From 00496fe5e09e8c8bb115540e7e3470553cd07a5c Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Fri, 1 Nov 2019 17:12:48 +0200 Subject: [PATCH] perf/aux: Fix the aux_output group inheritance fix Commit f733c6b508bc ("perf/core: Fix inheritance of aux_output groups") adds a NULL pointer dereference in case inherit_group() races with perf_release(), which causes the below crash: > BUG: kernel NULL pointer dereference, address: 000000000000010b > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 3b203b067 P4D 3b203b067 PUD 3b2040067 PMD 0 > Oops: 0000 [#1] SMP KASAN > CPU: 0 PID: 315 Comm: exclusive-group Tainted: G B 5.4.0-rc3-00181-g72e1839403cb-dirty #878 > RIP: 0010:perf_get_aux_event+0x86/0x270 > Call Trace: > ? __perf_read_group_add+0x3b0/0x3b0 > ? __kasan_check_write+0x14/0x20 > ? __perf_event_init_context+0x154/0x170 > inherit_task_group.isra.0.part.0+0x14b/0x170 > perf_event_init_task+0x296/0x4b0 Fix this by skipping over events that are getting closed, in the inheritance path. Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: David Ahern Cc: Jiri Olsa Cc: Linus Torvalds Cc: Mark Rutland Cc: Namhyung Kim Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Fixes: f733c6b508bc ("perf/core: Fix inheritance of aux_output groups") Link: https://lkml.kernel.org/r/20191101151248.47327-1-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar --- kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 022a34b66e60..b752bd3aa03b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11899,7 +11899,7 @@ static int inherit_group(struct perf_event *parent_event, if (IS_ERR(child_ctr)) return PTR_ERR(child_ctr); - if (sub->aux_event == parent_event && + if (sub->aux_event == parent_event && child_ctr && !perf_get_aux_event(child_ctr, leader)) return -EINVAL; }