[PATCH] md/raid5: fix possible NULL pointer dereference in debug routine

When I ran dynamic debug, I encountered a NULL pointer dereference
bug in add_stripe_bio(). Prior to second call to pr_debug(), @bi
was reused in order to check whether the request is partial write
or not, and it could lead to set @bi to NULL.

Since we save original @bi pointer into local variable 'bip', use
it instead of NULL-able @bi.

Also changed confusing 'bh' to 'bi' in the first message.

Signed-off-by: Namhyung Kim
---
drivers/md/raid5.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 82c07fb38961..c814a6075c79 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2139,7 +2139,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
raid5_conf_t *conf = sh->raid_conf;
int firstwrite=0;

- pr_debug("adding bh b#%llu to stripe s#%llu\n",
+ pr_debug("adding bi b#%llu to stripe s#%llu\n",
(unsigned long long)bi->bi_sector,
(unsigned long long)sh->sector);

@@ -2181,7 +2181,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
spin_unlock_irq(&conf->device_lock);

pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
- (unsigned long long)bi->bi_sector,
+ (unsigned long long)(*bip)->bi_sector,
(unsigned long long)sh->sector, dd_idx);

if (conf->mddev->bitmap && firstwrite) {
--
1.7.5.2

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Re: [PATCH] md/raid5: fix possible NULL pointer dereference indebug routine

On Fri, 24 Jun 2011 14:04:00 +0900 Namhyung Kim wrote:

> When I ran dynamic debug, I encountered a NULL pointer dereference
> bug in add_stripe_bio(). Prior to second call to pr_debug(), @bi
> was reused in order to check whether the request is partial write
> or not, and it could lead to set @bi to NULL.
>
> Since we save original @bi pointer into local variable 'bip', use
> it instead of NULL-able @bi.
>
> Also changed confusing 'bh' to 'bi' in the first message.
>
> Signed-off-by: Namhyung Kim
> ---
> drivers/md/raid5.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 82c07fb38961..c814a6075c79 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -2139,7 +2139,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
> raid5_conf_t *conf = sh->raid_conf;
> int firstwrite=0;
>
> - pr_debug("adding bh b#%llu to stripe s#%llu\n",
> + pr_debug("adding bi b#%llu to stripe s#%llu\n",
> (unsigned long long)bi->bi_sector,
> (unsigned long long)sh->sector);
>
> @@ -2181,7 +2181,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
> spin_unlock_irq(&conf->device_lock);
>
> pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
> - (unsigned long long)bi->bi_sector,
> + (unsigned long long)(*bip)->bi_sector,
> (unsigned long long)sh->sector, dd_idx);
>
> if (conf->mddev->bitmap && firstwrite) {


Applied, thanks.

NeilBrown
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