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tracing: Fix crash from reading trace_pipe with sendfile

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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 <rabin.vincent@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2016-03-18 15:46:48 -04:00 committed by Greg Kroah-Hartman
parent aa60f652ee
commit aab3ba82f8
1 changed files with 4 additions and 1 deletions
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5
kernel/trace/trace.c
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@ -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;