| Message ID | 20161117140757.GA1149@gondor.apana.org.au (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Herbert Xu |
| Headers | show |
On 11/17/2016 06:07 AM, Herbert Xu wrote: > On Wed, Nov 16, 2016 at 11:17:33AM -0800, Mat Martineau wrote: >> >> Herbert - >> >> Following commit 493b2ed3f7603a15ff738553384d5a4510ffeb95, there is a NULL >> dereference crash in algif_hash when recv() is called twice like this: >> >> send(sk, data, len, MSG_MORE); >> recv(sk, hash1, len, 0); >> recv(sk, hash2, len, 0); >> >> In 4.8 and earlier, the two recvs return identical data. In 4.9-rc5, the >> second recv triggers this: >> >> [ 53.041287] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 >> [ 53.042048] IP: [<ffffffffa73fdfb3>] shash_ahash_digest+0x23/0x130 > > Ugh. It looks like the shash wrapper is incorrectly dereferencing > the SG list even when the length is zero. Rather than fixing it > I'm just going to make algif_hash do the safe thing of doing an > init followed by a final. > > Thanks, > > ---8<--- > Subject: crypto: algif_hash - Fix NULL hash crash with shash > > Recently algif_hash has been changed to allow null hashes. This > triggers a bug when used with an shash algorithm whereby it will > cause a crash during the digest operation. > > This patch fixes it by avoiding the digest operation and instead > doing an init followed by a final which avoids the buggy code in > shash. > > This patch also ensures that the result buffer is freed after an > error so that it is not returned as a genuine hash result on the > next recv call. > > The shash/ahash wrapper code will be fixed later to handle this > case correctly. > > Fixes: 493b2ed3f760 ("crypto: algif_hash - Handle NULL hashes correctly") > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> > > diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c > index 2d8466f..05e21b4 100644 > --- a/crypto/algif_hash.c > +++ b/crypto/algif_hash.c > @@ -214,23 +214,26 @@ static int hash_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, > > ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0); > > - if (ctx->more) { > + if (!result) { > + err = af_alg_wait_for_completion( > + crypto_ahash_init(&ctx->req), > + &ctx->completion); > + if (err) > + goto unlock; > + } > + > + if (!result || ctx->more) { > ctx->more = 0; > err = af_alg_wait_for_completion(crypto_ahash_final(&ctx->req), > &ctx->completion); > if (err) > goto unlock; > - } else if (!result) { > - err = af_alg_wait_for_completion( > - crypto_ahash_digest(&ctx->req), > - &ctx->completion); > } > > err = memcpy_to_msg(msg, ctx->result, len); > > - hash_free_result(sk, ctx); > - > unlock: > + hash_free_result(sk, ctx); > release_sock(sk); > > return err ?: len; > Confirmed to work for me. You can take that as a Tested-by. Thanks, Laura -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c index 2d8466f..05e21b4 100644 --- a/crypto/algif_hash.c +++ b/crypto/algif_hash.c @@ -214,23 +214,26 @@ static int hash_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0); - if (ctx->more) { + if (!result) { + err = af_alg_wait_for_completion( + crypto_ahash_init(&ctx->req), + &ctx->completion); + if (err) + goto unlock; + } + + if (!result || ctx->more) { ctx->more = 0; err = af_alg_wait_for_completion(crypto_ahash_final(&ctx->req), &ctx->completion); if (err) goto unlock; - } else if (!result) { - err = af_alg_wait_for_completion( - crypto_ahash_digest(&ctx->req), - &ctx->completion); } err = memcpy_to_msg(msg, ctx->result, len); - hash_free_result(sk, ctx); - unlock: + hash_free_result(sk, ctx); release_sock(sk); return err ?: len;