2009-09-11 22:35:27

by Carsten Emde

Subject: [PATCH] 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 <[email protected]>

--- 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);

2009-09-11 22:15:05

by Steven Rostedt

Subject: Re: [PATCH] Prevent NULL pointer dereference in ftrace_raw_event_block_bio_bounce

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 <[email protected]>

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);
>

2009-09-13 15:02:23

by Carsten Emde

Subject: [tip:tracing/core] tracing: prevent NULL pointer dereference in ftrace_raw_event_block_bio_bounce

Commit-ID: fe63b94a430c0c8058de317f0a8ce921c69dbee4
Gitweb: http://git.kernel.org/tip/fe63b94a430c0c8058de317f0a8ce921c69dbee4
Author: Carsten Emde <[email protected]>
AuthorDate: Sat, 12 Sep 2009 00:05:37 +0200
Committer: Steven Rostedt <[email protected]>
CommitDate: Sat, 12 Sep 2009 21:31:19 -0400

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 <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>


---
include/trace/events/block.h | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/include/trace/events/block.h b/include/trace/events/block.h
index 9a74b46..d86af94 100644
--- a/include/trace/events/block.h
+++ b/include/trace/events/block.h
@@ -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);