Messages in this thread | | | Subject | Re: [PATCH] fs: xfs: Fix possible null-pointer dereferences in xchk_da_btree_block_check_sibling() | From | Jia-Ju Bai <> | Date | Mon, 29 Jul 2019 15:25:04 +0800 |
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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@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); > 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
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