linux-kernel - [PATCH 4.19 173/323] crypto: pcrypt

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Date:   Wed, 24 Nov 2021 12:56:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+b187b77c8474f9648fae@...kaller.appspotmail.com,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 173/323] crypto: pcrypt - Delay write to padata->info

From: Daniel Jordan <daniel.m.jordan@...cle.com>

[ Upstream commit 68b6dea802cea0dbdd8bd7ccc60716b5a32a5d8a ]

These three events can race when pcrypt is used multiple times in a
template ("pcrypt(pcrypt(...))"):

  1.  [taskA] The caller makes the crypto request via crypto_aead_encrypt()
  2.  [kworkerB] padata serializes the inner pcrypt request
  3.  [kworkerC] padata serializes the outer pcrypt request

3 might finish before the call to crypto_aead_encrypt() returns in 1,
resulting in two possible issues.

First, a use-after-free of the crypto request's memory when, for
example, taskA writes to the outer pcrypt request's padata->info in
pcrypt_aead_enc() after kworkerC completes the request.

Second, the outer pcrypt request overwrites the inner pcrypt request's
return code with -EINPROGRESS, making a successful request appear to
fail.  For instance, kworkerB writes the outer pcrypt request's
padata->info in pcrypt_aead_done() and then taskA overwrites it
in pcrypt_aead_enc().

Avoid both situations by delaying the write of padata->info until after
the inner crypto request's return code is checked.  This prevents the
use-after-free by not touching the crypto request's memory after the
next-inner crypto request is made, and stops padata->info from being
overwritten.

Fixes: 5068c7a883d16 ("crypto: pcrypt - Add pcrypt crypto parallelization wrapper")
Reported-by: syzbot+b187b77c8474f9648fae@...kaller.appspotmail.com
Signed-off-by: Daniel Jordan <daniel.m.jordan@...cle.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 crypto/pcrypt.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
index 85082574c5154..62e11835f220e 100644
--- a/crypto/pcrypt.c
+++ b/crypto/pcrypt.c
@@ -138,12 +138,14 @@ static void pcrypt_aead_enc(struct padata_priv *padata)
 {
 	struct pcrypt_request *preq = pcrypt_padata_request(padata);
 	struct aead_request *req = pcrypt_request_ctx(preq);
+	int ret;

-	padata->info = crypto_aead_encrypt(req);
+	ret = crypto_aead_encrypt(req);

-	if (padata->info == -EINPROGRESS)
+	if (ret == -EINPROGRESS)
 		return;

+	padata->info = ret;
 	padata_do_serial(padata);
 }

@@ -180,12 +182,14 @@ static void pcrypt_aead_dec(struct padata_priv *padata)
 {
 	struct pcrypt_request *preq = pcrypt_padata_request(padata);
 	struct aead_request *req = pcrypt_request_ctx(preq);
+	int ret;

-	padata->info = crypto_aead_decrypt(req);
+	ret = crypto_aead_decrypt(req);

-	if (padata->info == -EINPROGRESS)
+	if (ret == -EINPROGRESS)
 		return;

+	padata->info = ret;
 	padata_do_serial(padata);
 }

-- 
2.33.0