Commit b32a7dc8 authored Nov 27, 2017 by Eric Biggers Committed by Herbert Xu Nov 29, 2017

crypto: algif_aead - fix reference counting of null skcipher



In the AEAD interface for AF_ALG, the reference to the "null skcipher"
held by each tfm was being dropped in the wrong place -- when each
af_alg_ctx was freed instead of when the aead_tfm was freed.  As
discovered by syzkaller, a specially crafted program could use this to
cause the null skcipher to be freed while it is still in use.

Fix it by dropping the reference in the right place.

Fixes: 72548b09 ("crypto: algif_aead - copy AAD from src to dst")
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

parent d2890c37

crypto/algif_aead.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -487,6 +487,7 @@ static void aead_release(void *private)
		struct aead_tfm *tfm = private;

		crypto_free_aead(tfm->aead);
		crypto_put_default_null_skcipher2();
		kfree(tfm);
		}

		@@ -519,7 +520,6 @@ static void aead_sock_destruct(struct sock *sk)
		unsigned int ivlen = crypto_aead_ivsize(tfm);

		af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
		crypto_put_default_null_skcipher2();
		sock_kzfree_s(sk, ctx->iv, ivlen);
		sock_kfree_s(sk, ctx, ctx->len);
		af_alg_release_parent(sk);

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