linux-kernel - Re: [PATCH] KEYS: fix dereferencing NULL payload with nonzero length

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Message-ID: <6884.1491247244@warthog.procyon.org.uk>
Date:   Mon, 03 Apr 2017 20:20:44 +0100
From:   David Howells <dhowells@...hat.com>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     dhowells@...hat.com, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] KEYS: fix dereferencing NULL payload with nonzero length

Eric Biggers <ebiggers3@...il.com> wrote:

> > > -	if (_payload) {
> > > +	if (plen) {
> > 
> > "if (_payload && plen)" would be better.
> > 
> > David
> 
> No, that doesn't solve the problem.  The problem is that userspace can pass
> in a NULL payload with nonzero length, causing the kernel to dereference a
> NULL pointer for some key types.  For example:

Okay, in that case, I think there should be an else-statement that clears plen
if !_payload.

David