From 7eca210375dcc029ad69c0cf48d2bf7a71f0121d Mon Sep 17 00:00:00 2001 From: Arianna Avanzini Date: Tue, 9 Dec 2014 14:57:45 -0700 Subject: [PATCH] blktrace: don't let the sysfs interface remove trace from running list Currently, blktrace can be started/stopped via its ioctl-based interface (used by the userspace blktrace tool) or via its ftrace interface. The function blk_trace_remove_queue(), called each time an "enable" tunable of the ftrace interface transitions to zero, removes the trace from the running list, even if no function from the sysfs interface adds it to such a list. This leads to a null pointer dereference. This commit changes the blk_trace_remove_queue() function so that it does not remove the blk_trace from the running list. v2: - Now the patch removes the invocation of list_del() instead of adding an useless if branch, as suggested by Namhyung Kim. Signed-off-by: Arianna Avanzini Signed-off-by: Jens Axboe --- kernel/trace/blktrace.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index c1bd4ada2a04..bd05fd2d5d2b 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1493,9 +1493,6 @@ static int blk_trace_remove_queue(struct request_queue *q) if (atomic_dec_and_test(&blk_probes_ref)) blk_unregister_tracepoints(); - spin_lock_irq(&running_trace_lock); - list_del(&bt->running_list); - spin_unlock_irq(&running_trace_lock); blk_trace_free(bt); return 0; } -- 2.30.2