linux-kernel - [PATCH] crypto: ecc: handle unaligned input buffer in ecc_swap

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Date:   Wed, 21 Jul 2021 10:39:05 +0200
From:   Mian Yousaf Kaukab <ykaukab@...e.de>
To:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     stefanb@...ux.ibm.com, davem@...emloft.net,
        herbert@...dor.apana.org.au, tiwai@...e.de,
        guillaume.gardet@....com, Mian Yousaf Kaukab <ykaukab@...e.de>
Subject: [PATCH] crypto: ecc: handle unaligned input buffer in ecc_swap_digits

ecdsa_set_pub_key() makes an u64 pointer at 1 byte offset of the key.
This results in an unaligned u64 pointer. This pointer is passed to
ecc_swap_digits() which assumes natural alignment.

This causes a kernel crash on an armv7 platform:
[    0.409022] Unhandled fault: alignment exception (0x001) at 0xc2a0a6a9
...
[    0.416982] PC is at ecdsa_set_pub_key+0xdc/0x120
...
[    0.491492] Backtrace:
[    0.492059] [<c07c266c>] (ecdsa_set_pub_key) from [<c07c75d4>] (test_akcipher_one+0xf4/0x6c0)

Handle unaligned input buffer in ecc_swap_digits() by replacing
be64_to_cpu() to get_unaligned_be64(). Change type of in pointer to
void to reflect it doesn’t necessarily need to be aligned.

Fixes: 4e6602916bc6 ("crypto: ecdsa - Add support for ECDSA signature verification")
Reported-by: Guillaume Gardet <guillaume.gardet@....com>
Suggested-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@...e.de>
---
 crypto/ecc.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/crypto/ecc.h b/crypto/ecc.h
index a006132646a4..1350e8eb6ac2 100644
--- a/crypto/ecc.h
+++ b/crypto/ecc.h
@@ -27,6 +27,7 @@
 #define _CRYPTO_ECC_H
 
 #include <crypto/ecc_curve.h>
+#include <asm/unaligned.h>
 
 /* One digit is u64 qword. */
 #define ECC_CURVE_NIST_P192_DIGITS  3
@@ -46,13 +47,13 @@
  * @out:      Output array
  * @ndigits:  Number of digits to copy
  */
-static inline void ecc_swap_digits(const u64 *in, u64 *out, unsigned int ndigits)
+static inline void ecc_swap_digits(const void *in, u64 *out, unsigned int ndigits)
 {
 	const __be64 *src = (__force __be64 *)in;
 	int i;
 
 	for (i = 0; i < ndigits; i++)
-		out[i] = be64_to_cpu(src[ndigits - 1 - i]);
+		out[i] = get_unaligned_be64(&src[ndigits - 1 - i]);
 }
 
 /**
-- 
2.26.2