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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>
hifive-unleashed-5.1
Carsten Emde 2009-09-12 00:05:37 +02:00 committed by Steven Rostedt
parent 689fd8b65d
commit fe63b94a43
1 changed files with 3 additions and 1 deletions
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4
include/trace/events/block.h
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@ -171,6 +171,7 @@ TRACE_EVENT(block_rq_complete,
(unsigned long long)__entry->sector,
__entry->nr_sector, __entry->errors)
);
TRACE_EVENT(block_bio_bounce,
TP_PROTO(struct request_queue *q, struct bio *bio),
@ -186,7 +187,8 @@ TRACE_EVENT(block_bio_bounce,
),
TP_fast_assign(
__entry->dev = bio->bi_bdev->bd_dev;
__entry->dev = bio->bi_bdev ?
bio->bi_bdev->bd_dev : 0;
__entry->sector = bio->bi_sector;
__entry->nr_sector = bio->bi_size >> 9;
blk_fill_rwbs(__entry->rwbs, bio->bi_rw, bio->bi_size);