David Howells e6bc06faf6 cachefiles: Fix an assertion failure when trying to update a failed object ... If cachefiles gets an error other then ENOENT when trying to look up an object in the cache (in this case, EACCES), the object state machine will eventually transition to the DROP_OBJECT state. This state invokes fscache_drop_object() which tries to sync the auxiliary data with the cache (this is done lazily since commit 402cb8dda9) on an incomplete cache object struct. The problem comes when cachefiles_update_object_xattr() is called to rewrite the xattr holding the data. There's an assertion there that the cache object points to a dentry as we're going to update its xattr. The assertion trips, however, as dentry didn't get set. Fix the problem by skipping the update in cachefiles if the object doesn't refer to a dentry. A better way to do it could be to skip the update from the DROP_OBJECT state handler in fscache, but that might deny the cache the opportunity to update intermediate state. If this error occurs, the kernel log includes lines that look like the following: CacheFiles: Lookup failed error -13 CacheFiles: CacheFiles: Assertion failed ------------[ cut here ]------------ kernel BUG at fs/cachefiles/xattr.c:138! ... Workqueue: fscache_object fscache_object_work_func [fscache] RIP: 0010:cachefiles_update_object_xattr.cold.4+0x18/0x1a [cachefiles] ... Call Trace: cachefiles_update_object+0xdd/0x1c0 [cachefiles] fscache_update_aux_data+0x23/0x30 [fscache] fscache_drop_object+0x18e/0x1c0 [fscache] fscache_object_work_func+0x74/0x2b0 [fscache] process_one_work+0x18d/0x340 worker_thread+0x2e/0x390 ? pwq_unbound_release_workfn+0xd0/0xd0 kthread+0x112/0x130 ? kthread_bind+0x30/0x30 ret_from_fork+0x35/0x40 Note that there are actually two issues here: (1) EACCES happened on a cache object and (2) an oops occurred. I think that the second is a consequence of the first (it certainly looks like it ought to be). This patch only deals with the second. Fixes: 402cb8dda9 ("fscache: Attach the index key and aux data to the cookie") Reported-by: Zhibin Li <zhibli@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com>		2018-11-28 13:19:20 +00:00
..
Kconfig	CacheFiles: A cache that backs onto a mounted filesystem	2009-04-03 16:42:41 +01:00
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
bind.c	fscache: Fix reference overput in fscache_attach_object() error handling	2018-07-25 14:49:00 +01:00
daemon.c	vfs: do bulk POLL* -> EPOLL* replacement	2018-02-11 14:34:03 -08:00
interface.c	fscache: Pass object size in rather than calling back for it	2018-04-06 14:05:14 +01:00
internal.h	fscache: Add tracepoints	2018-04-04 13:41:27 +01:00
key.c	CacheFiles: Downgrade the requirements passed to the allocator	2012-12-20 21:58:25 +00:00
main.c	fscache: Add tracepoints	2018-04-04 13:41:27 +01:00
namei.c	cachefiles: fix the race between cachefiles_bury_object() and rmdir(2)	2018-10-18 11:32:21 +02:00
proc.c	proc: introduce proc_create_seq{,_data}	2018-05-16 07:23:35 +02:00
rdwr.c	cachefiles: Fix refcounting bug in backing-file read monitoring	2018-07-25 14:49:00 +01:00
security.c	VFS: fs/cachefiles: d_backing_inode() annotations	2015-04-15 15:06:59 -04:00
xattr.c	cachefiles: Fix an assertion failure when trying to update a failed object	2018-11-28 13:19:20 +00:00