[PATCH 4.4 087/162] crypto: pcrypt - Delay write to padata->info

Greg Kroah-Hartman
2021-11-24T12:09:33Z

From: Daniel Jordan <daniel.m.jordan@oracle.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@syzkaller.appspotmail.com
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.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