From ebf905fc7a6e7c99c53b5afc888d8f950da90aff Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 29 May 2014 19:00:24 +0200 Subject: [PATCH] perf: Fix use after free in perf_remove_from_context() While that mutex should guard the elements, it doesn't guard against the use-after-free that's from list_for_each_entry_rcu(). __perf_event_exit_task() can actually free the event. And because list addition/deletion is guarded by both ctx->mutex and ctx->lock, holding ctx->mutex is sufficient for reading the list, so we don't actually need the rcu list iteration. Fixes: 3a497f48637e ("perf: Simplify perf_event_exit_task_context()") Reported-by: Sasha Levin Tested-by: Sasha Levin Signed-off-by: Peter Zijlstra Cc: Dave Jones Cc: acme@ghostprotocols.net Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140529170024.GA2315@laptop.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index ed50b0943213..a62d142ad498 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7431,7 +7431,7 @@ __perf_event_exit_task(struct perf_event *child_event, static void perf_event_exit_task_context(struct task_struct *child, int ctxn) { - struct perf_event *child_event; + struct perf_event *child_event, *next; struct perf_event_context *child_ctx; unsigned long flags; @@ -7485,7 +7485,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) */ mutex_lock(&child_ctx->mutex); - list_for_each_entry_rcu(child_event, &child_ctx->event_list, event_entry) + list_for_each_entry_safe(child_event, next, &child_ctx->event_list, event_entry) __perf_event_exit_task(child_event, child_ctx, child); mutex_unlock(&child_ctx->mutex);