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Commit 9c2b9d30 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf: Fix perf bug in fork() 



Oleg noticed that a cleanup by Sylvain actually uncovered a bug; by
calling perf_event_free_task() when failing sched_fork() we will not yet
have done the memset() on ->perf_event_ctxp[] and will therefore try and
'free' the inherited contexts, which are still in use by the parent
process.

This is bad and might explain some outstanding fuzzer failures ...

Suggested-by: default avatarOleg Nesterov <oleg@redhat.com>
Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
Reported-by: default avatarSylvain 'ythier' Hitier <sylvain.hitier@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Daeseok Youn <daeseok.youn@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20140929101201.GE5430@worktop


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 211de6eb

kernel/events/core.c

+3 −1
Original line number Diff line number Diff line
@@ -7956,9 +7956,11 @@ int perf_event_init_task(struct task_struct *child) 


	for_each_task_context_nr(ctxn) {

		ret = perf_event_init_context(child, ctxn);

		if (ret)

		if (ret) {

			perf_event_free_task(child);

			return ret;

		}

	}



	return 0;

}

kernel/fork.c

+3 −2
Original line number Diff line number Diff line
@@ -1360,7 +1360,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
		goto bad_fork_cleanup_policy;

	retval = audit_alloc(p);

	if (retval)

		goto bad_fork_cleanup_policy;

		goto bad_fork_cleanup_perf;

	/* copy all the process information */

	shm_init_task(p);

	retval = copy_semundo(clone_flags, p);
@@ -1566,8 +1566,9 @@ bad_fork_cleanup_semundo: 
	exit_sem(p);

bad_fork_cleanup_audit:

	audit_free(p);

bad_fork_cleanup_policy:

bad_fork_cleanup_perf:

	perf_event_free_task(p);

bad_fork_cleanup_policy:

#ifdef CONFIG_NUMA

	mpol_put(p->mempolicy);

bad_fork_cleanup_threadgroup_lock: