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Subject[PATCH] fs: xfs: Fix possible null-pointer dereferences in xchk_da_btree_block_check_sibling()
Date
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@gmail.com>
---
fs/xfs/scrub/dabtree.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/scrub/dabtree.c b/fs/xfs/scrub/dabtree.c
index 94c4f1de1922..33ff90c0dd70 100644
--- a/fs/xfs/scrub/dabtree.c
+++ b/fs/xfs/scrub/dabtree.c
@@ -278,7 +278,9 @@ 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);
out:
return error;
}
--
2.17.0
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