2023-09-18 06:53:09

by Cheng Lin

Subject: [PATCH v4] xfs: introduce protection for drop nlink

From: Cheng Lin <[email protected]>

When abnormal drop_nlink are detected on the inode,
return error, to avoid corruption propagation.

Signed-off-by: Cheng Lin <[email protected]>
---
fs/xfs/xfs_inode.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 9e62cc500..d16cb62ce 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -919,6 +919,14 @@ xfs_droplink(
xfs_trans_t *tp,
xfs_inode_t *ip)
{
+
+ if (VFS_I(ip)->i_nlink == 0) {
+ xfs_alert(ip->i_mount,
+ "%s: Deleting inode %llu with no links.",
+ __func__, ip->i_ino);
+ return -EFSCORRUPTED;
+ }
+
xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);

drop_nlink(VFS_I(ip));
--
2.18.1

2023-09-19 03:32:51

by Darrick J. Wong

Subject: Re: [PATCH v4] xfs: introduce protection for drop nlink

On Mon, Sep 18, 2023 at 02:50:50PM +0800, [email protected] wrote:
> From: Cheng Lin <[email protected]>
>
> When abnormal drop_nlink are detected on the inode,
> return error, to avoid corruption propagation.
>
> Signed-off-by: Cheng Lin <[email protected]>
> ---
> fs/xfs/xfs_inode.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 9e62cc500..d16cb62ce 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -919,6 +919,14 @@ xfs_droplink(
> xfs_trans_t *tp,
> xfs_inode_t *ip)
> {
> +
> + if (VFS_I(ip)->i_nlink == 0) {
> + xfs_alert(ip->i_mount,
> + "%s: Deleting inode %llu with no links.",
> + __func__, ip->i_ino);

We're not deleting the zero-nlink file, since we return without changing
the link count.

Also wondering why this doesn't use XFS_IS_CORRUPT? That macro already
logs a message about there being problems:

struct xfs_mount *mp = ip->i_mount;

if (XFS_IS_CORRUPT(mp, VFS_I(ip)->i_nlink == 0))
return -EFSCORRUPTED;

--D

> + return -EFSCORRUPTED;
> + }
> +
> xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
>
> drop_nlink(VFS_I(ip));
> --
> 2.18.1