| Message ID | 20190822051633.12980-1-ebiggers@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfs: set fs_context::user_ns for reconfigure | expand |
On Wed, Aug 21, 2019 at 10:16:33PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > fs_context::user_ns is used by fuse_parse_param(), even during remount, > so it needs to be set to the existing value for reconfigure. > > Reproducer: > > #include <fcntl.h> > #include <sys/mount.h> > > int main() > { > char opts[128]; > int fd = open("/dev/fuse", O_RDWR); > > sprintf(opts, "fd=%d,rootmode=040000,user_id=0,group_id=0", fd); > mkdir("mnt", 0777); > mount("foo", "mnt", "fuse.foo", 0, opts); > mount("foo", "mnt", "fuse.foo", MS_REMOUNT, opts); > } > > Crash: > BUG: kernel NULL pointer dereference, address: 0000000000000000 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] SMP > CPU: 0 PID: 129 Comm: syz_make_kuid Not tainted 5.3.0-rc5-next-20190821 #3 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014 > RIP: 0010:map_id_range_down+0xb/0xc0 kernel/user_namespace.c:291 > [...] > Call Trace: > map_id_down kernel/user_namespace.c:312 [inline] > make_kuid+0xe/0x10 kernel/user_namespace.c:389 > fuse_parse_param+0x116/0x210 fs/fuse/inode.c:523 > vfs_parse_fs_param+0xdb/0x1b0 fs/fs_context.c:145 > vfs_parse_fs_string+0x6a/0xa0 fs/fs_context.c:188 > generic_parse_monolithic+0x85/0xc0 fs/fs_context.c:228 > parse_monolithic_mount_data+0x1b/0x20 fs/fs_context.c:708 > do_remount fs/namespace.c:2525 [inline] > do_mount+0x39a/0xa60 fs/namespace.c:3107 > ksys_mount+0x7d/0xd0 fs/namespace.c:3325 > __do_sys_mount fs/namespace.c:3339 [inline] > __se_sys_mount fs/namespace.c:3336 [inline] > __x64_sys_mount+0x20/0x30 fs/namespace.c:3336 > do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com > Fixes: 408cbe695350 ("vfs: Convert fuse to use the new mount API") > Cc: David Howells <dhowells@redhat.com> > Cc: Miklos Szeredi <miklos@szeredi.hu> > Signed-off-by: Eric Biggers <ebiggers@google.com> > --- > fs/fs_context.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/fs/fs_context.c b/fs/fs_context.c > index cc61d305dc4b..44c4174b250a 100644 > --- a/fs/fs_context.c > +++ b/fs/fs_context.c > @@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type, > fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); > break; > case FS_CONTEXT_FOR_RECONFIGURE: > - /* We don't pin any namespaces as the superblock's > - * subscriptions cannot be changed at this point. > - */ > atomic_inc(&reference->d_sb->s_active); > + fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); > fc->root = dget(reference); > break; > } > -- > 2.22.1 Ping.
On Fri, Aug 30, 2019 at 10:12:28PM -0500, Eric Biggers wrote: > On Wed, Aug 21, 2019 at 10:16:33PM -0700, Eric Biggers wrote: > > From: Eric Biggers <ebiggers@google.com> > > > > fs_context::user_ns is used by fuse_parse_param(), even during remount, > > so it needs to be set to the existing value for reconfigure. > > > > Reproducer: > > > > #include <fcntl.h> > > #include <sys/mount.h> > > > > int main() > > { > > char opts[128]; > > int fd = open("/dev/fuse", O_RDWR); > > > > sprintf(opts, "fd=%d,rootmode=040000,user_id=0,group_id=0", fd); > > mkdir("mnt", 0777); > > mount("foo", "mnt", "fuse.foo", 0, opts); > > mount("foo", "mnt", "fuse.foo", MS_REMOUNT, opts); > > } > > > > Crash: > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > > #PF: supervisor read access in kernel mode > > #PF: error_code(0x0000) - not-present page > > PGD 0 P4D 0 > > Oops: 0000 [#1] SMP > > CPU: 0 PID: 129 Comm: syz_make_kuid Not tainted 5.3.0-rc5-next-20190821 #3 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014 > > RIP: 0010:map_id_range_down+0xb/0xc0 kernel/user_namespace.c:291 > > [...] > > Call Trace: > > map_id_down kernel/user_namespace.c:312 [inline] > > make_kuid+0xe/0x10 kernel/user_namespace.c:389 > > fuse_parse_param+0x116/0x210 fs/fuse/inode.c:523 > > vfs_parse_fs_param+0xdb/0x1b0 fs/fs_context.c:145 > > vfs_parse_fs_string+0x6a/0xa0 fs/fs_context.c:188 > > generic_parse_monolithic+0x85/0xc0 fs/fs_context.c:228 > > parse_monolithic_mount_data+0x1b/0x20 fs/fs_context.c:708 > > do_remount fs/namespace.c:2525 [inline] > > do_mount+0x39a/0xa60 fs/namespace.c:3107 > > ksys_mount+0x7d/0xd0 fs/namespace.c:3325 > > __do_sys_mount fs/namespace.c:3339 [inline] > > __se_sys_mount fs/namespace.c:3336 [inline] > > __x64_sys_mount+0x20/0x30 fs/namespace.c:3336 > > do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com > > Fixes: 408cbe695350 ("vfs: Convert fuse to use the new mount API") > > Cc: David Howells <dhowells@redhat.com> > > Cc: Miklos Szeredi <miklos@szeredi.hu> > > Signed-off-by: Eric Biggers <ebiggers@google.com> > > --- > > fs/fs_context.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/fs/fs_context.c b/fs/fs_context.c > > index cc61d305dc4b..44c4174b250a 100644 > > --- a/fs/fs_context.c > > +++ b/fs/fs_context.c > > @@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type, > > fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); > > break; > > case FS_CONTEXT_FOR_RECONFIGURE: > > - /* We don't pin any namespaces as the superblock's > > - * subscriptions cannot be changed at this point. > > - */ > > atomic_inc(&reference->d_sb->s_active); > > + fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); > > fc->root = dget(reference); > > break; > > } > > -- > > 2.22.1 > > Ping. > Ping. This is still broken in linux-next. - Eric
diff --git a/fs/fs_context.c b/fs/fs_context.c index cc61d305dc4b..44c4174b250a 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type, fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); break; case FS_CONTEXT_FOR_RECONFIGURE: - /* We don't pin any namespaces as the superblock's - * subscriptions cannot be changed at this point. - */ atomic_inc(&reference->d_sb->s_active); + fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); fc->root = dget(reference); break; }