[PATCH v2 4/4] f2fs: require write permission for F2FS_IOC_IO_PRIO

[Hungyu Lin <dennylin0707@gmail.com>]

F2FS_IOC_IO_PRIO does not check who the caller is, so any user who can
open a file, even read-only, can set its write I/O priority hint.

Require write permission on the inode.

Fixes: 5f95c1812a65 ("f2fs: add ioctl to get IO priority hint")
Suggested-by: Chao Yu <chao@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
 fs/f2fs/file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 9d09ce597f72..e25c7166c367 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3985,6 +3985,9 @@ static int f2fs_ioc_io_prio(struct file *filp, unsigned long arg)
 	if (!S_ISREG(inode->i_mode) || level >= F2FS_IOPRIO_MAX)
 		return -EINVAL;
 
+	if (inode_permission(file_mnt_idmap(filp), inode, MAY_WRITE))
+		return -EACCES;
+
 	inode_lock(inode);
 	F2FS_I(inode)->ioprio_hint = level;
 	inode_unlock(inode);
-- 
2.43.0