On 2019/7/29 12:20, Darrick J. Wong wrote:
On Mon, Jul 29, 2019 at 11:24:01AM +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> --- 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);Indentation here (in xfs we use two spaces)
Okay, I will fix this.
Also, uh, shouldn't we set ds->state->altpath.blk[level].bp to NULL since we've released the buffer?
So I should set ds->state->altpath.blk[level].bp to NULL at the end of the function xchk_da_btree_block_check_sibling()?
Like: 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; Best wishes, Jia-Ju Bai
