Dave Wysochanski 37f0b459c9 fscache: Fix oops due to race with cookie_lru and use_cookie ... [ Upstream commit b5b52de321 ] If a cookie expires from the LRU and the LRU_DISCARD flag is set, but the state machine has not run yet, it's possible another thread can call fscache_use_cookie and begin to use it. When the cookie_worker finally runs, it will see the LRU_DISCARD flag set, transition the cookie->state to LRU_DISCARDING, which will then withdraw the cookie. Once the cookie is withdrawn the object is removed the below oops will occur because the object associated with the cookie is now NULL. Fix the oops by clearing the LRU_DISCARD bit if another thread uses the cookie before the cookie_worker runs. BUG: kernel NULL pointer dereference, address: 0000000000000008 ... CPU: 31 PID: 44773 Comm: kworker/u130:1 Tainted: G E 6.0.0-5.dneg.x86_64 #1 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022 Workqueue: events_unbound netfs_rreq_write_to_cache_work [netfs] RIP: 0010:cachefiles_prepare_write+0x28/0x90 [cachefiles] ... Call Trace: netfs_rreq_write_to_cache_work+0x11c/0x320 [netfs] process_one_work+0x217/0x3e0 worker_thread+0x4a/0x3b0 kthread+0xd6/0x100 Fixes: 12bb21a29c ("fscache: Implement cookie user counting and resource pinning") Reported-by: Daire Byrne <daire.byrne@gmail.com> Signed-off-by: Dave Wysochanski <dwysocha@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Daire Byrne <daire@dneg.com> Link: https://lore.kernel.org/r/20221117115023.1350181-1-dwysocha@redhat.com/ # v1 Link: https://lore.kernel.org/r/20221117142915.1366990-1-dwysocha@redhat.com/ # v2 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-12-14 11:40:51 +01:00
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Kconfig	fscache: remove FSCACHE_OLD_API Kconfig option	2022-04-08 23:54:37 +01:00
Makefile	fscache: Provide a means to begin an operation	2022-01-07 09:22:19 +00:00
cache.c	fscache: Use wrapper fscache_set_cache_state() directly when relinquishing	2022-04-08 23:54:37 +01:00
cookie.c	fscache: Fix oops due to race with cookie_lru and use_cookie	2022-12-14 11:40:51 +01:00
internal.h	fscache: Move fscache_cookies_seq_ops specific code under CONFIG_PROC_FS	2022-04-08 23:54:37 +01:00
io.c	fscache: Remove the cookie parameter from fscache_clear_page_bits()	2022-04-08 23:54:37 +01:00
main.c	fscache: Implement cookie-level access helpers	2022-01-07 09:22:19 +00:00
proc.c	fscache: Implement cookie registration	2022-01-07 09:22:19 +00:00
stats.c	fscache, cachefiles: Display stat of culling events	2022-01-07 13:43:18 +00:00
volume.c	fscache: fix OOB Read in __fscache_acquire_volume	2022-12-02 17:43:08 +01:00