Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
        Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
        Kingdom.
        Registered in England and Wales under Company Registration No. 3798903
From:   David Howells <dhowells@redhat.com>
In-Reply-To: <CAAUqJDuRkHE8fPgZJGaKjUjd3QfGwzfumuJBmStPqBhubxyk_A@mail.gmail.com>
References: <CAAUqJDuRkHE8fPgZJGaKjUjd3QfGwzfumuJBmStPqBhubxyk_A@mail.gmail.com>
To:     =?us-ascii?Q?=3D=3FUTF-8=3FB=3FT25kcmVqIE1vc27DocSNZWs=3D=3F=3D?= 
        <omosnacek@gmail.com>, Herbert Xu <herbert@gondor.apana.org.au>
Cc:     dhowells@redhat.com, Paolo Abeni <pabeni@redhat.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Harald Freudenberger <freude@linux.vnet.ibm.com>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        linux-crypto@vger.kernel.org, linux-s390@vger.kernel.org,
        netdev@vger.kernel.org, regressions@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: [PATCH] crypto: Fix missing initialisation affecting gcm-aes-s390
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Date:   Wed, 26 Jul 2023 22:53:19 +0100
Message-ID: <97730.1690408399@warthog.procyon.org.uk>
Precedence: bulk

=20=20=20=20
Fix af_alg_alloc_areq() to initialise areq->first_rsgl.sgl.sgt.sgl to point
to the scatterlist array in areq->first_rsgl.sgl.sgl.

Without this, the gcm-aes-s390 driver will oops when it tries to do
gcm_walk_start() on req->dst because req->dst is set to the value of
areq->first_rsgl.sgl.sgl by _aead_recvmsg() calling
aead_request_set_crypt().

The problem comes if an empty ciphertext is passed: the loop in
af_alg_get_rsgl() just passes straight out and doesn't set areq->first_rsgl
up.

This isn't a problem on x86_64 using gcmaes_crypt_by_sg() because, as far
as I can tell, that ignores req->dst and only uses req->src[*].

[*] Is this a bug in aesni-intel_glue.c?

The s390x oops looks something like:

 Unable to handle kernel pointer dereference in virtual kernel address space
 Failing address: 0000000a00000000 TEID: 0000000a00000803
 Fault in home space mode while using kernel ASCE.
 AS:00000000a43a0007 R3:0000000000000024
 Oops: 003b ilc:2 [#1] SMP
 ...
 Call Trace:
  [<000003ff7fc3d47e>] gcm_walk_start+0x16/0x28 [aes_s390]
  [<00000000a2a342f2>] crypto_aead_decrypt+0x9a/0xb8
  [<00000000a2a60888>] aead_recvmsg+0x478/0x698
  [<00000000a2e519a0>] sock_recvmsg+0x70/0xb0
  [<00000000a2e51a56>] sock_read_iter+0x76/0xa0
  [<00000000a273e066>] vfs_read+0x26e/0x2a8
  [<00000000a273e8c4>] ksys_read+0xbc/0x100
  [<00000000a311d808>] __do_syscall+0x1d0/0x1f8
  [<00000000a312ff30>] system_call+0x70/0x98
 Last Breaking-Event-Address:
  [<000003ff7fc3e6b4>] gcm_aes_crypt+0x104/0xa68 [aes_s390]

Fixes: c1abe6f570af ("crypto: af_alg: Use extract_iter_to_sg() to create sc=
atterlists")
Reported-by: Ondrej Mosn=C3=A1=C4=8Dek <omosnacek@gmail.com>
Link: https://lore.kernel.org/r/CAAUqJDuRkHE8fPgZJGaKjUjd3QfGwzfumuJBmStPqB=
hubxyk_A@mail.gmail.com/
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: Sven Schnelle <svens@linux.ibm.com>
cc: Harald Freudenberger <freude@linux.vnet.ibm.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-crypto@vger.kernel.org
cc: linux-s390@vger.kernel.org
cc: regressions@lists.linux.dev
---
 crypto/af_alg.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 06b15b9f661c..9ee8575d3b1a 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1192,6 +1192,7 @@ struct af_alg_async_req *af_alg_alloc_areq(struct soc=
k *sk,
=20
 	areq->areqlen =3D areqlen;
 	areq->sk =3D sk;
+	areq->first_rsgl.sgl.sgt.sgl =3D areq->first_rsgl.sgl.sgl;
 	areq->last_rsgl =3D NULL;
 	INIT_LIST_HEAD(&areq->rsgl_list);
 	areq->tsgl =3D NULL;