This is a note to let you know that I've just added the patch titled
crypto: algif_hash - avoid zero-sized array
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
crypto-algif_hash-avoid-zero-sized-array.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6207119444595d287b1e9e83a2066c17209698f3 Mon Sep 17 00:00:00 2001
From: Jiri Slaby <jslaby@xxxxxxx>
Date: Thu, 15 Dec 2016 14:31:01 +0100
Subject: crypto: algif_hash - avoid zero-sized array
From: Jiri Slaby <jslaby@xxxxxxx>
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:
...
[<ffffffff81d598fd>] ? __ubsan_handle_vla_bound_not_positive+0x13d/0x188
[<ffffffff81d597c0>] ? __ubsan_handle_out_of_bounds+0x1bc/0x1bc
[<ffffffffa0e2204d>] ? hash_accept+0x5bd/0x7d0 [algif_hash]
[<ffffffffa0e2293f>] ? hash_accept_nokey+0x3f/0x51 [algif_hash]
[<ffffffffa0e206b0>] ? hash_accept_parent_nokey+0x4a0/0x4a0 [algif_hash]
[<ffffffff8235c42b>] ? 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 <jslaby@xxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> (maintainer:CRYPTO API)
Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
crypto/algif_hash.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -245,7 +245,7 @@ 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;
Patches currently in stable-queue which might be from jslaby@xxxxxxx are
queue-4.9/crypto-algif_hash-avoid-zero-sized-array.patch