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Groups > linux.kernel > #1446350 > unrolled thread

[PATCH] Fix NULL pointer dereference in bl_free_device().

Started byArtem Savkov <asavkov@redhat.com>
First post2016-07-19 13:40 +0200
Last post2016-07-19 17:30 +0200
Articles 7 — 4 participants

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  [PATCH] Fix NULL pointer dereference in bl_free_device(). Artem Savkov <asavkov@redhat.com> - 2016-07-19 13:40 +0200
    Re: [PATCH] Fix NULL pointer dereference in bl_free_device(). Anna Schumaker <Anna.Schumaker@netapp.com> - 2016-07-19 17:30 +0200
      [PATCH v2] Fix NULL pointer dereference in bl_free_device(). Artem Savkov <asavkov@redhat.com> - 2016-07-19 17:50 +0200
        Re: [PATCH v2] Fix NULL pointer dereference in bl_free_device(). Christoph Hellwig <hch@lst.de> - 2016-07-21 10:10 +0200
          [PATCH v3] Fix NULL pointer dereference in bl_free_device(). Artem Savkov <asavkov@redhat.com> - 2016-07-21 13:40 +0200
            Re: [PATCH v3] Fix NULL pointer dereference in bl_free_device(). "Benjamin Coddington" <bcodding@redhat.com> - 2016-07-21 14:30 +0200
    Re: [PATCH] Fix NULL pointer dereference in bl_free_device(). Anna Schumaker <Anna.Schumaker@netapp.com> - 2016-07-19 17:30 +0200

#1446350 — [PATCH] Fix NULL pointer dereference in bl_free_device().

FromArtem Savkov <asavkov@redhat.com>
Date2016-07-19 13:40 +0200
Subject[PATCH] Fix NULL pointer dereference in bl_free_device().
Message-ID<rWBxv-3r9-3@gated-at.bofh.it>
When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
blkdev_get_by_*() step we get an pnfs_block_dev struct that is
uninitialized except for bdev field which is set to whatever error
blkdev_get_by_*() returns.  bl_free_device() then tries to call
blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.

Fixing this by making sure bdev is not an error code in bl_free_device().

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
 fs/nfs/blocklayout/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
index 118252f..7db3af0 100644
--- a/fs/nfs/blocklayout/dev.c
+++ b/fs/nfs/blocklayout/dev.c
@@ -33,7 +33,7 @@ bl_free_device(struct pnfs_block_dev *dev)
 				pr_err("failed to unregister PR key.\n");
 		}
 
-		if (dev->bdev)
+		if (dev->bdev && !IS_ERR(dev->bdev))
 			blkdev_put(dev->bdev, FMODE_READ | FMODE_WRITE);
 	}
 }
-- 
2.5.5

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#1446541

FromAnna Schumaker <Anna.Schumaker@netapp.com>
Date2016-07-19 17:30 +0200
Message-ID<rWF85-5Ir-1@gated-at.bofh.it>
In reply to#1446350
Hi Artem,

On 07/19/2016 07:30 AM, Artem Savkov wrote:
> When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
> blkdev_get_by_*() step we get an pnfs_block_dev struct that is
> uninitialized except for bdev field which is set to whatever error
> blkdev_get_by_*() returns.  bl_free_device() then tries to call
> blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.
> 
> Fixing this by making sure bdev is not an error code in bl_free_device().
> 
> Signed-off-by: Artem Savkov <asavkov@redhat.com>
> ---
>  fs/nfs/blocklayout/dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
> index 118252f..7db3af0 100644
> --- a/fs/nfs/blocklayout/dev.c
> +++ b/fs/nfs/blocklayout/dev.c
> @@ -33,7 +33,7 @@ bl_free_device(struct pnfs_block_dev *dev)
>  				pr_err("failed to unregister PR key.\n");
>  		}
>  
> -		if (dev->bdev)
> +		if (dev->bdev && !IS_ERR(dev->bdev))

This looks pretty straightforward, but can you use IS_ERR_OR_NULL() instead?  It accomplishes the same check with slightly cleaner code :)

Thanks,
Anna

>  			blkdev_put(dev->bdev, FMODE_READ | FMODE_WRITE);
>  	}
>  }
>

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#1446561 — [PATCH v2] Fix NULL pointer dereference in bl_free_device().

FromArtem Savkov <asavkov@redhat.com>
Date2016-07-19 17:50 +0200
Subject[PATCH v2] Fix NULL pointer dereference in bl_free_device().
Message-ID<rWFrr-5Qf-15@gated-at.bofh.it>
In reply to#1446541
When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
blkdev_get_by_*() step we get an pnfs_block_dev struct that is
uninitialized except for bdev field which is set to whatever error
blkdev_get_by_*() returns.  bl_free_device() then tries to call
blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.

Fixing this by making sure bdev is not an error code in bl_free_device().

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
 fs/nfs/blocklayout/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
index 118252f..57cb800 100644
--- a/fs/nfs/blocklayout/dev.c
+++ b/fs/nfs/blocklayout/dev.c
@@ -33,7 +33,7 @@ bl_free_device(struct pnfs_block_dev *dev)
 				pr_err("failed to unregister PR key.\n");
 		}
 
-		if (dev->bdev)
+		if (!IS_ERR_OR_NULL(dev->bdev))
 			blkdev_put(dev->bdev, FMODE_READ | FMODE_WRITE);
 	}
 }
-- 
2.5.5

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#1447694 — Re: [PATCH v2] Fix NULL pointer dereference in bl_free_device().

FromChristoph Hellwig <hch@lst.de>
Date2016-07-21 10:10 +0200
SubjectRe: [PATCH v2] Fix NULL pointer dereference in bl_free_device().
Message-ID<rXhdn-4QE-9@gated-at.bofh.it>
In reply to#1446561
On Tue, Jul 19, 2016 at 05:39:04PM +0200, Artem Savkov wrote:
> When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
> blkdev_get_by_*() step we get an pnfs_block_dev struct that is
> uninitialized except for bdev field which is set to whatever error
> blkdev_get_by_*() returns.  bl_free_device() then tries to call
> blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.
> 
> Fixing this by making sure bdev is not an error code in bl_free_device().
> 
> Signed-off-by: Artem Savkov <asavkov@redhat.com>

I guess this is fine to be defensive, but we should probably just ensure
->bdev is NULLed on failure.

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#1447809 — [PATCH v3] Fix NULL pointer dereference in bl_free_device().

FromArtem Savkov <asavkov@redhat.com>
Date2016-07-21 13:40 +0200
Subject[PATCH v3] Fix NULL pointer dereference in bl_free_device().
Message-ID<rXkuC-6Q6-7@gated-at.bofh.it>
In reply to#1447694
When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
blkdev_get_by_*() step we get an pnfs_block_dev struct that is
uninitialized except for bdev field which is set to whatever error
blkdev_get_by_*() returns.  bl_free_device() then tries to call
blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.

Fixing this by setting bdev in struct pnfs_block_dev only if we didn't
get an error from blkdev_get_by_*().

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
 fs/nfs/blocklayout/dev.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
index 118252f..a69ef4e 100644
--- a/fs/nfs/blocklayout/dev.c
+++ b/fs/nfs/blocklayout/dev.c
@@ -235,18 +235,20 @@ bl_parse_simple(struct nfs_server *server, struct pnfs_block_dev *d,
 		struct pnfs_block_volume *volumes, int idx, gfp_t gfp_mask)
 {
 	struct pnfs_block_volume *v = &volumes[idx];
+	struct block_device *bdev;
 	dev_t dev;
 
 	dev = bl_resolve_deviceid(server, v, gfp_mask);
 	if (!dev)
 		return -EIO;
 
-	d->bdev = blkdev_get_by_dev(dev, FMODE_READ | FMODE_WRITE, NULL);
-	if (IS_ERR(d->bdev)) {
+	bdev = blkdev_get_by_dev(dev, FMODE_READ | FMODE_WRITE, NULL);
+	if (IS_ERR(bdev)) {
 		printk(KERN_WARNING "pNFS: failed to open device %d:%d (%ld)\n",
-			MAJOR(dev), MINOR(dev), PTR_ERR(d->bdev));
-		return PTR_ERR(d->bdev);
+			MAJOR(dev), MINOR(dev), PTR_ERR(bdev));
+		return PTR_ERR(bdev);
 	}
+	d->bdev = bdev;
 
 
 	d->len = i_size_read(d->bdev->bd_inode);
@@ -350,17 +352,19 @@ bl_parse_scsi(struct nfs_server *server, struct pnfs_block_dev *d,
 		struct pnfs_block_volume *volumes, int idx, gfp_t gfp_mask)
 {
 	struct pnfs_block_volume *v = &volumes[idx];
+	struct block_device *bdev;
 	const struct pr_ops *ops;
 	int error;
 
 	if (!bl_validate_designator(v))
 		return -EINVAL;
 
-	d->bdev = bl_open_dm_mpath_udev_path(v);
-	if (IS_ERR(d->bdev))
-		d->bdev = bl_open_udev_path(v);
-	if (IS_ERR(d->bdev))
-		return PTR_ERR(d->bdev);
+	bdev = bl_open_dm_mpath_udev_path(v);
+	if (IS_ERR(bdev))
+		bdev = bl_open_udev_path(v);
+	if (IS_ERR(bdev))
+		return PTR_ERR(bdev);
+	d->bdev = bdev;
 
 	d->len = i_size_read(d->bdev->bd_inode);
 	d->map = bl_map_simple;
-- 
2.5.5

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#1447826 — Re: [PATCH v3] Fix NULL pointer dereference in bl_free_device().

From"Benjamin Coddington" <bcodding@redhat.com>
Date2016-07-21 14:30 +0200
SubjectRe: [PATCH v3] Fix NULL pointer dereference in bl_free_device().
Message-ID<rXlgZ-7mV-11@gated-at.bofh.it>
In reply to#1447809
On 21 Jul 2016, at 7:32, Artem Savkov wrote:

> When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
> blkdev_get_by_*() step we get an pnfs_block_dev struct that is
> uninitialized except for bdev field which is set to whatever error
> blkdev_get_by_*() returns.  bl_free_device() then tries to call
> blkdev_put() if bdev is not 0 resulting in a wrong pointer 
> dereference.
>
> Fixing this by setting bdev in struct pnfs_block_dev only if we didn't
> get an error from blkdev_get_by_*().
>
> Signed-off-by: Artem Savkov <asavkov@redhat.com>

Looks good to me.

Reviewed-by: Benjamin Coddington <bcodding@redhat.com>

> ---
>  fs/nfs/blocklayout/dev.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
> index 118252f..a69ef4e 100644
> --- a/fs/nfs/blocklayout/dev.c
> +++ b/fs/nfs/blocklayout/dev.c
> @@ -235,18 +235,20 @@ bl_parse_simple(struct nfs_server *server, 
> struct pnfs_block_dev *d,
>  		struct pnfs_block_volume *volumes, int idx, gfp_t gfp_mask)
>  {
>  	struct pnfs_block_volume *v = &volumes[idx];
> +	struct block_device *bdev;
>  	dev_t dev;
>
>  	dev = bl_resolve_deviceid(server, v, gfp_mask);
>  	if (!dev)
>  		return -EIO;
>
> -	d->bdev = blkdev_get_by_dev(dev, FMODE_READ | FMODE_WRITE, NULL);
> -	if (IS_ERR(d->bdev)) {
> +	bdev = blkdev_get_by_dev(dev, FMODE_READ | FMODE_WRITE, NULL);
> +	if (IS_ERR(bdev)) {
>  		printk(KERN_WARNING "pNFS: failed to open device %d:%d (%ld)\n",
> -			MAJOR(dev), MINOR(dev), PTR_ERR(d->bdev));
> -		return PTR_ERR(d->bdev);
> +			MAJOR(dev), MINOR(dev), PTR_ERR(bdev));
> +		return PTR_ERR(bdev);
>  	}
> +	d->bdev = bdev;
>
>
>  	d->len = i_size_read(d->bdev->bd_inode);
> @@ -350,17 +352,19 @@ bl_parse_scsi(struct nfs_server *server, struct 
> pnfs_block_dev *d,
>  		struct pnfs_block_volume *volumes, int idx, gfp_t gfp_mask)
>  {
>  	struct pnfs_block_volume *v = &volumes[idx];
> +	struct block_device *bdev;
>  	const struct pr_ops *ops;
>  	int error;
>
>  	if (!bl_validate_designator(v))
>  		return -EINVAL;
>
> -	d->bdev = bl_open_dm_mpath_udev_path(v);
> -	if (IS_ERR(d->bdev))
> -		d->bdev = bl_open_udev_path(v);
> -	if (IS_ERR(d->bdev))
> -		return PTR_ERR(d->bdev);
> +	bdev = bl_open_dm_mpath_udev_path(v);
> +	if (IS_ERR(bdev))
> +		bdev = bl_open_udev_path(v);
> +	if (IS_ERR(bdev))
> +		return PTR_ERR(bdev);
> +	d->bdev = bdev;
>
>  	d->len = i_size_read(d->bdev->bd_inode);
>  	d->map = bl_map_simple;
> -- 
> 2.5.5
>
> --
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#1446542

FromAnna Schumaker <Anna.Schumaker@netapp.com>
Date2016-07-19 17:30 +0200
Message-ID<rWF85-5Ir-5@gated-at.bofh.it>
In reply to#1446350
Hi Artem,

On 07/19/2016 07:30 AM, Artem Savkov wrote:
> When bl_parse_deviceid() fails in bl_alloc_deviceid_node() on
> blkdev_get_by_*() step we get an pnfs_block_dev struct that is
> uninitialized except for bdev field which is set to whatever error
> blkdev_get_by_*() returns.  bl_free_device() then tries to call
> blkdev_put() if bdev is not 0 resulting in a wrong pointer dereference.
> 
> Fixing this by making sure bdev is not an error code in bl_free_device().
> 
> Signed-off-by: Artem Savkov <asavkov@redhat.com>
> ---
>  fs/nfs/blocklayout/dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
> index 118252f..7db3af0 100644
> --- a/fs/nfs/blocklayout/dev.c
> +++ b/fs/nfs/blocklayout/dev.c
> @@ -33,7 +33,7 @@ bl_free_device(struct pnfs_block_dev *dev)
>  				pr_err("failed to unregister PR key.\n");
>  		}
>  
> -		if (dev->bdev)
> +		if (dev->bdev && !IS_ERR(dev->bdev))

This looks pretty straightforward, but can you use IS_ERR_OR_NULL() instead?  It accomplishes the same check with slightly cleaner code :)

Thanks,
Anna

>  			blkdev_put(dev->bdev, FMODE_READ | FMODE_WRITE);
>  	}
>  }
>

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