2019-07-30 04:54:48

by Jia-Ju Bai

Subject: [PATCH v2] fs: xfs: Fix possible null-pointer dereferences in xchk_da_btree_block_check_sibling()

In xchk_da_btree_block_check_sibling(), there is an if statement on
line 274 to check whether ds->state->altpath.blk[level].bp is NULL:
if (ds->state->altpath.blk[level].bp)

When ds->state->altpath.blk[level].bp is NULL, it is used on line 281:
xfs_trans_brelse(..., ds->state->altpath.blk[level].bp);
struct xfs_buf_log_item *bip = bp->b_log_item;
ASSERT(bp->b_transp == tp);

Thus, possible null-pointer dereferences may occur.

To fix these bugs, ds->state->altpath.blk[level].bp is checked before
being used.

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
v2:
* Adjust the code and add an assignment.
Thank Darrick J. Wong for helpful advice.

---
fs/xfs/scrub/dabtree.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/scrub/dabtree.c b/fs/xfs/scrub/dabtree.c
index 94c4f1de1922..77ff9f97bcda 100644
--- a/fs/xfs/scrub/dabtree.c
+++ b/fs/xfs/scrub/dabtree.c
@@ -278,7 +278,11 @@ xchk_da_btree_block_check_sibling(
/* Compare upper level pointer to sibling pointer. */
if (ds->state->altpath.blk[level].blkno != sibling)
xchk_da_set_corrupt(ds, level);
- xfs_trans_brelse(ds->dargs.trans, ds->state->altpath.blk[level].bp);
+ if (ds->state->altpath.blk[level].bp) {
+ xfs_trans_brelse(ds->dargs.trans,
+ ds->state->altpath.blk[level].bp);
+ ds->state->altpath.blk[level].bp = NULL;
+ }
out:
return error;
}
--
2.17.0

2019-07-30 16:35:54

by Darrick J. Wong

Subject: Re: [PATCH v2] fs: xfs: Fix possible null-pointer dereferences in xchk_da_btree_block_check_sibling()

On Tue, Jul 30, 2019 at 10:32:06AM +0800, Jia-Ju Bai wrote:
> In xchk_da_btree_block_check_sibling(), there is an if statement on
> line 274 to check whether ds->state->altpath.blk[level].bp is NULL:
> if (ds->state->altpath.blk[level].bp)
>
> When ds->state->altpath.blk[level].bp is NULL, it is used on line 281:
> xfs_trans_brelse(..., ds->state->altpath.blk[level].bp);
> struct xfs_buf_log_item *bip = bp->b_log_item;
> ASSERT(bp->b_transp == tp);
>
> Thus, possible null-pointer dereferences may occur.
>
> To fix these bugs, ds->state->altpath.blk[level].bp is checked before
> being used.
>
> These bugs are found by a static analysis tool STCheck written by us.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>

Looks ok,
Reviewed-by: Darrick J. Wong <[email protected]>

--D

> ---
> v2:
> * Adjust the code and add an assignment.
> Thank Darrick J. Wong for helpful advice.
>
> ---
> fs/xfs/scrub/dabtree.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/scrub/dabtree.c b/fs/xfs/scrub/dabtree.c
> index 94c4f1de1922..77ff9f97bcda 100644
> --- a/fs/xfs/scrub/dabtree.c
> +++ b/fs/xfs/scrub/dabtree.c
> @@ -278,7 +278,11 @@ xchk_da_btree_block_check_sibling(
> /* Compare upper level pointer to sibling pointer. */
> if (ds->state->altpath.blk[level].blkno != sibling)
> xchk_da_set_corrupt(ds, level);
> - xfs_trans_brelse(ds->dargs.trans, ds->state->altpath.blk[level].bp);
> + if (ds->state->altpath.blk[level].bp) {
> + xfs_trans_brelse(ds->dargs.trans,
> + ds->state->altpath.blk[level].bp);
> + ds->state->altpath.blk[level].bp = NULL;
> + }
> out:
> return error;
> }
> --
> 2.17.0
>