[PATCH 03/21] fcntl: refuse F_SET_RW_HINT on an immutable inode

[Christian Brauner]

An immutable inode is never written to so write hints are pointless.
Refuse the hint on an immutable inode the way setattr(), fallocate() and
etxattr() refuse their changes.

Fixes: c75b1d9421f8 ("fs: add fcntl() interface for setting/getting write life time hints")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>
---
 fs/fcntl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index c158f082f1da..9b71bc9d71d1 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -372,6 +372,9 @@ static long fcntl_set_rw_hint(struct file *file, unsigned long arg)
 	u64 __user *argp = (u64 __user *)arg;
 	u64 hint;
 
+	/* nothing is ever written to it */
+	if (IS_IMMUTABLE(inode))
+		return -EPERM;
 	if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
 		return -EPERM;
 

-- 
2.53.0