From: Steven Rostedt (Red Hat) Date: Fri, 18 Mar 2016 19:46:48 +0000 (-0400) Subject: tracing: Fix crash from reading trace_pipe with sendfile X-Git-Tag: firefly_0821_release~176^2~4^2~50^2~46 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=aab3ba82f8445abe99f33e743e7316d0d55fee7b;p=firefly-linux-kernel-4.4.55.git tracing: Fix crash from reading trace_pipe with sendfile commit a29054d9478d0435ab01b7544da4f674ab13f533 upstream. If tracing contains data and the trace_pipe file is read with sendfile(), then it can trigger a NULL pointer dereference and various BUG_ON within the VM code. There's a patch to fix this in the splice_to_pipe() code, but it's also a good idea to not let that happen from trace_pipe either. Link: http://lkml.kernel.org/r/1457641146-9068-1-git-send-email-rabin@rab.in Reported-by: Rabin Vincent Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index d9293402ee68..8305cbb2d5a2 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4949,7 +4949,10 @@ static ssize_t tracing_splice_read_pipe(struct file *filp, spd.nr_pages = i; - ret = splice_to_pipe(pipe, &spd); + if (i) + ret = splice_to_pipe(pipe, &spd); + else + ret = 0; out: splice_shrink_spd(&spd); return ret;