From: Jiri Slaby jslaby@suse.cz
This patch has been added to the stable tree. If you have any objections, please let us know.
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[ Upstream commit 6207119444595d287b1e9e83a2066c17209698f3 ]
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@suse.cz Cc: Herbert Xu herbert@gondor.apana.org.au Cc: "David S. Miller" davem@davemloft.net (maintainer:CRYPTO API) Reported-by: Sasha Levin sasha.levin@oracle.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Sasha Levin alexander.levin@microsoft.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 d7a3435280d8..db83dabe5fc9 100644 --- a/crypto/algif_hash.c +++ b/crypto/algif_hash.c @@ -184,7 +184,7 @@ 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;