[PATCH v7 3/7] locks: Disable LOCK_MAND support for MS_SHARELOCK mounts

[Pavel Shilovsky <piastry@etersoft.ru>]

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
---
 fs/locks.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/locks.c b/fs/locks.c
index 7ecc511..c7e780a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1904,6 +1904,12 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
 		goto out;
 	}
 
+	/* Disable LOCK_MAND support for FS mounted with MS_SHARELOCK */
+	if ((cmd & LOCK_MAND) && IS_SHARELOCK(f.file->f_path.dentry->d_inode)) {
+		error = -EPERM;
+		goto out;
+	}
+
 	can_sleep = !(cmd & LOCK_NB);
 	cmd &= ~LOCK_NB;
 	unlock = (cmd == LOCK_UN);
-- 
1.7.10.4