[PATCH] mqueue: correct the type of ro to int

[Edward Adam Davis]

The ro variable, being of type bool, caused the -EROFS return value from
mnt_want_write() to be implicitly converted to 1. This prevented the file
from being correctly acquired, thus triggering the issue reported by
syzbot [1].

Changing the type of ro to int allows the system to correctly identify
the reason for the file open failure.

[1]
KASAN: null-ptr-deref in range [0x0000000000000040-0x0000000000000047]
Call Trace:
 do_mq_open+0x5a0/0x770 ipc/mqueue.c:932
 __do_sys_mq_open ipc/mqueue.c:945 [inline]
 __se_sys_mq_open ipc/mqueue.c:938 [inline]
 __x64_sys_mq_open+0x16a/0x1c0 ipc/mqueue.c:938

Fixes: f2573685bd0c ("ipc: convert do_mq_open() to FD_ADD()")
Reported-by: syzbot+40f42779048f7476e2e0@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=40f42779048f7476e2e0
Tested-by: syzbot+40f42779048f7476e2e0@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
 ipc/mqueue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 56e811f9e5fa..90664d26ec07 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -893,7 +893,7 @@ static int prepare_open(struct dentry *dentry, int oflag, int ro,
 }
 
 static struct file *mqueue_file_open(struct filename *name,
-				     struct vfsmount *mnt, int oflag, bool ro,
+				     struct vfsmount *mnt, int oflag, int ro,
 				     umode_t mode, struct mq_attr *attr)
 {
 	struct dentry *dentry;
-- 
2.43.0