Amir Goldstein <amir73il@xxxxxxxxx> writes:
> On Thu, Nov 7, 2024 at 1:57 AM Vinicius Costa Gomes
> <vinicius.gomes@xxxxxxxxx> wrote:
[...]
>
> Vinicius,
>
> While testing fanotify with LTP tests (some are using overlayfs),
> kmemleak consistently reports the problems below.
>
> Can you see the bug, because I don't see it.
> Maybe it is a false positive...
Hm, if the leak wasn't there before and we didn't touch anything related to
prepare_creds(), I think that points to the leak being real.
But I see your point, still not seeing it.
This code should be equivalent to the code we have now (just boot
tested):
----
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 136a2c7fb9e5..7ebc2fd3097a 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -576,8 +576,7 @@ static int ovl_setup_cred_for_create(struct dentry *dentry, struct inode *inode,
* We must be called with creator creds already, otherwise we risk
* leaking creds.
*/
- WARN_ON_ONCE(override_creds(override_cred) != ovl_creds(dentry->d_sb));
- put_cred(override_cred);
+ WARN_ON_ONCE(override_creds_light(override_cred) != ovl_creds(dentry->d_sb));
return 0;
}
----
Does it change anything? (I wouldn't think so, just to try something)
>
> Christian, Miklos,
>
> Can you see a problem?
>
> Thanks,
> Amir.
>
>
> unreferenced object 0xffff888008ad8240 (size 192):
> comm "fanotify06", pid 1803, jiffies 4294890084
> hex dump (first 32 bytes):
> 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace (crc ee6a93ea):
> [<00000000ab4340a4>] __create_object+0x22/0x83
> [<0000000053dcaf3b>] kmem_cache_alloc_noprof+0x156/0x1e6
> [<00000000b4a08c1d>] prepare_creds+0x1d/0xf9
> [<00000000c55dfb6c>] ovl_setup_cred_for_create+0x27/0x93
> [<00000000f82af4ee>] ovl_create_or_link+0x73/0x1bd
> [<0000000040a439db>] ovl_create_object+0xda/0x11d
> [<00000000fbbadf17>] lookup_open.isra.0+0x3a0/0x3ff
> [<0000000007a2faf0>] open_last_lookups+0x160/0x223
> [<00000000e7d8243a>] path_openat+0x136/0x1b5
> [<0000000004e51585>] do_filp_open+0x57/0xb8
> [<0000000053871b92>] do_sys_openat2+0x6f/0xc0
> [<000000004d76b8b7>] do_sys_open+0x3f/0x60
> [<000000009b0be238>] do_syscall_64+0x96/0xf8
> [<000000006ff466ad>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
Cheers,
--
Vinicius
