From 6e9bfdcf0a3b1c8126878c21adcfc343f89d4a6a Mon Sep 17 00:00:00 2001 From: Dave Wysochanski Date: Fri, 1 Oct 2021 15:37:31 +0100 Subject: [PATCH] cachefiles: Fix oops in trace_cachefiles_mark_buried due to NULL object 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 ("fscache: Add a cookie debug ID and use that in traces"). This fixes the following oops: FS-Cache: Cache "mycache" added (type cachefiles) CacheFiles: File cache on vdc registered ... Workqueue: fscache_object fscache_object_work_func [fscache] RIP: 0010:trace_event_raw_event_cachefiles_mark_buried+0x4e/0xa0 [cachefiles] .... Call Trace: cachefiles_mark_object_buried+0xa5/0xb0 [cachefiles] cachefiles_bury_object+0x270/0x430 [cachefiles] cachefiles_walk_to_object+0x195/0x9c0 [cachefiles] cachefiles_lookup_object+0x5a/0xc0 [cachefiles] fscache_look_up_object+0xd7/0x160 [fscache] fscache_object_work_func+0xb2/0x340 [fscache] process_one_work+0x1f1/0x390 worker_thread+0x53/0x3e0 kthread+0x127/0x150 Fixes: 2908f5e101e3 ("fscache: Add a cookie debug ID and use that in traces") Signed-off-by: Dave Wysochanski Signed-off-by: David Howells cc: linux-cachefs@redhat.com Signed-off-by: Linus Torvalds --- 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 @@ TRACE_EVENT(cachefiles_mark_buried, ), TP_fast_assign( - __entry->obj = obj->fscache.debug_id; + __entry->obj = obj ? obj->fscache.debug_id : UINT_MAX; __entry->de = de; __entry->why = why; ),