6.1-stable review patch. If anyone has any objections, please let me know.
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From: Baokun Li libaokun1@huawei.com
commit da6ef2dffe6056aad3435e6cf7c6471c2a62187c upstream.
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 Link: https://lore.kernel.org/r/20240829083409.3788142-1-libaokun@huaweicloud.com Acked-by: David Howells dhowells@redhat.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/cachefiles/namei.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -593,14 +593,12 @@ static bool cachefiles_open_file(struct * 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; @@ -609,7 +607,6 @@ error_fput: fput(file); error: cachefiles_do_unmark_inode_in_use(object, d_inode(dentry)); - dput(dentry); return false; }
@@ -652,7 +649,9 @@ bool cachefiles_look_up_object(struct ca 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);