| Message ID | 20240829083409.3788142-1-libaokun@huaweicloud.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] cachefiles: fix dentry leak in cachefiles_open_file() | expand |
libaokun@huaweicloud.com wrote: > From: Baokun Li <libaokun1@huawei.com> > > A dentry leak may be caused when a lookup cookie and a cull are concurrent: > > P1 | P2 > ----------------------------------------------------------- > cachefiles_lookup_cookie > cachefiles_look_up_object > lookup_one_positive_unlocked > // get dentry > cachefiles_cull > inode->i_flags |= S_KERNEL_FILE; > cachefiles_open_file > cachefiles_mark_inode_in_use > __cachefiles_mark_inode_in_use > can_use = false > if (!(inode->i_flags & S_KERNEL_FILE)) > can_use = true > return false > return false > // Returns an error but doesn't put dentry > > After that the following WARNING will be triggered when the backend folder > is umounted: > > ================================================================== > BUG: Dentry 000000008ad87947{i=7a,n=Dx_1_1.img} still in use (1) [unmount of ext4 sda] > WARNING: CPU: 4 PID: 359261 at fs/dcache.c:1767 umount_check+0x5d/0x70 > CPU: 4 PID: 359261 Comm: umount Not tainted 6.6.0-dirty #25 > RIP: 0010:umount_check+0x5d/0x70 > Call Trace: > <TASK> > d_walk+0xda/0x2b0 > do_one_tree+0x20/0x40 > shrink_dcache_for_umount+0x2c/0x90 > generic_shutdown_super+0x20/0x160 > kill_block_super+0x1a/0x40 > ext4_kill_sb+0x22/0x40 > deactivate_locked_super+0x35/0x80 > cleanup_mnt+0x104/0x160 > ================================================================== > > Whether cachefiles_open_file() returns true or false, the reference count > obtained by lookup_positive_unlocked() in cachefiles_look_up_object() > should be released. > > Therefore release that reference count in cachefiles_look_up_object() to > fix the above issue and simplify the code. > > Fixes: 1f08c925e7a3 ("cachefiles: Implement backing file wrangling") > Cc: stable@kernel.org > Signed-off-by: Baokun Li <libaokun1@huawei.com> Acked-by: David Howells <dhowells@redhat.com>
On Thu, 29 Aug 2024 16:34:09 +0800, libaokun@huaweicloud.com wrote: > A dentry leak may be caused when a lookup cookie and a cull are concurrent: > > P1 | P2 > ----------------------------------------------------------- > cachefiles_lookup_cookie > cachefiles_look_up_object > lookup_one_positive_unlocked > // get dentry > cachefiles_cull > inode->i_flags |= S_KERNEL_FILE; > cachefiles_open_file > cachefiles_mark_inode_in_use > __cachefiles_mark_inode_in_use > can_use = false > if (!(inode->i_flags & S_KERNEL_FILE)) > can_use = true > return false > return false > // Returns an error but doesn't put dentry > > [...] Applied to the vfs.fixes branch of the vfs/vfs.git tree. Patches in the vfs.fixes branch should appear in linux-next soon. Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it. It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated. Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch. tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: vfs.fixes [1/1] cachefiles: fix dentry leak in cachefiles_open_file() https://git.kernel.org/vfs/vfs/c/31075a6ed624
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c index f53977169db4..2b3f9935dbb4 100644 --- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -595,14 +595,12 @@ static bool cachefiles_open_file(struct cachefiles_object *object, * write and readdir but not lookup or open). */ touch_atime(&file->f_path); - dput(dentry); return true; check_failed: fscache_cookie_lookup_negative(object->cookie); cachefiles_unmark_inode_in_use(object, file); fput(file); - dput(dentry); if (ret == -ESTALE) return cachefiles_create_file(object); return false; @@ -611,7 +609,6 @@ static bool cachefiles_open_file(struct cachefiles_object *object, fput(file); error: cachefiles_do_unmark_inode_in_use(object, d_inode(dentry)); - dput(dentry); return false; } @@ -654,7 +651,9 @@ bool cachefiles_look_up_object(struct cachefiles_object *object) goto new_file; } - if (!cachefiles_open_file(object, dentry)) + ret = cachefiles_open_file(object, dentry); + dput(dentry); + if (!ret) return false; _leave(" = t [%lu]", file_inode(object->file)->i_ino);