From: Carsten Emde <Carsten.Emde@osadl.org>
Date: Fri, 11 Sep 2009 22:05:37 +0000 (+0200)
Subject: tracing: prevent NULL pointer dereference in ftrace_raw_event_block_bio_bounce
X-Git-Tag: v2.6.32-rc1~654^2~21
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe63b94a430c0c8058de317f0a8ce921c69dbee4;p=pandora-kernel.git

tracing: prevent NULL pointer dereference in ftrace_raw_event_block_bio_bounce

Booting 2.6.31 and executing
   echo 1 >/sys/kernel/debug/tracing/events/enable
leads to
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<c032a583>] ftrace_raw_event_block_bio_bounce+0x4b/0xb9

Apparently,
   bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);
is called in block/blk-map.c:58 where bio->bi_bdev in set to NULL and
still is NULL when an attempt is made to evaluate bio->bi_bdev->bd_dev
in include/trace/events/block.h:189.

The tracepoint should ensure bio->bi_bdev is not dereferenced, if NULL.

Signed-off-by: Carsten Emde <C.Emde@osadl.org>
LKML-Reference: <4AAAC9B1.9060505@osadl.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

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