autofs4: check dev ioctl size before allocating

There wasn't any check of the size passed from userspace before trying
to allocate the memory required.

This meant that userspace might request more space than allowed,
triggering an OOM.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 3182c0e68b4204cb2aec089b5d960b7053534757..232e03d4780d1b51386e72ab8df7e65af279e8ff 100644 (file)
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -103,6 +103,9 @@ static struct autofs_dev_ioctl *copy_dev_ioctl(struct autofs_dev_ioctl __user *i
        if (tmp.size < sizeof(tmp))
                return ERR_PTR(-EINVAL);
 
+       if (tmp.size > (PATH_MAX + sizeof(tmp)))
+               return ERR_PTR(-ENAMETOOLONG);
+
        return memdup_user(in, tmp.size);
 }