Ping.
On 11/03/2016, 07:32 PM, Jiri Slaby wrote:
> 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 <jsl...@suse.cz>
> Cc: Herbert Xu <herb...@gondor.apana.org.au>
> Cc: "David S. Miller" <da...@davemloft.net> (maintainer:CRYPTO API)
> Reported-by: Sasha Levin <sasha.le...@oracle.com>
> ---
> crypto/algif_hash.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
> index 2d8466f9e49b..32e8a8d797be 100644
> --- a/crypto/algif_hash.c
> +++ b/crypto/algif_hash.c
> @@ -242,7 +242,7 @@ static int hash_accept(struct socket *sock, struct socket
> *newsock, int flags)
> 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;
>
--
js
suse labs
