[PATCH 6.1 208/232] fs/ntfs3: prevent infinite loops caused by the next valid being the same

Sasha Levin
2026-02-28T18:14:25Z

From: Edward Adam Davis <eadavis@qq.com>

[ Upstream commit 27b75ca4e51e3e4554dc85dbf1a0246c66106fd3 ]

When processing valid within the range [valid : pos), if valid cannot
be retrieved correctly, for example, if the retrieved valid value is
always the same, this can trigger a potential infinite loop, similar
to the hung problem reported by syzbot [1].

Adding a check for the valid value within the loop body, and terminating
the loop and returning -EINVAL if the value is the same as the current
value, can prevent this.

[1]
INFO: task syz.4.21:6056 blocked for more than 143 seconds.
Call Trace:
rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
inode_lock include/linux/fs.h:1027 [inline]
ntfs_file_write_iter+0xe6/0x870 fs/ntfs3/file.c:1284

Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
Reported-by: syzbot+bcf9e1868c1a0c7e04f1@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=bcf9e1868c1a0c7e04f1
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ntfs3/file.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 6d9c1dfe9b1b6..f2d1df2c988a9 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -870,8 +870,12 @@ static ssize_t ntfs_compress_write(struct kiocb *iocb, struct iov_iter *from)
goto out;

if (lcn == SPARSE_LCN) {
- ni->i_valid = valid =
- frame_vbo + ((u64)clen << sbi->cluster_bits);
+ valid = frame_vbo + ((u64)clen << sbi->cluster_bits);
+ if (ni->i_valid == valid) {
+ err = -EINVAL;
+ goto out;
+ }
+ ni->i_valid = valid;
continue;
}

--
2.51.0