From: Eric Biggers <ebiggers@kernel.org>
Date: Mon, 20 Apr 2026 06:33:46 +0000 (-0700)
Subject: crypto: drbg - Fix misaligned writes in CTR_DRBG and HASH_DRBG
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=ddc4dedb9ba3c8eecbc8c050fffd46d1b7e75c21;p=thirdparty%2Fkernel%2Flinux.git

crypto: drbg - Fix misaligned writes in CTR_DRBG and HASH_DRBG

drbg_cpu_to_be32() is being used to do a plain write to a byte array,
which doesn't have any alignment guarantee.  This can cause a misaligned
write.  Replace it with the correct function, put_unaligned_be32().

Fixes: 72f3e00dd67e ("crypto: drbg - replace int2byte with cpu_to_be")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

diff --git a/crypto/df_sp80090a.c b/crypto/df_sp80090a.c
index b8134be6f7ad9..f4bb7be016e85 100644
--- a/crypto/df_sp80090a.c
+++ b/crypto/df_sp80090a.c
@@ -10,6 +10,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/string.h>
+#include <linux/unaligned.h>
 #include <crypto/aes.h>
 #include <crypto/df_sp80090a.h>
 #include <crypto/internal/drbg.h>
@@ -141,10 +142,10 @@ int crypto_drbg_ctr_df(struct aes_enckey *aeskey,
 	/* 10.4.2 step 2 -- calculate the entire length of all input data */
 	list_for_each_entry(seed, seedlist, list)
 		inputlen += seed->len;
-	drbg_cpu_to_be32(inputlen, &L_N[0]);
+	put_unaligned_be32(inputlen, &L_N[0]);
 
 	/* 10.4.2 step 3 */
-	drbg_cpu_to_be32(bytes_to_return, &L_N[4]);
+	put_unaligned_be32(bytes_to_return, &L_N[4]);
 
 	/* 10.4.2 step 5: length is L_N, input_string, one byte, padding */
 	padlen = (inputlen + sizeof(L_N) + 1) % (blocklen_bytes);
@@ -175,7 +176,7 @@ int crypto_drbg_ctr_df(struct aes_enckey *aeskey,
 		 * holds zeros after allocation -- even the increment of i
 		 * is irrelevant as the increment remains within length of i
 		 */
-		drbg_cpu_to_be32(i, iv);
+		put_unaligned_be32(i, iv);
 		/* 10.4.2 step 9.2 -- BCC and concatenation with temp */
 		drbg_ctr_bcc(aeskey, temp + templen, K, &bcc_list,
 			     blocklen_bytes, keylen);
diff --git a/crypto/drbg.c b/crypto/drbg.c
index e4eb78ed222b9..de4c69032155e 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -103,6 +103,7 @@
 #include <linux/kernel.h>
 #include <linux/jiffies.h>
 #include <linux/string_choices.h>
+#include <linux/unaligned.h>
 
 /***************************************************************
  * Backend cipher definitions available to DRBG
@@ -601,7 +602,7 @@ static int drbg_hash_df(struct drbg_state *drbg,
 
 	/* 10.4.1 step 3 */
 	input[0] = 1;
-	drbg_cpu_to_be32((outlen * 8), &input[1]);
+	put_unaligned_be32(outlen * 8, &input[1]);
 
 	/* 10.4.1 step 4.1 -- concatenation of data for input into hash */
 	drbg_string_fill(&data, input, 5);
diff --git a/include/crypto/internal/drbg.h b/include/crypto/internal/drbg.h
index 371e52dcee6c5..b4e5ef0be602f 100644
--- a/include/crypto/internal/drbg.h
+++ b/include/crypto/internal/drbg.h
@@ -9,24 +9,6 @@
 #ifndef _INTERNAL_DRBG_H
 #define _INTERNAL_DRBG_H
 
-/*
- * Convert an integer into a byte representation of this integer.
- * The byte representation is big-endian
- *
- * @val value to be converted
- * @buf buffer holding the converted integer -- caller must ensure that
- *      buffer size is at least 32 bit
- */
-static inline void drbg_cpu_to_be32(__u32 val, unsigned char *buf)
-{
-	struct s {
-		__be32 conv;
-	};
-	struct s *conversion = (struct s *)buf;
-
-	conversion->conv = cpu_to_be32(val);
-}
-
 /*
  * Concatenation Helper and string operation helper
  *