2022-07-28 03:42:41

by Wentao_Liang

Subject: [PATCH] drivers:md:fix a potential use-after-free bug

In line 2884, "raid5_release_stripe(sh);" drops the reference to sh and
may cause sh to be released. However, sh is subsequently used in lines
2886 "if (sh->batch_head && sh != sh->batch_head)". This may result in an
use-after-free bug.

It can be fixed by moving "raid5_release_stripe(sh);" to the bottom of
the function.

The bug has been confirmed by Song on 2021-08-14. Now, I resend this
patch with my real name. I hope the patch can be updated in a near
future.

Signed-off-by: Wentao_Liang <[email protected]>
---
drivers/md/raid5.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5d09256d7f81..93fcbeac5096 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2881,10 +2881,10 @@ static void raid5_end_write_request(struct bio *bi)
if (!test_and_clear_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags))
clear_bit(R5_LOCKED, &sh->dev[i].flags);
set_bit(STRIPE_HANDLE, &sh->state);
- raid5_release_stripe(sh);

if (sh->batch_head && sh != sh->batch_head)
raid5_release_stripe(sh->batch_head);
+ raid5_release_stripe(sh);
}

static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)
--
2.25.1

2022-07-28 06:20:40

by Song Liu

Subject: Re: [PATCH] drivers:md:fix a potential use-after-free bug

On Wed, Jul 27, 2022 at 8:40 PM Wentao_Liang <[email protected]> wrote:
>
> In line 2884, "raid5_release_stripe(sh);" drops the reference to sh and
> may cause sh to be released. However, sh is subsequently used in lines
> 2886 "if (sh->batch_head && sh != sh->batch_head)". This may result in an
> use-after-free bug.
>
> It can be fixed by moving "raid5_release_stripe(sh);" to the bottom of
> the function.
>
> The bug has been confirmed by Song on 2021-08-14. Now, I resend this
> patch with my real name. I hope the patch can be updated in a near
> future.

I removed this paragraph while applying the patch, as it doesn't belong to
the commit log. In the future you can put it after a "---", so it will
be dropped
automatically by git-am. In other words, use something like:

========================================
...
Signed-off-by: Wentao_Liang <[email protected]>
---
The bug has been confirmed by Song on 2021-08-14. Now, I resend this
patch with my real name. I hope the patch can be updated in a near
future. (This will be dropped.)
---
drivers/md/raid5.c | 2 +-
...
======================================
>
> Signed-off-by: Wentao_Liang <[email protected]>

Applied to md-next. Thanks for the fix.


> ---
> drivers/md/raid5.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 5d09256d7f81..93fcbeac5096 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -2881,10 +2881,10 @@ static void raid5_end_write_request(struct bio *bi)
> if (!test_and_clear_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags))
> clear_bit(R5_LOCKED, &sh->dev[i].flags);
> set_bit(STRIPE_HANDLE, &sh->state);
> - raid5_release_stripe(sh);
>
> if (sh->batch_head && sh != sh->batch_head)
> raid5_release_stripe(sh->batch_head);
> + raid5_release_stripe(sh);
> }
>
> static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)
> --
> 2.25.1
>