2017-04-26 10:00:52

by Heloise

Subject: [PATCH] drbd:fix null pointer deref in _drbd_md_sync_page_io

The return value of bio_alloc_drbd can be NULL and is used without
validation, which may cause null-pointer dereference, fix it.

Signed-off-by: Heloise <[email protected]>
---
drivers/block/drbd/drbd_actlog.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 8d7bcfa..d6bb30e 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -151,6 +151,10 @@ static int _drbd_md_sync_page_io(struct drbd_device *device,
op_flags |= REQ_SYNC;

bio = bio_alloc_drbd(GFP_NOIO);
+ if (!bio) {
+ err = -ENOMEM;
+ return err;
+ }
bio->bi_bdev = bdev->md_bdev;
bio->bi_iter.bi_sector = sector;
err = -EIO;
--
2.1.0

2017-04-26 13:24:56

by Lars Ellenberg

Subject: Re: [PATCH] drbd:fix null pointer deref in _drbd_md_sync_page_io

On Wed, Apr 26, 2017 at 02:49:37AM -0700, Heloise wrote:
> The return value of bio_alloc_drbd can be NULL and is used without

No, apparently it cannot, because it is basically a mempool_alloc()
with GFP_NOIO, it may sleep, but it will loop "forever" and not return NULL.

So rather fix that nonsense in bio_alloc_drbd, see below:

Thanks,

Lars

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 92c60cb..9ffd940 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -150,15 +150,10 @@ static const struct block_device_operations drbd_ops = {

struct bio *bio_alloc_drbd(gfp_t gfp_mask)
{
- struct bio *bio;
-
if (!drbd_md_io_bio_set)
return bio_alloc(gfp_mask, 1);

- bio = bio_alloc_bioset(gfp_mask, 1, drbd_md_io_bio_set);
- if (!bio)
- return NULL;
- return bio;
+ return bio_alloc_bioset(gfp_mask, 1, drbd_md_io_bio_set);
}

#ifdef __CHECKER__


> validation, which may cause null-pointer dereference, fix it.
>
> Signed-off-by: Heloise <[email protected]>
> ---
> drivers/block/drbd/drbd_actlog.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
> index 8d7bcfa..d6bb30e 100644
> --- a/drivers/block/drbd/drbd_actlog.c
> +++ b/drivers/block/drbd/drbd_actlog.c
> @@ -151,6 +151,10 @@ static int _drbd_md_sync_page_io(struct drbd_device *device,
> op_flags |= REQ_SYNC;
>
> bio = bio_alloc_drbd(GFP_NOIO);
> + if (!bio) {
> + err = -ENOMEM;
> + return err;
> + }
> bio->bi_bdev = bdev->md_bdev;
> bio->bi_iter.bi_sector = sector;
> err = -EIO;
> --
> 2.1.0