linux-kernel - Re: KASAN: use-after-free Read in aead

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Message-ID: <20171129052305.GA19831@gondor.apana.org.au>
Date:   Wed, 29 Nov 2017 16:23:05 +1100
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     Stephan Mueller <smueller@...onox.de>,
        syzbot 
        <bot+6fbc13c3b1ed2105e7a2e516be43d6a0624a59c0@...kaller.appspotmail.com>,
        davem@...emloft.net, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: use-after-free Read in aead_recvmsg

On Mon, Nov 27, 2017 at 11:29:44PM -0800, Eric Biggers wrote:
>
> >From 453b54793e843c0d5b8fd2d5e33fcc5427ec038e Mon Sep 17 00:00:00 2001
> From: Eric Biggers <ebiggers@...gle.com>
> Date: Mon, 27 Nov 2017 23:23:05 -0800
> Subject: [PATCH] crypto: algif_aead - fix reference counting of null skcipher
> 
> In the AEAD interface for AF_ALG, the reference to the "null skcipher"
> held by each tfm was being dropped in the wrong place -- when each
> af_alg_ctx was freed instead of when the aead_tfm was freed.  As
> discovered by syzkaller, a specially crafted program could use this to
> cause the null skcipher to be freed while it is still in use.
> 
> Fix it by dropping the reference in the right place.
> 
> Fixes: 72548b093ee3 ("crypto: algif_aead - copy AAD from src to dst")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Cc: <stable@...r.kernel.org> # v4.14+
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt