On 2020-02-06 06:28, Jan Kara wrote: > KASAN is reporting that __blk_add_trace() has a use-after-free issue > when accessing q->blk_trace. Indeed the switching of block tracing (and > thus eventual freeing of q->blk_trace) is completely unsynchronized with > the currently running tracing and thus it can happen that the blk_trace > structure is being freed just while __blk_add_trace() works on it. > Protect accesses to q->blk_trace by RCU during tracing and make sure we > wait for the end of RCU grace period when shutting down tracing. Luckily > that is rare enough event that we can afford that. Note that postponing > the freeing of blk_trace to an RCU callback should better be avoided as > it could have unexpected user visible side-effects as debugfs files > would be still existing for a short while block tracing has been shut > down. Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
