[PATCH] KEYS: trusted: dcp: fix NULL dereference in AEAD crypto operation

[David Gstir]

When sealing or unsealing a key blob we currently do not wait for
the AEAD cipher operation to finish and simply return after submitting
the request. If there is some load on the system we can exit before
the cipher operation is done and the buffer we read from/write to
is already removed from the stack. This will e.g. result in NULL
pointer dereference errors in the DCP driver during blob creation.

Fix this by waiting for the AEAD cipher operation to finish before
resuming the seal and unseal calls.

Cc: stable at vger.kernel.org # v6.10+
Fixes: 0e28bf61a5f9 ("KEYS: trusted: dcp: fix leak of blob encryption key")
Reported-by: Parthiban N <parthiban at linumiz.com>
Closes: https://lore.kernel.org/keyrings/254d3bb1-6dbc-48b4-9c08-77df04baee2f@linumiz.com/
Signed-off-by: David Gstir <david at sigma-star.at>
---
 security/keys/trusted-keys/trusted_dcp.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c
index 4edc5bbbcda3..e908c53a803c 100644
--- a/security/keys/trusted-keys/trusted_dcp.c
+++ b/security/keys/trusted-keys/trusted_dcp.c
@@ -133,6 +133,7 @@ static int do_aead_crypto(u8 *in, u8 *out, size_t len, u8 *key, u8 *nonce,
 	struct scatterlist src_sg, dst_sg;
 	struct crypto_aead *aead;
 	int ret;
+	DECLARE_CRYPTO_WAIT(wait);
 
 	aead = crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(aead)) {
@@ -163,8 +164,8 @@ static int do_aead_crypto(u8 *in, u8 *out, size_t len, u8 *key, u8 *nonce,
 	}
 
 	aead_request_set_crypt(aead_req, &src_sg, &dst_sg, len, nonce);
-	aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL,
-				  NULL);
+	aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP,
+				  crypto_req_done, &wait);
 	aead_request_set_ad(aead_req, 0);
 
 	if (crypto_aead_setkey(aead, key, AES_KEYSIZE_128)) {
@@ -174,9 +175,9 @@ static int do_aead_crypto(u8 *in, u8 *out, size_t len, u8 *key, u8 *nonce,
 	}
 
 	if (do_encrypt)
-		ret = crypto_aead_encrypt(aead_req);
+		ret = crypto_wait_req(crypto_aead_encrypt(aead_req), &wait);
 	else
-		ret = crypto_aead_decrypt(aead_req);
+		ret = crypto_wait_req(crypto_aead_decrypt(aead_req), &wait);
 
 free_req:
 	aead_request_free(aead_req);
-- 
2.47.0