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

From: Artem Savkov
Date: Thu Jul 21 2016 - 07:32:47 EST


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@xxxxxxxxxx>
---
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