gid)) @@ -3319,7 +3327,14 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags) if (!task) goto out; + /* Limit procfs to only ptraceable tasks */ + if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE) { + if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS)) + goto out_put_task; + } + result = proc_pid_instantiate(dentry, task, NULL); +out_put_task: put_task_struct(task); out: return result; diff --git a/fs/proc/root.c b/fs/proc/root.c index 208989274923..8f23b951d685 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -47,6 +47,14 @@ static const struct fs_parameter_spec proc_fs_parameters[] = { {} }; +static inline int valid_hidepid(unsigned int value) +{ + return (value == HIDEPID_OFF || + value == HIDEPID_NO_ACCESS || + value == HIDEPID_INVISIBLE || + value == HIDEPID_NOT_PTRACEABLE); +} + static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) { struct proc_fs_context *ctx = fc->fs_private; @@ -63,10 +71,9 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) break; case Opt_hidepid: + if (!valid_hidepid(result.uint_32)) + return invalf(fc, "proc: unknown value of hidepid.\n"); ctx->hidepid = result.uint_32; - if (ctx->hidepid < HIDEPID_OFF || - ctx->hidepid > HIDEPID_INVISIBLE) - return invalfc(fc, "hidepid value must be between 0 and 2.\n"); break; default: diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 1b98a41fdd8a..5bdc117ae947 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -47,6 +47,7 @@ enum { HIDEPID_OFF = 0, HIDEPID_NO_ACCESS = 1, HIDEPID_INVISIBLE = 2, + HIDEPID_NOT_PTRACEABLE = 4, /* Limit pids to only ptraceable pids */ }; struct proc_fs_info { From patchwork Sun Apr 19 14:10:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497495 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9B52681 for ; Sun, 19 Apr 2020 14:12:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C0B321974 for ; Sun, 19 Apr 2020 14:12:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726447AbgDSOMD (ORCPT ); Sun, 19 Apr 2020 10:12:03 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45528 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725905AbgDSOLq (ORCPT ); Sun, 19 Apr 2020 10:11:46 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id 233A7209FE; Sun, 19 Apr 2020 14:11:42 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 4/7] proc: add option to mount only a pids subset Date: Sun, 19 Apr 2020 16:10:54 +0200 Message-Id: <20200419141057.621356-5-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:42 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: This allows to hide all files and directories in the procfs that are not related to tasks. Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- fs/proc/generic.c | 9 +++++++++ fs/proc/inode.c | 6 ++++++ fs/proc/root.c | 33 +++++++++++++++++++++++++++++++++ include/linux/proc_fs.h | 7 +++++++ 4 files changed, 55 insertions(+) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 4ed6dabdf6ff..2f9fa179194d 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -269,6 +269,11 @@ struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry, struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { + struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb); + + if (fs_info->pidonly == PROC_PIDONLY_ON) + return ERR_PTR(-ENOENT); + return proc_lookup_de(dir, dentry, PDE(dir)); } @@ -325,6 +330,10 @@ int proc_readdir_de(struct file *file, struct dir_context *ctx, int proc_readdir(struct file *file, struct dir_context *ctx) { struct inode *inode = file_inode(file); + struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb); + + if (fs_info->pidonly == PROC_PIDONLY_ON) + return 1; return proc_readdir_de(file, ctx, PDE(inode)); } diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 9c756531282a..0d5e68fa842f 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -173,6 +173,8 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root) seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid)); if (fs_info->hide_pid != HIDEPID_OFF) seq_printf(seq, ",hidepid=%u", fs_info->hide_pid); + if (fs_info->pidonly != PROC_PIDONLY_OFF) + seq_printf(seq, ",subset=pid"); return 0; } @@ -463,6 +465,7 @@ proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr, static int proc_reg_open(struct inode *inode, struct file *file) { + struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb); struct proc_dir_entry *pde = PDE(inode); int rv = 0; typeof_member(struct proc_ops, proc_open) open; @@ -476,6 +479,9 @@ static int proc_reg_open(struct inode *inode, struct file *file) return rv; } + if (fs_info->pidonly == PROC_PIDONLY_ON) + return -ENOENT; + /* * Ensure that * 1) PDE's ->release hook will be called no matter what diff --git a/fs/proc/root.c b/fs/proc/root.c index 8f23b951d685..baff006a918f 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -34,16 +34,19 @@ struct proc_fs_context { unsigned int mask; int hidepid; int gid; + int pidonly; }; enum proc_param { Opt_gid, Opt_hidepid, + Opt_subset, }; static const struct fs_parameter_spec proc_fs_parameters[] = { fsparam_u32("gid", Opt_gid), fsparam_u32("hidepid", Opt_hidepid), + fsparam_string("subset", Opt_subset), {} }; @@ -55,6 +58,29 @@ static inline int valid_hidepid(unsigned int value) value == HIDEPID_NOT_PTRACEABLE); } +static int proc_parse_subset_param(struct fs_context *fc, char *value) +{ + struct proc_fs_context *ctx = fc->fs_private; + + while (value) { + char *ptr = strchr(value, ','); + + if (ptr != NULL) + *ptr++ = '\0'; + + if (*value != '\0') { + if (!strcmp(value, "pid")) { + ctx->pidonly = PROC_PIDONLY_ON; + } else { + return invalf(fc, "proc: unsupported subset option - %s\n", value); + } + } + value = ptr; + } + + return 0; +} + static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) { struct proc_fs_context *ctx = fc->fs_private; @@ -76,6 +102,11 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) ctx->hidepid = result.uint_32; break; + case Opt_subset: + if (proc_parse_subset_param(fc, param->string) < 0) + return -EINVAL; + break; + default: return -EINVAL; } @@ -94,6 +125,8 @@ static void proc_apply_options(struct proc_fs_info *fs_info, fs_info->pid_gid = make_kgid(user_ns, ctx->gid); if (ctx->mask & (1 << Opt_hidepid)) fs_info->hide_pid = ctx->hidepid; + if (ctx->mask & (1 << Opt_subset)) + fs_info->pidonly = ctx->pidonly; } static int proc_fill_super(struct super_block *s, struct fs_context *fc) diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 5bdc117ae947..8bc31ba5cd9c 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -50,12 +50,19 @@ enum { HIDEPID_NOT_PTRACEABLE = 4, /* Limit pids to only ptraceable pids */ }; +/* definitions for proc mount option pidonly */ +enum { + PROC_PIDONLY_OFF = 0, + PROC_PIDONLY_ON = 1, +}; + struct proc_fs_info { struct pid_namespace *pid_ns; struct dentry *proc_self; /* For /proc/self */ struct dentry *proc_thread_self; /* For /proc/thread-self */ kgid_t pid_gid; int hide_pid; + int pidonly; }; static inline struct proc_fs_info *proc_sb_info(struct super_block *sb) From patchwork Sun Apr 19 14:10:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497481 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E6F2213B2 for ; Sun, 19 Apr 2020 14:11:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D927721974 for ; Sun, 19 Apr 2020 14:11:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726372AbgDSOLt (ORCPT ); Sun, 19 Apr 2020 10:11:49 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45564 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726157AbgDSOLr (ORCPT ); Sun, 19 Apr 2020 10:11:47 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id ED324209FF; Sun, 19 Apr 2020 14:11:42 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 5/7] docs: proc: add documentation for "hidepid=4" and "subset=pid" options and new mount behavior Date: Sun, 19 Apr 2020 16:10:55 +0200 Message-Id: <20200419141057.621356-6-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:43 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- Documentation/filesystems/proc.rst | 54 ++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 38b606991065..360486c7a992 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -51,6 +51,8 @@ fixes/update part 1.1 Stefani Seibold June 9 2009 4 Configuring procfs 4.1 Mount options + 5 Filesystem behavior + Preface ======= @@ -2142,6 +2144,7 @@ The following mount options are supported: ========= ======================================================== hidepid= Set /proc// access mode. gid= Set the group authorized to learn processes information. + subset= Show only the specified subset of procfs. ========= ======================================================== hidepid=0 means classic mode - everybody may access all /proc// directories @@ -2164,6 +2167,57 @@ information about running processes, whether some daemon runs with elevated privileges, whether other user runs some sensitive program, whether other users run any program at all, etc. +hidepid=4 means that procfs should only contain /proc// directories +that the caller can ptrace. + gid= defines a group authorized to learn processes information otherwise prohibited by hidepid=. If you use some daemon like identd which needs to learn information about processes information, just add identd to this group. + +subset=pid hides all top level files and directories in the procfs that +are not related to tasks. + +5 Filesystem behavior +---------------------------- + +Originally, before the advent of pid namepsace, procfs was a global file +system. It means that there was only one procfs instance in the system. + +When pid namespace was added, a separate procfs instance was mounted in +each pid namespace. So, procfs mount options are global among all +mountpoints within the same namespace. + +:: + +# grep ^proc /proc/mounts +proc /proc proc rw,relatime,hidepid=2 0 0 + +# strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc +mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0 ++++ exited with 0 +++ + +# grep ^proc /proc/mounts +proc /proc proc rw,relatime,hidepid=2 0 0 +proc /tmp/proc proc rw,relatime,hidepid=2 0 0 + +and only after remounting procfs mount options will change at all +mountpoints. + +# mount -o remount,hidepid=1 -t proc proc /tmp/proc + +# grep ^proc /proc/mounts +proc /proc proc rw,relatime,hidepid=1 0 0 +proc /tmp/proc proc rw,relatime,hidepid=1 0 0 + +This behavior is different from the behavior of other filesystems. + +The new procfs behavior is more like other filesystems. Each procfs mount +creates a new procfs instance. Mount options affect own procfs instance. +It means that it became possible to have several procfs instances +displaying tasks with different filtering options in one pid namespace. + +# mount -o hidepid=2 -t proc proc /proc +# mount -o hidepid=1 -t proc proc /tmp/proc +# grep ^proc /proc/mounts +proc /proc proc rw,relatime,hidepid=2 0 0 +proc /tmp/proc proc rw,relatime,hidepid=1 0 0 From patchwork Sun Apr 19 14:10:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497491 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 42A301667 for ; Sun, 19 Apr 2020 14:12:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29E3A21974 for ; Sun, 19 Apr 2020 14:12:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726400AbgDSOLx (ORCPT ); Sun, 19 Apr 2020 10:11:53 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45592 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726160AbgDSOLs (ORCPT ); Sun, 19 Apr 2020 10:11:48 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id BA05E20A00; Sun, 19 Apr 2020 14:11:43 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 6/7] proc: use human-readable values for hidepid Date: Sun, 19 Apr 2020 16:10:56 +0200 Message-Id: <20200419141057.621356-7-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:44 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: The hidepid parameter values are becoming more and more and it becomes difficult to remember what each new magic number means. Backward compatibility is preserved since it is possible to specify numerical value for the hidepid parameter. This does not break the fsconfig since it is not possible to specify a numerical value through it. All numeric values are converted to a string. The type FSCONFIG_SET_BINARY cannot be used to indicate a numerical value. Selftest has been added to verify this behavior. Suggested-by: Andy Lutomirski Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- Documentation/filesystems/proc.rst | 52 +++++++++---------- fs/proc/inode.c | 15 +++++- fs/proc/root.c | 38 ++++++++++++-- tools/testing/selftests/proc/.gitignore | 1 + tools/testing/selftests/proc/Makefile | 1 + .../selftests/proc/proc-fsconfig-hidepid.c | 50 ++++++++++++++++++ 6 files changed, 126 insertions(+), 31 deletions(-) create mode 100644 tools/testing/selftests/proc/proc-fsconfig-hidepid.c diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 360486c7a992..e2ecf248feb5 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -2147,28 +2147,28 @@ The following mount options are supported: subset= Show only the specified subset of procfs. ========= ======================================================== -hidepid=0 means classic mode - everybody may access all /proc// directories -(default). - -hidepid=1 means users may not access any /proc// directories but their -own. Sensitive files like cmdline, sched*, status are now protected against -other users. This makes it impossible to learn whether any user runs -specific program (given the program doesn't reveal itself by its behaviour). -As an additional bonus, as /proc//cmdline is unaccessible for other users, -poorly written programs passing sensitive information via program arguments are -now protected against local eavesdroppers. - -hidepid=2 means hidepid=1 plus all /proc// will be fully invisible to other -users. It doesn't mean that it hides a fact whether a process with a specific -pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), -but it hides process' uid and gid, which may be learned by stat()'ing -/proc// otherwise. It greatly complicates an intruder's task of gathering -information about running processes, whether some daemon runs with elevated -privileges, whether other user runs some sensitive program, whether other users -run any program at all, etc. - -hidepid=4 means that procfs should only contain /proc// directories -that the caller can ptrace. +hidepid=off or hidepid=0 means classic mode - everybody may access all +/proc// directories (default). + +hidepid=noaccess or hidepid=1 means users may not access any /proc// +directories but their own. Sensitive files like cmdline, sched*, status are now +protected against other users. This makes it impossible to learn whether any +user runs specific program (given the program doesn't reveal itself by its +behaviour). As an additional bonus, as /proc//cmdline is unaccessible for +other users, poorly written programs passing sensitive information via program +arguments are now protected against local eavesdroppers. + +hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc// will be +fully invisible to other users. It doesn't mean that it hides a fact whether a +process with a specific pid value exists (it can be learned by other means, e.g. +by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by +stat()'ing /proc// otherwise. It greatly complicates an intruder's task of +gathering information about running processes, whether some daemon runs with +elevated privileges, whether other user runs some sensitive program, whether +other users run any program at all, etc. + +hidepid=ptraceable or hidepid=4 means that procfs should only contain +/proc// directories that the caller can ptrace. gid= defines a group authorized to learn processes information otherwise prohibited by hidepid=. If you use some daemon like identd which needs to learn @@ -2216,8 +2216,8 @@ creates a new procfs instance. Mount options affect own procfs instance. It means that it became possible to have several procfs instances displaying tasks with different filtering options in one pid namespace. -# mount -o hidepid=2 -t proc proc /proc -# mount -o hidepid=1 -t proc proc /tmp/proc +# mount -o hidepid=invisible -t proc proc /proc +# mount -o hidepid=noaccess -t proc proc /tmp/proc # grep ^proc /proc/mounts -proc /proc proc rw,relatime,hidepid=2 0 0 -proc /tmp/proc proc rw,relatime,hidepid=1 0 0 +proc /proc proc rw,relatime,hidepid=invisible 0 0 +proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 0d5e68fa842f..cbacac2e892b 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -24,6 +24,7 @@ #include #include #include +#include #include @@ -165,6 +166,18 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock deactivate_super(old_sb); } +static inline const char *hidepid2str(int v) +{ + switch (v) { + case HIDEPID_OFF: return "off"; + case HIDEPID_NO_ACCESS: return "noaccess"; + case HIDEPID_INVISIBLE: return "invisible"; + case HIDEPID_NOT_PTRACEABLE: return "ptraceable"; + } + WARN_ONCE(1, "bad hide_pid value: %d\n", v); + return "unknown"; +} + static int proc_show_options(struct seq_file *seq, struct dentry *root) { struct proc_fs_info *fs_info = proc_sb_info(root->d_sb); @@ -172,7 +185,7 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root) if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID)) seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid)); if (fs_info->hide_pid != HIDEPID_OFF) - seq_printf(seq, ",hidepid=%u", fs_info->hide_pid); + seq_printf(seq, ",hidepid=%s", hidepid2str(fs_info->hide_pid)); if (fs_info->pidonly != PROC_PIDONLY_OFF) seq_printf(seq, ",subset=pid"); diff --git a/fs/proc/root.c b/fs/proc/root.c index baff006a918f..288093261b7f 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -45,7 +45,7 @@ enum proc_param { static const struct fs_parameter_spec proc_fs_parameters[] = { fsparam_u32("gid", Opt_gid), - fsparam_u32("hidepid", Opt_hidepid), + fsparam_string("hidepid", Opt_hidepid), fsparam_string("subset", Opt_subset), {} }; @@ -58,6 +58,37 @@ static inline int valid_hidepid(unsigned int value) value == HIDEPID_NOT_PTRACEABLE); } +static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct proc_fs_context *ctx = fc->fs_private; + struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid); + struct fs_parse_result result; + int base = (unsigned long)hidepid_u32_spec.data; + + if (param->type != fs_value_is_string) + return invalf(fc, "proc: unexpected type of hidepid value\n"); + + if (!kstrtouint(param->string, base, &result.uint_32)) { + if (!valid_hidepid(result.uint_32)) + return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); + ctx->hidepid = result.uint_32; + return 0; + } + + if (!strcmp(param->string, "off")) + ctx->hidepid = HIDEPID_OFF; + else if (!strcmp(param->string, "noaccess")) + ctx->hidepid = HIDEPID_NO_ACCESS; + else if (!strcmp(param->string, "invisible")) + ctx->hidepid = HIDEPID_INVISIBLE; + else if (!strcmp(param->string, "ptraceable")) + ctx->hidepid = HIDEPID_NOT_PTRACEABLE; + else + return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); + + return 0; +} + static int proc_parse_subset_param(struct fs_context *fc, char *value) { struct proc_fs_context *ctx = fc->fs_private; @@ -97,9 +128,8 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) break; case Opt_hidepid: - if (!valid_hidepid(result.uint_32)) - return invalf(fc, "proc: unknown value of hidepid.\n"); - ctx->hidepid = result.uint_32; + if (proc_parse_hidepid_param(fc, param)) + return -EINVAL; break; case Opt_subset: diff --git a/tools/testing/selftests/proc/.gitignore b/tools/testing/selftests/proc/.gitignore index 126901c5d6f4..bed4b5318a86 100644 --- a/tools/testing/selftests/proc/.gitignore +++ b/tools/testing/selftests/proc/.gitignore @@ -2,6 +2,7 @@ /fd-001-lookup /fd-002-posix-eq /fd-003-kthread +/proc-fsconfig-hidepid /proc-loadavg-001 /proc-multiple-procfs /proc-pid-vm diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile index bf22457256be..8be8a03d2973 100644 --- a/tools/testing/selftests/proc/Makefile +++ b/tools/testing/selftests/proc/Makefile @@ -20,5 +20,6 @@ TEST_GEN_PROGS += setns-dcache TEST_GEN_PROGS += setns-sysvipc TEST_GEN_PROGS += thread-self TEST_GEN_PROGS += proc-multiple-procfs +TEST_GEN_PROGS += proc-fsconfig-hidepid include ../lib.mk diff --git a/tools/testing/selftests/proc/proc-fsconfig-hidepid.c b/tools/testing/selftests/proc/proc-fsconfig-hidepid.c new file mode 100644 index 000000000000..b9af8f537185 --- /dev/null +++ b/tools/testing/selftests/proc/proc-fsconfig-hidepid.c @@ -0,0 +1,50 @@ +/* + * Copyright © 2020 Alexey Gladkov + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ +#include +#include +#include +#include +#include +#include + +static inline int fsopen(const char *fsname, unsigned int flags) +{ + return syscall(__NR_fsopen, fsname, flags); +} + +static inline int fsconfig(int fd, unsigned int cmd, const char *key, const void *val, int aux) +{ + return syscall(__NR_fsconfig, fd, cmd, key, val, aux); +} + +int main(void) +{ + int fsfd, ret; + int hidepid = 2; + + assert((fsfd = fsopen("proc", 0)) != -1); + + ret = fsconfig(fsfd, FSCONFIG_SET_BINARY, "hidepid", &hidepid, 0); + assert(ret == -1); + assert(errno == EINVAL); + + assert(!fsconfig(fsfd, FSCONFIG_SET_STRING, "hidepid", "2", 0)); + assert(!fsconfig(fsfd, FSCONFIG_SET_STRING, "hidepid", "invisible", 0)); + + assert(!close(fsfd)); + + return 0; +} From patchwork Sun Apr 19 14:10:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11497487 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A50BB81 for ; Sun, 19 Apr 2020 14:12:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 915E721974 for ; Sun, 19 Apr 2020 14:12:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726409AbgDSOLx (ORCPT ); Sun, 19 Apr 2020 10:11:53 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:45624 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726167AbgDSOLs (ORCPT ); Sun, 19 Apr 2020 10:11:48 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id 8629720A01; Sun, 19 Apr 2020 14:11:44 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , David Howells Subject: [PATCH v12 7/7] proc: use named enums for better readability Date: Sun, 19 Apr 2020 16:10:57 +0200 Message-Id: <20200419141057.621356-8-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200419141057.621356-1-gladkov.alexey@gmail.com> References: <20200419141057.621356-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Sun, 19 Apr 2020 14:11:45 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Signed-off-by: Alexey Gladkov Reviewed-by: Alexey Dobriyan Reviewed-by: Kees Cook --- fs/proc/base.c | 2 +- fs/proc/inode.c | 2 +- fs/proc/root.c | 4 ++-- include/linux/proc_fs.h | 8 ++++---- 4 files changed, 8 insertions(+), 8 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index a52a91e90c25..2868bff1a142 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -699,7 +699,7 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr) */ static bool has_pid_permissions(struct proc_fs_info *fs_info, struct task_struct *task, - int hide_pid_min) + enum proc_hidepid hide_pid_min) { /* * If 'hidpid' mount option is set force a ptrace check, diff --git a/fs/proc/inode.c b/fs/proc/inode.c index cbacac2e892b..f40c2532c057 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -166,7 +166,7 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock deactivate_super(old_sb); } -static inline const char *hidepid2str(int v) +static inline const char *hidepid2str(enum proc_hidepid v) { switch (v) { case HIDEPID_OFF: return "off"; diff --git a/fs/proc/root.c b/fs/proc/root.c index 288093261b7f..ffebed1999e5 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -32,9 +32,9 @@ struct proc_fs_context { struct pid_namespace *pid_ns; unsigned int mask; - int hidepid; + enum proc_hidepid hidepid; int gid; - int pidonly; + enum proc_pidonly pidonly; }; enum proc_param { diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 8bc31ba5cd9c..2cb424e6f36a 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -43,7 +43,7 @@ struct proc_ops { } __randomize_layout; /* definitions for hide_pid field */ -enum { +enum proc_hidepid { HIDEPID_OFF = 0, HIDEPID_NO_ACCESS = 1, HIDEPID_INVISIBLE = 2, @@ -51,7 +51,7 @@ enum { }; /* definitions for proc mount option pidonly */ -enum { +enum proc_pidonly { PROC_PIDONLY_OFF = 0, PROC_PIDONLY_ON = 1, }; @@ -61,8 +61,8 @@ struct proc_fs_info { struct dentry *proc_self; /* For /proc/self */ struct dentry *proc_thread_self; /* For /proc/thread-self */ kgid_t pid_gid; - int hide_pid; - int pidonly; + enum proc_hidepid hide_pid; + enum proc_pidonly pidonly; }; static inline struct proc_fs_info *proc_sb_info(struct super_block *sb)