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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 <baijiaju1990@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Jia-Ju Bai 2019-07-30 11:28:20 -07:00 committed by Darrick J. Wong
parent 2e616d9f9c
commit afa1d96d14
1 changed files with 5 additions and 1 deletions
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6
fs/xfs/scrub/dabtree.c
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@ -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;
}