6.11-stable review patch. If anyone has any objections, please let me know.
------------------
From: Baokun Li <libaokun1@xxxxxxxxxx>
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@xxxxxxxxxx
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240829083409.3788142-1-libaokun@xxxxxxxxxxxxxxx
Acked-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/cachefiles/namei.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -595,14 +595,12 @@ 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;
@@ -611,7 +609,6 @@ error_fput:
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 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);
