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SubjectRe: [PATCH] Prevent NULL pointer dereference in ftrace_raw_event_block_bio_bounce
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On Sat, 2009-09-12 at 00:05 +0200, Carsten Emde wrote:
> 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>

Thanks Carsten!

I'll apply it and push it off to Ingo.

-- Steve

>
> --- a/include/trace/events/block.h 2009-09-11 21:20:56.000000000 +0200
> +++ b/include/trace/events/block.h 2009-09-11 22:01:52.000000000 +0200
> @@ -186,7 +186,8 @@
> ),
>
> 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);
>



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