Re: [PATCH] net: socket: don't set sk_uid to garbage value in ->setattr()

[David Miller]

From: Eric Biggers <ebiggers3@xxxxxxxxx>
Date: Fri, 30 Dec 2016 17:42:32 -0600

> From: Eric Biggers <ebiggers@xxxxxxxxxx>
> 
> ->setattr() was recently implemented for socket files to sync the socket
> inode's uid to the new 'sk_uid' member of struct sock.  It does this by
> copying over the ia_uid member of struct iattr.  However, ia_uid is
> actually only valid when ATTR_UID is set in ia_valid, indicating that
> the uid is being changed, e.g. by chown.  Other metadata operations such
> as chmod or utimes leave ia_uid uninitialized.  Therefore, sk_uid could
> be set to a "garbage" value from the stack.
> 
> Fix this by only copying the uid over when ATTR_UID is set.
> 
> Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>

Lorenzo, please review.