From 46d8c4b28652d35dc6cfb5adf7f54e102fc04384 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Fri, 13 Jul 2018 16:12:32 +0800
Subject: [PATCH] crypto: padlock-aes - Fix Nano workaround data corruption
Git-commit: 46d8c4b28652d35dc6cfb5adf7f54e102fc04384
Patch-mainline: v4.18-rc8
References: bsc#1051510

This was detected by the self-test thanks to Ard's chunking patch.

I finally got around to testing this out on my ancient Via box.  It
turns out that the workaround got the assembly wrong and we end up
doing count + initial cycles of the loop instead of just count.

This obviously causes corruption, either by overwriting the source
that is yet to be processed, or writing over the end of the buffer.

On CPUs that don't require the workaround only ECB is affected.
On Nano CPUs both ECB and CBC are affected.

This patch fixes it by doing the subtraction prior to the assembly.

Fixes: a76c1c23d0c3 ("crypto: padlock-aes - work around Nano CPU...")
Cc: <stable@vger.kernel.org>
Reported-by: Jamie Heilman <jamie@audible.transient.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/crypto/padlock-aes.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/padlock-aes.c b/drivers/crypto/padlock-aes.c
index 1c6cbda56afe..09d823d36d3a 100644
--- a/drivers/crypto/padlock-aes.c
+++ b/drivers/crypto/padlock-aes.c
@@ -266,6 +266,8 @@ static inline void padlock_xcrypt_ecb(const u8 *input, u8 *output, void *key,
 		return;
 	}
 
+	count -= initial;
+
 	if (initial)
 		asm volatile (".byte 0xf3,0x0f,0xa7,0xc8"	/* rep xcryptecb */
 			      : "+S"(input), "+D"(output)
@@ -273,7 +275,7 @@ static inline void padlock_xcrypt_ecb(const u8 *input, u8 *output, void *key,
 
 	asm volatile (".byte 0xf3,0x0f,0xa7,0xc8"	/* rep xcryptecb */
 		      : "+S"(input), "+D"(output)
-		      : "d"(control_word), "b"(key), "c"(count - initial));
+		      : "d"(control_word), "b"(key), "c"(count));
 }
 
 static inline u8 *padlock_xcrypt_cbc(const u8 *input, u8 *output, void *key,
@@ -284,6 +286,8 @@ static inline u8 *padlock_xcrypt_cbc(const u8 *input, u8 *output, void *key,
 	if (count < cbc_fetch_blocks)
 		return cbc_crypt(input, output, key, iv, control_word, count);
 
+	count -= initial;
+
 	if (initial)
 		asm volatile (".byte 0xf3,0x0f,0xa7,0xd0"	/* rep xcryptcbc */
 			      : "+S" (input), "+D" (output), "+a" (iv)
@@ -291,7 +295,7 @@ static inline u8 *padlock_xcrypt_cbc(const u8 *input, u8 *output, void *key,
 
 	asm volatile (".byte 0xf3,0x0f,0xa7,0xd0"	/* rep xcryptcbc */
 		      : "+S" (input), "+D" (output), "+a" (iv)
-		      : "d" (control_word), "b" (key), "c" (count-initial));
+		      : "d" (control_word), "b" (key), "c" (count));
 	return iv;
 }
 
-- 
2.18.0