Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932985AbdC1Nk0 (ORCPT ); Tue, 28 Mar 2017 09:40:26 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59154 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753555AbdC1Mfm (ORCPT ); Tue, 28 Mar 2017 08:35:42 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiri Slaby , Herbert Xu , Sasha Levin , Arnd Bergmann , "David S. Miller" Subject: [PATCH 4.4 76/76] crypto: algif_hash - avoid zero-sized array Date: Tue, 28 Mar 2017 14:31:13 +0200 Message-Id: <20170328122603.041947597@linuxfoundation.org> X-Mailer: git-send-email 2.12.1 In-Reply-To: <20170328122559.966310440@linuxfoundation.org> References: <20170328122559.966310440@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2512 Lines: 71 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Slaby commit 6207119444595d287b1e9e83a2066c17209698f3 upstream. With this reproducer: struct sockaddr_alg alg = { .salg_family = 0x26, .salg_type = "hash", .salg_feat = 0xf, .salg_mask = 0x5, .salg_name = "digest_null", }; int sock, sock2; sock = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(sock, (struct sockaddr *)&alg, sizeof(alg)); sock2 = accept(sock, NULL, NULL); setsockopt(sock, SOL_ALG, ALG_SET_KEY, "\x9b\xca", 2); accept(sock2, NULL, NULL); ==== 8< ======== 8< ======== 8< ======== 8< ==== one can immediatelly see an UBSAN warning: UBSAN: Undefined behaviour in crypto/algif_hash.c:187:7 variable length array bound value 0 <= 0 CPU: 0 PID: 15949 Comm: syz-executor Tainted: G E 4.4.30-0-default #1 ... Call Trace: ... [] ? __ubsan_handle_vla_bound_not_positive+0x13d/0x188 [] ? __ubsan_handle_out_of_bounds+0x1bc/0x1bc [] ? hash_accept+0x5bd/0x7d0 [algif_hash] [] ? hash_accept_nokey+0x3f/0x51 [algif_hash] [] ? hash_accept_parent_nokey+0x4a0/0x4a0 [algif_hash] [] ? SyS_accept+0x2b/0x40 It is a correct warning, as hash state is propagated to accept as zero, but creating a zero-length variable array is not allowed in C. Fix this as proposed by Herbert -- do "?: 1" on that site. No sizeof or similar happens in the code there, so we just allocate one byte even though we do not use the array. Signed-off-by: Jiri Slaby Cc: Herbert Xu Cc: "David S. Miller" (maintainer:CRYPTO API) Reported-by: Sasha Levin Signed-off-by: Herbert Xu Cc: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- crypto/algif_hash.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/crypto/algif_hash.c +++ b/crypto/algif_hash.c @@ -184,7 +184,7 @@ static int hash_accept(struct socket *so struct alg_sock *ask = alg_sk(sk); struct hash_ctx *ctx = ask->private; struct ahash_request *req = &ctx->req; - char state[crypto_ahash_statesize(crypto_ahash_reqtfm(req))]; + char state[crypto_ahash_statesize(crypto_ahash_reqtfm(req)) ? : 1]; struct sock *sk2; struct alg_sock *ask2; struct hash_ctx *ctx2;