From: Guo Xuenan <guoxuenan@huawei.com> mainline inclusion from mainline-v6.1-rc4 commit 8c25febf23963431686f04874b96321288504127 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4KIAO CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- xfs_btree_check_block contains debugging knobs. With XFS_DEBUG setting up, turn on the debugging knob can trigger the assert of xfs_btree_islastblock, test script as follows: while true do mount $disk $mountpoint fsstress -d $testdir -l 0 -n 10000 -p 4 >/dev/null echo 1 > /sys/fs/xfs/sda/errortag/btree_chk_sblk sleep 10 umount $mountpoint done Kick off fsstress and only *then* turn on the debugging knob. If it happens that the knob gets turned on after the cntbt lookup succeeds but before the call to xfs_btree_islastblock, then we *can* end up in the situation where a previously checked btree block suddenly starts returning EFSCORRUPTED from xfs_btree_check_block. Kaboom. Darrick give a very detailed explanation as follows: Looking back at commit 27d9ee577dcce, I think the point of all this was to make sure that the cursor has actually performed a lookup, and that the btree block at whatever level we're asking about is ok. If the caller hasn't ever done a lookup, the bc_levels array will be empty, so cur->bc_levels[level].bp pointer will be NULL. The call to xfs_btree_get_block will crash anyway, so the "ASSERT(block);" part is pointless. If the caller did a lookup but the lookup failed due to block corruption, the corresponding cur->bc_levels[level].bp pointer will also be NULL, and we'll still crash. The "ASSERT(xfs_btree_check_block);" logic is also unnecessary. If the cursor level points to an inode root, the block buffer will be incore, so it had better always be consistent. If the caller ignores a failed lookup after a successful one and calls this function, the cursor state is garbage and the assert wouldn't have tripped anyway. So get rid of the assert. Fixes: 27d9ee577dcc ("xfs: actually check xfs_btree_check_block return in xfs_btree_islastblock") Signed-off-by: Guo Xuenan <guoxuenan@huawei.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Guo Xuenan <guoxuenan@huawei.com> Reviewed-by: Zhang Yi <yi.zhang@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/xfs/libxfs/xfs_btree.h | 1 - 1 file changed, 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h index 10e50cbacacf..ba11d2a4b686 100644 --- a/fs/xfs/libxfs/xfs_btree.h +++ b/fs/xfs/libxfs/xfs_btree.h @@ -523,7 +523,6 @@ xfs_btree_islastblock( struct xfs_buf *bp; block = xfs_btree_get_block(cur, level, &bp); - ASSERT(block && xfs_btree_check_block(cur, block, level, bp) == 0); if (cur->bc_flags & XFS_BTREE_LONG_PTRS) return block->bb_u.l.bb_rightsib == cpu_to_be64(NULLFSBLOCK); -- 2.20.1