On Thu, Aug 12, 2021 at 8:46 PM lwt105 <[email protected]> wrote:
>
> In line 2867, "raid5_release_stripe(sh);" drops the reference to sh and
> may cause sh to be released. However, sh is subsequently used in lines
> 2869 "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.
>
> Signed-off-by: lwt105 <[email protected]>
The fix looks reasonable. I guess lwt105 is not a real name. Please update
the diff with your real name.
Thanks,
Song
> ---
> 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 b8436e4930ed..16ed44646419 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -2864,10 +2864,10 @@ 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
>
On 8/14/21 12:16 AM, Song Liu wrote:
> On Thu, Aug 12, 2021 at 8:46 PM lwt105<[email protected]> wrote:
>> In line 2867, "raid5_release_stripe(sh);" drops the reference to sh and
>> may cause sh to be released. However, sh is subsequently used in lines
>> 2869 "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.
>>
>> Signed-off-by: lwt105<[email protected]>
> The fix looks reasonable.
I am not sure this is needed unless there is real calltrace to prove it.
Because raid5_release_stripe
doesn't mean it will release the sh's memory, pls see the comment
before clear_batch_ready in
handle_stripe, and the path handle_stripe -> handle_stripe_clean_event
-> break_stripe_batch_list.
Thanks,
Guoqing