When size equals the current i_size (including 0), the code used to call check_lock_range(filp, i_size, size - 1, WRITE), which computes `size - 1` and can underflow for size==0. Skip the equal case.

Reported-by: Qianchang Zhao pioooooooooip@gmail.com Reported-by: Zhitong Liu liuzhitong1993@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Qianchang Zhao pioooooooooip@gmail.com --- fs/smb/server/vfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c index 891ed2dc2..d068b78a3 100644 --- a/fs/smb/server/vfs.c +++ b/fs/smb/server/vfs.c @@ -828,7 +828,7 @@ int ksmbd_vfs_truncate(struct ksmbd_work *work, if (size < inode->i_size) { err = check_lock_range(filp, size, inode->i_size - 1, WRITE); - } else { + } else if (size > inode->i_size) { err = check_lock_range(filp, inode->i_size, size - 1, WRITE); }