Commit a551844e authored Dec 19, 2022 by Peter Zijlstra

perf: Fix use-after-free in error path



The syscall error path has a use-after-free; put_pmu_ctx() will
reference ctx, therefore we must ensure ctx is destroyed after pmu_ctx
is.

Fixes: bd275681 ("perf: Rewrite core context handling")
Reported-by:  <syzbot+b8e8c01c8ade4fe6e48f@syzkaller.appspotmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Chengming Zhou <zhouchengming@bytedance.com>
Link: https://lkml.kernel.org/r/Y6B3xEgkbmFUCeni@hirez.programming.kicks-ass.net

parent 08245672

kernel/events/core.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -12671,7 +12671,8 @@ SYSCALL_DEFINE5(perf_event_open,
		return event_fd;

		err_context:
		/* event->pmu_ctx freed by free_event() */
		put_pmu_ctx(event->pmu_ctx);
		event->pmu_ctx = NULL; /* _free_event() */
		err_locked:
		mutex_unlock(&ctx->mutex);
		perf_unpin_context(ctx);
		@@ -12784,6 +12785,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,

		err_pmu_ctx:
		put_pmu_ctx(pmu_ctx);
		event->pmu_ctx = NULL; /* _free_event() */
		err_unlock:
		mutex_unlock(&ctx->mutex);
		perf_unpin_context(ctx);