[PATCH RESEND] cachefiles: fix memory leak in cachefiles_add_cache()

[David Howells]

Hi Christian,

Could you take this through your VFS tree please?

> The following memory leak was reported after unbinding /dev/cachefiles:
> 
> ==================================================================
> unreferenced object 0xffff9b674176e3c0 (size 192):
>   comm "cachefilesd2", pid 680, jiffies 4294881224
>   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 ea38a44b):
>     [<ffffffff8eb8a1a5>] kmem_cache_alloc+0x2d5/0x370
>     [<ffffffff8e917f86>] prepare_creds+0x26/0x2e0
>     [<ffffffffc002eeef>] cachefiles_determine_cache_security+0x1f/0x120
>     [<ffffffffc00243ec>] cachefiles_add_cache+0x13c/0x3a0
>     [<ffffffffc0025216>] cachefiles_daemon_write+0x146/0x1c0
>     [<ffffffff8ebc4a3b>] vfs_write+0xcb/0x520
>     [<ffffffff8ebc5069>] ksys_write+0x69/0xf0
>     [<ffffffff8f6d4662>] do_syscall_64+0x72/0x140
>     [<ffffffff8f8000aa>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
> ==================================================================
> 
> Put the reference count of cache_cred in cachefiles_daemon_unbind() to
> fix the problem. And also put cache_cred in cachefiles_add_cache() error
> branch to avoid memory leaks.
> 
> Fixes: 9ae326a69004 ("CacheFiles: A cache that backs onto a mounted filesystem")
> CC: stable at vger.kernel.org
> Signed-off-by: Baokun Li <libaokun1 at huawei.com>

and add:

Reviewed-by: Jingbo Xu <jefflexu at linux.alibaba.com>
Reviewed-by: Jeff Layton <jlayton at kernel.org>
Acked-by: David Howells <dhowells at redhat.com>