[PATCH v3 2/3] s390/crypto: Fix missing scrub of temp buffers with AES ctr and gcm algorithm

In function ctr_aes_crypt() there is a buffer used to process
remaining bytes < AES_BLOCK_SIZE. This buffer was not scrubbed and
thus could lead to expose of unwanted data. When the buffer is used
explicitly scrub it at the end of the code block to avoid exposure of
maybe sensitive data.

In a similar way the function gcm_aes_crypt() hat an error path where
the CPACF param block was not scrubbed. Instead of return early now
these error paths go to end of function where explicit scrubbing is
done. Similar with the buffers which are part of the gcm_sg_walk
structs from the variables gw_in and gw_out.

Fixes: d07f951903fa ("crypto: s390/aes - Fix buffer overread in CTR mode")
Signed-off-by: Harald Freudenberger <[email protected]>
Cc: [email protected] # 6.8+
---
 arch/s390/crypto/aes_s390.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/s390/crypto/aes_s390.c b/arch/s390/crypto/aes_s390.c
index 366ce22d3623..10561aa687c7 100644
--- a/arch/s390/crypto/aes_s390.c
+++ b/arch/s390/crypto/aes_s390.c
@@ -604,6 +604,7 @@ static int ctr_aes_crypt(struct skcipher_request *req)
 		memcpy(walk.dst.virt.addr, buf, nbytes);
 		crypto_inc(walk.iv, AES_BLOCK_SIZE);
 		ret = skcipher_walk_done(&walk, 0);
+		memzero_explicit(buf, sizeof(buf));
 	}
 
 	return ret;
@@ -895,10 +896,14 @@ static int gcm_aes_crypt(struct aead_request *req, unsigned int flags)
 			  gw_in.ptr, aad_bytes);
 
 		n = aad_bytes + pc_bytes;
-		if (gcm_in_walk_done(&gw_in, n) != n)
-			return -ENOMEM;
-		if (gcm_out_walk_done(&gw_out, n) != n)
-			return -ENOMEM;
+		if (gcm_in_walk_done(&gw_in, n) != n) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		if (gcm_out_walk_done(&gw_out, n) != n) {
+			ret = -ENOMEM;
+			goto out;
+		}
 		aadlen -= aad_bytes;
 		pclen -= pc_bytes;
 	} while (aadlen + pclen > 0);
@@ -910,7 +915,10 @@ static int gcm_aes_crypt(struct aead_request *req, unsigned int flags)
 	} else
 		scatterwalk_map_and_copy(param.t, req->dst, len, taglen, 1);
 
+out:
 	memzero_explicit(&param, sizeof(param));
+	memzero_explicit(gw_in.buf, sizeof(gw_in.buf));
+	memzero_explicit(gw_out.buf, sizeof(gw_out.buf));
 	return ret;
 }
 
-- 
2.43.0