[PATCH] autofs4: check dev ioctl size before allocating

[Ian Kent <raven@themaw.net>]

From: Sasha Levin <sasha.levin@oracle.com>

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>
---
 fs/autofs4/dev-ioctl.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 3182c0e..232e03d 100644
--- 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);
 }