From patchwork Thu Dec 21 22:38:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13502737 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5552B11719; Thu, 21 Dec 2023 22:37:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03679C433C7; Thu, 21 Dec 2023 22:37:08 +0000 (UTC) Date: Thu, 21 Dec 2023 17:38:12 -0500 From: Steven Rostedt To: LKML Cc: Linux Trace Kernel , Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Linus Torvalds , Dongliang Cui , Hongyu Jin Subject: [PATCH] eventfs: Fix file and directory uid and gid ownership Message-ID: <20231221173812.51fe6113@gandalf.local.home> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" It was reported that when mounting the tracefs file system with a gid other than root, the ownership did not carry down to the eventfs directory due to the dynamic nature of it. A fix was done to solve this, but it had two issues. (a) if the attr passed into update_inode_attr() was NULL, it didn't do anything. This is true for files that have not had a chown or chgrp done to itself or any of its sibling files, as the attr is allocated for all children when any one needs it. # umount /sys/kernel/tracing # mount -o rw,seclabel,relatime,gid=1000 -t tracefs nodev /mnt # ls -ld /mnt/events/sched drwxr-xr-x 28 root rostedt 0 Dec 21 13:12 /mnt/events/sched/ # ls -ld /mnt/events/sched/sched_switch drwxr-xr-x 2 root rostedt 0 Dec 21 13:12 /mnt/events/sched/sched_switch/ But when checking the files: # ls -l /mnt/events/sched/sched_switch total 0 -rw-r----- 1 root root 0 Dec 21 13:12 enable -rw-r----- 1 root root 0 Dec 21 13:12 filter -r--r----- 1 root root 0 Dec 21 13:12 format -r--r----- 1 root root 0 Dec 21 13:12 hist -r--r----- 1 root root 0 Dec 21 13:12 id -rw-r----- 1 root root 0 Dec 21 13:12 trigger (b) When the attr does not denote the UID or GID, it defaulted to using the parent uid or gid. This is incorrect as changing the parent uid or gid will automatically change all its children. # chgrp tracing /mnt/events/timer # ls -ld /mnt/events/timer drwxr-xr-x 2 root tracing 0 Dec 21 14:34 /mnt/events/timer # ls -l /mnt/events/timer total 0 -rw-r----- 1 root root 0 Dec 21 14:35 enable -rw-r----- 1 root root 0 Dec 21 14:35 filter drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_cancel drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_expire_entry drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_expire_exit drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_init drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_start drwxr-xr-x 2 root tracing 0 Dec 21 14:35 itimer_expire drwxr-xr-x 2 root tracing 0 Dec 21 14:35 itimer_state drwxr-xr-x 2 root tracing 0 Dec 21 14:35 tick_stop drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_cancel drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_expire_entry drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_expire_exit drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_init drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_start At first it was thought that this could be easily fixed by just making the default ownership of the superblock when it was mounted. But this does not handle the case of: # chgrp tracing instances # mkdir instances/foo If the superblock was used, then the group ownership would be that of what it was when it was mounted, when it should instead be "tracing". Instead, set a flag for the top level eventfs directory ("events") to flag which eventfs_inode belongs to it. Since the "events" directory's dentry and inode are never freed, it does not need to use its attr field to restore its mode and ownership. Use the this eventfs_inode's attr as the default ownership for all the files and directories underneath it. When the events eventfs_inode is created, it sets its ownership to its parent uid and gid. As the events directory is created at boot up before it gets mounted, this will always be uid=0 and gid=0. If it's created via an instance, then it will take the ownership of the instance directory. When the file system is mounted, it will update all the gids if one is specified. This will have a callback to update the events evenfs_inode's default entries. When a file or directory is created under the events directory, it will walk the ei->dentry parents until it finds the evenfs_inode that belongs to the events directory to retrieve the default uid and gid values. Link: https://lore.kernel.org/all/CAHk-=wiwQtUHvzwyZucDq8=Gtw+AnwScyLhpFswrQ84PjhoGsg@mail.gmail.com/ Cc: stable@vger.kernel.org Fixes: 0dfc852b6fe3 ("eventfs: Have event files and directories default to parent uid and gid") Reported-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/event_inode.c | 74 ++++++++++++++++++++++++++++++++++------ fs/tracefs/inode.c | 6 ++++ fs/tracefs/internal.h | 2 ++ 3 files changed, 72 insertions(+), 10 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 2ccc849a5bda..2d6b11195420 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -113,7 +113,14 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry, * determined by the parent directory. */ if (dentry->d_inode->i_mode & S_IFDIR) { - update_attr(&ei->attr, iattr); + /* + * The events directory dentry is never freed, unless its + * part of an instance that is deleted. It's attr is the + * default for its child files and directores. + * Do not update it. It's not used for its own mode or ownership + */ + if (!ei->is_events) + update_attr(&ei->attr, iattr); } else { name = dentry->d_name.name; @@ -148,28 +155,62 @@ static const struct file_operations eventfs_file_operations = { .release = eventfs_release, }; +/* Return the evenfs_inode of the "events" directory */ +static struct eventfs_inode *eventfs_find_events(struct dentry *dentry) +{ + struct eventfs_inode *ei; + + mutex_lock(&eventfs_mutex); + do { + /* The parent always has an ei, except for events itself */ + ei = dentry->d_parent->d_fsdata; + + /* + * If the ei is being freed, the ownership of the children + * doesn't matter. + */ + if (ei->is_freed) { + ei = NULL; + break; + } + + dentry = ei->dentry; + } while (!ei->is_events); + mutex_unlock(&eventfs_mutex); + + return ei; +} + static void update_inode_attr(struct dentry *dentry, struct inode *inode, struct eventfs_attr *attr, umode_t mode) { - if (!attr) { - inode->i_mode = mode; + struct eventfs_inode *events_ei = eventfs_find_events(dentry); + + if (!events_ei) + return; + + inode->i_mode = mode; + inode->i_uid = events_ei->attr.uid; + inode->i_gid = events_ei->attr.gid; + + if (!attr) return; - } if (attr->mode & EVENTFS_SAVE_MODE) inode->i_mode = attr->mode & EVENTFS_MODE_MASK; - else - inode->i_mode = mode; if (attr->mode & EVENTFS_SAVE_UID) inode->i_uid = attr->uid; - else - inode->i_uid = d_inode(dentry->d_parent)->i_uid; if (attr->mode & EVENTFS_SAVE_GID) inode->i_gid = attr->gid; - else - inode->i_gid = d_inode(dentry->d_parent)->i_gid; +} + +void eventfs_update_gid(struct dentry *dentry, kgid_t gid) +{ + struct eventfs_inode *ei = dentry->d_fsdata; + + ei->attr.gid = gid; } /** @@ -860,6 +901,8 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry struct eventfs_inode *ei; struct tracefs_inode *ti; struct inode *inode; + kuid_t uid; + kgid_t gid; if (security_locked_down(LOCKDOWN_TRACEFS)) return NULL; @@ -884,11 +927,20 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry ei->dentry = dentry; ei->entries = entries; ei->nr_entries = size; + ei->is_events = 1; ei->data = data; ei->name = kstrdup_const(name, GFP_KERNEL); if (!ei->name) goto fail; + /* Save the ownership of this directory */ + uid = d_inode(dentry->d_parent)->i_uid; + gid = d_inode(dentry->d_parent)->i_gid; + + /* This is used as the default ownership of the files and directories */ + ei->attr.uid = uid; + ei->attr.gid = gid; + INIT_LIST_HEAD(&ei->children); INIT_LIST_HEAD(&ei->list); @@ -897,6 +949,8 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry ti->private = ei; inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; + inode->i_uid = uid; + inode->i_gid = gid; inode->i_op = &eventfs_root_dir_inode_operations; inode->i_fop = &eventfs_file_operations; diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index ae648deed019..62524b20964e 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -210,6 +210,7 @@ static void set_gid(struct dentry *parent, kgid_t gid) next = this_parent->d_subdirs.next; resume: while (next != &this_parent->d_subdirs) { + struct tracefs_inode *ti; struct list_head *tmp = next; struct dentry *dentry = list_entry(tmp, struct dentry, d_child); next = tmp->next; @@ -218,6 +219,11 @@ static void set_gid(struct dentry *parent, kgid_t gid) change_gid(dentry, gid); + /* If this is the events directory, update that too */ + ti = get_tracefs(dentry->d_inode); + if (ti && (ti->flags & TRACEFS_EVENT_INODE)) + eventfs_update_gid(dentry, gid); + if (!list_empty(&dentry->d_subdirs)) { spin_unlock(&this_parent->d_lock); spin_release(&dentry->d_lock.dep_map, _RET_IP_); diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index ccee18ca66c7..899e447778ac 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -62,6 +62,7 @@ struct eventfs_inode { struct rcu_head rcu; }; unsigned int is_freed:1; + unsigned int is_events:1; unsigned int nr_entries:31; }; @@ -77,6 +78,7 @@ struct inode *tracefs_get_inode(struct super_block *sb); struct dentry *eventfs_start_creating(const char *name, struct dentry *parent); struct dentry *eventfs_failed_creating(struct dentry *dentry); struct dentry *eventfs_end_creating(struct dentry *dentry); +void eventfs_update_gid(struct dentry *dentry, kgid_t gid); void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry); #endif /* _TRACEFS_INTERNAL_H */