linux-kernel - [PATCH] crypto: algif_hash - Remove bogus SGL free on zero-length error path

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Message-ID: <Zbsw1WDUg8mJ5s9e@gondor.apana.org.au>
Date: Thu, 1 Feb 2024 13:49:09 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: xingwei lee <xrivendell7@...il.com>
Cc: syzbot+3266db0c26d1fbbe3abb@...kaller.appspotmail.com,
	davem@...emloft.net, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [PATCH] crypto: algif_hash - Remove bogus SGL free on zero-length
 error path

On Fri, Jan 26, 2024 at 09:11:39PM +0800, xingwei lee wrote:
> This bug is the same bug that is mentioned in
> https://lore.kernel.org/all/20231211135949.689204-1-syoshida@redhat.com/.
> And I also reproduced it with repro.c in
> https://lore.kernel.org/all/CABOYnLxaHBEaSRaEU+kDsHF8a=9AokO1ZUEVtpeT9ddL8giw3A@mail.gmail.com/
> also see in https://gist.github.com/xrivendell7/b10745f297bd2d12a2e48155920996d2
> and also a simple root cause analysis.

Thanks for the reminder.  I was waiting for an updated patch but
I'll apply the following instead:

---8<---
When a zero-length message is hashed by algif_hash, and an error
is triggered, it tries to free an SG list that was never allocated
in the first place.  Fix this by not freeing the SG list on the
zero-length error path.

Reported-by: Shigeru Yoshida <syoshida@...hat.com>
Reported-by: xingwei lee <xrivendell7@...il.com>
Fixes: b6d972f68983 ("crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE)")
Cc: <stable@...r.kernel.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index 82c44d4899b9..e24c829d7a01 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -91,13 +91,13 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
 		if (!(msg->msg_flags & MSG_MORE)) {
 			err = hash_alloc_result(sk, ctx);
 			if (err)
-				goto unlock_free;
+				goto unlock_free_result;
 			ahash_request_set_crypt(&ctx->req, NULL,
 						ctx->result, 0);
 			err = crypto_wait_req(crypto_ahash_final(&ctx->req),
 					      &ctx->wait);
 			if (err)
-				goto unlock_free;
+				goto unlock_free_result;
 		}
 		goto done_more;
 	}
@@ -170,6 +170,7 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
 
 unlock_free:
 	af_alg_free_sg(&ctx->sgl);
+unlock_free_result:
 	hash_free_result(sk, ctx);
 	ctx->more = false;
 	goto unlock;
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt