Re: [PATCH] btrfs: fix array index in qgroup_auto_inherit()

From: Qu Wenruo
Date: Sat May 04 2024 - 18:42:20 EST




在 2024/5/4 21:08, Dan Carpenter 写道:
The "i++" was accidentally left out so it just sets qgids[0] over and
over.

Fixes: 5343cd9364ea ("btrfs: qgroup: simple quota auto hierarchy for nested subvolumes")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

It is indeed the case, btrfs_qgroup_inherit::groups[] should be the
parent qgroupis the subvolume would be added to.

In fact this can lead to unexpected problems, as the groups[1:] would be
all 0, leading to later find_qgroup_rb() unable to find a qgroup and
cause snapshot creation failure.

IMHO you can also craft a fstest case, where the parent subvolume is
assgined to multiple qgroups, and creating a new subvolume inside that
one, which should lead to subvolume creation failure.

Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>

Thanks,
Qu
---
From static analysis. Untested.

fs/btrfs/qgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 2ca6bbc1bcc9..1284e78fffce 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3121,7 +3121,7 @@ static int qgroup_auto_inherit(struct btrfs_fs_info *fs_info,
qgids = res->qgroups;

list_for_each_entry(qg_list, &inode_qg->groups, next_group)
- qgids[i] = qg_list->group->qgroupid;
+ qgids[i++] = qg_list->group->qgroupid;

*inherit = res;
return 0;