Re: [PATCH] crypto: ecc: handle unaligned input buffer in ecc_swap_digits

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On 7/21/21 4:39 AM, Mian Yousaf Kaukab wrote:
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@xxxxxxx>
Suggested-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@xxxxxxx>


Tested-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>


---
  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]);
  }
/**



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