In cachefiles_mark_object_buried, the dentry in question may
not have an owner, and thus our cachefiles_object pointer
may be NULL when calling the tracepoint, in which case we
will also not have a valid debug_id to print in the tracepoint.
Check for NULL object in the tracepoint and if so, just set
debug_id to MAX_UINT as was done in 2908f5e101e3.
This fixes the following oops:
[ 115.179145] FS-Cache: Cache "mycache" added (type cachefiles)
[ 115.182243] CacheFiles: File cache on vdc registered
[ 128.333709] t1_rsize_lt_rea (3600): drop_caches: 3
[ 128.401940] BUG: kernel NULL pointer dereference, address: 0000000000000010
[ 128.404908] #PF: supervisor read access in kernel mode
[ 128.407073] #PF: error_code(0x0000) - not-present page
[ 128.409738] PGD 0 P4D 0
[ 128.410960] Oops: 0000 [#1] SMP PTI
[ 128.411777] CPU: 1 PID: 178 Comm: kworker/u16:5 Kdump: loaded Not tainted 5.15.0-rc3 #61
[ 128.413182] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-4.fc34 04/01/2014
[ 128.414641] Workqueue: fscache_object fscache_object_work_func [fscache]
[ 128.415825] RIP: 0010:trace_event_raw_event_cachefiles_mark_buried+0x4e/0xa0 [cachefiles]
[ 128.417565] Code: 41 f6 c6 80 75 47 41 f6 c6 40 75 34 41 f7 c6 00 02 00 00 75 4b ba 20 00 00 00 48 89 ee 48 89 e7 e8 27 30 69 d2 48 85 c0 74 16 <41> 8b 55 10 4c 89 60 10 48 89 e7 89 58 18 89 50
08 e8 bc fd 67 d2
[ 128.420892] RSP: 0018:ffffaf8d4117fc08 EFLAGS: 00010282
[ 128.422032] RAX: ffff949d803b5834 RBX: 0000000000000000 RCX: 0000000000000088
[ 128.423348] RDX: ffff949d803b5834 RSI: ffff949d803b5830 RDI: ffff949d803b5830
[ 128.424506] RBP: ffff949d84041a50 R08: 0000001ea0136adf R09: ffffaf8d4117fb20
[ 128.425656] R10: ffff949d86c78f18 R11: 0000000000000000 R12: ffff949ded1f5780
[ 128.426932] R13: 0000000000000000 R14: 0000000000000403 R15: ffff949d887d8664
[ 128.428318] FS: 0000000000000000(0000) GS:ffff949ef7c40000(0000) knlGS:0000000000000000
[ 128.429761] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 128.430681] CR2: 0000000000000010 CR3: 0000000157404004 CR4: 0000000000770ee0
[ 128.431824] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 128.432953] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 128.434061] PKRU: 55555554
[ 128.434512] Call Trace:
[ 128.434944] cachefiles_mark_object_buried+0xa5/0xb0 [cachefiles]
[ 128.435903] cachefiles_bury_object+0x270/0x430 [cachefiles]
[ 128.436862] ? kfree+0xaa/0x3a0
[ 128.437396] ? vfs_getxattr+0x15a/0x180
[ 128.438038] cachefiles_walk_to_object+0x195/0x9c0 [cachefiles]
[ 128.438984] ? trace_event_buffer_commit+0x61/0x220
[ 128.439822] cachefiles_lookup_object+0x5a/0xc0 [cachefiles]
[ 128.440741] fscache_look_up_object+0xd7/0x160 [fscache]
[ 128.441615] fscache_object_work_func+0xb2/0x340 [fscache]
[ 128.442547] process_one_work+0x1f1/0x390
[ 128.443225] worker_thread+0x53/0x3e0
[ 128.443854] ? process_one_work+0x390/0x390
[ 128.444527] kthread+0x127/0x150
[ 128.445058] ? set_kthread_struct+0x40/0x40
[ 128.445726] ret_from_fork+0x22/0x30
Fixes: 2908f5e101e3 ("fscache: Add a cookie debug ID and use that in traces")
Signed-off-by: Dave Wysochanski <dwysocha@xxxxxxxxxx>
---
include/trace/events/cachefiles.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h
index 9a448fe9355d..695bfdbfdcad 100644
--- a/include/trace/events/cachefiles.h
+++ b/include/trace/events/cachefiles.h
@@ -305,7 +305,7 @@ enum cachefiles_obj_ref_trace {
),
TP_fast_assign(
- __entry->obj = obj->fscache.debug_id;
+ __entry->obj = obj ? obj->fscache.debug_id : UINT_MAX;
__entry->de = de;
__entry->why = why;
),
--
1.8.3.1
