[PATCH] blk_init_allocated_queue() set q->fq as NULL in the fail case

[PATCH] blk_init_allocated_queue() set q->fq as NULL in the fail case

[xiao jin]

We find the memory use-after-free issue in __blk_drain_queue()
on the kernel 4.14. After read the latest kernel 4.18-rc6 we
think it has the same problem.

Memory is allocated for q->fq in the blk_init_allocated_queue().
If the elevator init function called with error return, it will
run into the fail case to free the q->fq.

Then the __blk_drain_queue() uses the same memory after the free
of the q->fq, it will lead to the unpredictable event.

The patch is to set q->fq as NULL in the fail case of
blk_init_allocated_queue().

Signed-off-by: xiao jin <jin.xiao@intel.com>
---
 block/blk-core.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-core.c b/block/blk-core.c
index b888175..52635e2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1072,6 +1072,7 @@ int blk_init_allocated_queue(struct request_queue *q)
 		q->exit_rq_fn(q, q->fq->flush_rq);
 out_free_flush_queue:
 	blk_free_flush_queue(q->fq);
+	q->fq = NULL;
 	return -ENOMEM;
 }
 EXPORT_SYMBOL(blk_init_allocated_queue);
-- 
1.7.9.5

Re: [PATCH] blk_init_allocated_queue() set q->fq as NULL in the fail case

[Ming Lei]

On Mon, Jul 30, 2018 at 10:03 AM, xiao jin <jin.xiao@intel.com> wrote:
> We find the memory use-after-free issue in __blk_drain_queue()
> on the kernel 4.14. After read the latest kernel 4.18-rc6 we
> think it has the same problem.
>
> Memory is allocated for q->fq in the blk_init_allocated_queue().
> If the elevator init function called with error return, it will
> run into the fail case to free the q->fq.
>
> Then the __blk_drain_queue() uses the same memory after the free
> of the q->fq, it will lead to the unpredictable event.
>
> The patch is to set q->fq as NULL in the fail case of
> blk_init_allocated_queue().
>
> Signed-off-by: xiao jin <jin.xiao@intel.com>
> ---
>  block/blk-core.c |    1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index b888175..52635e2 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1072,6 +1072,7 @@ int blk_init_allocated_queue(struct request_queue *q)
>                 q->exit_rq_fn(q, q->fq->flush_rq);
>  out_free_flush_queue:
>         blk_free_flush_queue(q->fq);
> +       q->fq = NULL;
>         return -ENOMEM;
>  }
>  EXPORT_SYMBOL(blk_init_allocated_queue);
> --
> 1.7.9.5
>

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming Lei

Re: [PATCH] blk_init_allocated_queue() set q->fq as NULL in the fail case

[Bart Van Assche]

On Mon, 2018-07-30 at 10:03 +0800, xiao jin wrote:
> We find the memory use-after-free issue in __blk_drain_queue()
> on the kernel 4.14. After read the latest kernel 4.18-rc6 we
> think it has the same problem.
> 
> Memory is allocated for q->fq in the blk_init_allocated_queue().
> If the elevator init function called with error return, it will
> run into the fail case to free the q->fq.
> 
> Then the __blk_drain_queue() uses the same memory after the free
> of the q->fq, it will lead to the unpredictable event.
> 
> The patch is to set q->fq as NULL in the fail case of
> blk_init_allocated_queue().

Please add "Fixes:" and "Cc: stable" tags to this patch.

Thanks,

Bart.