[PATCH v2] xfs: introduce protection for drop nlink

[<cheng.lin130@zte.com.cn>]

From: Cheng Lin <cheng.lin130@zte.com.cn>

When abnormal drop_nlink are detected on the inode,
shutdown filesystem, to avoid corruption propagation.

Signed-off-by: Cheng Lin <cheng.lin130@zte.com.cn>
---
 fs/xfs/xfs_fsops.c | 3 +++
 fs/xfs/xfs_inode.c | 9 +++++++++
 fs/xfs/xfs_mount.h | 1 +
 3 files changed, 13 insertions(+)

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 7cb75cb6b..6fc1cfe83 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -543,6 +543,9 @@ xfs_do_force_shutdown(
 	} else if (flags & SHUTDOWN_CORRUPT_ONDISK) {
 		tag = XFS_PTAG_SHUTDOWN_CORRUPT;
 		why = "Corruption of on-disk metadata";
+	} else if (flags & SHUTDOWN_CORRRUPT_ABN) {
+		tag = XFS_PTAG_SHUTDOWN_CORRUPT;
+		why = "Corruption of Abnormal conditions";
 	} else if (flags & SHUTDOWN_DEVICE_REMOVED) {
 		tag = XFS_PTAG_SHUTDOWN_IOERROR;
 		why = "Block device removal";
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 9e62cc500..2d41f2461 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -919,6 +919,15 @@ 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);
+		xfs_force_shutdown(ip->i_mount, SHUTDOWN_CORRRUPT_ABN);
+		return -EFSCORRUPTED;
+	}
+
 	xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);

 	drop_nlink(VFS_I(ip));
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e2866e7fa..dbf36b048 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -459,6 +459,7 @@ void xfs_do_force_shutdown(struct xfs_mount *mp, uint32_t flags, char *fname,
 #define SHUTDOWN_CORRUPT_INCORE	(1u << 3) /* corrupt in-memory structures */
 #define SHUTDOWN_CORRUPT_ONDISK	(1u << 4)  /* corrupt metadata on device */
 #define SHUTDOWN_DEVICE_REMOVED	(1u << 5) /* device removed underneath us */
+#define SHUTDOWN_CORRRUPT_ABN	(1u << 6) /* shutdown from abnormal conditions */

 #define XFS_SHUTDOWN_STRINGS \
 	{ SHUTDOWN_META_IO_ERROR,	"metadata_io" }, \
-- 
2.18.1