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 <baijiaju1990@xxxxxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--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
>
