[PATCH] fix posix lock on NFS

NFS client prevents mandatory lock, but there is a flaw on it; Locks are
possibly left if the mode is changed while locking.

This permits unlocking even if the mandatory lock bits are set.

Signed-off-by: ASANO Masahiro <masano@tnes.nec.co.jp>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index eb5cd4c..7a79fbe 100644 (file)
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -509,7 +509,8 @@ static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
                return -EINVAL;
 
        /* No mandatory locks over NFS */
-       if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+       if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
+           fl->fl_type != F_UNLCK)
                return -ENOLCK;
 
        if (IS_GETLK(cmd))