From 9c2b9d30e28559a78c9e431cdd7f2c6bf5a9ee67 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 29 Sep 2014 12:12:01 +0200 Subject: [PATCH] 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: Oleg Nesterov Reported-by: Oleg Nesterov Reported-by: Sylvain 'ythier' Hitier Signed-off-by: Peter Zijlstra (Intel) Cc: Aaron Tomlin Cc: Andrew Morton Cc: Arnaldo Carvalho de Melo Cc: Daeseok Youn Cc: David Rientjes Cc: Kees Cook Cc: Linus Torvalds Cc: Paul Mackerras Cc: Rik van Riel Cc: Vladimir Davydov Cc: Link: http://lkml.kernel.org/r/20140929101201.GE5430@worktop Signed-off-by: Ingo Molnar --- kernel/events/core.c | 4 +++- kernel/fork.c | 5 +++-- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index afdd9e1d7144..658f232af04c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7956,8 +7956,10 @@ 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; diff --git a/kernel/fork.c b/kernel/fork.c index 0cf9cdb6e491..a91e47d86de2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -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: -- 2.20.1