autofs4: check dev ioctl size before allocating

commit e53d77eb8bb616e903e34cc7a918401bee3b5149 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index de54271..868101c 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);
 }