[PATCH u-boot v2019.04-aspeed-openbmc] as2600/scu: Fix printing of security info

[Joel Stanley]

The current code misses initialising the char buffer 'alg' to zero,
causing the sprintf to potentially write past the end of the buffer.

Most of the time strlen happened upon a 0 early in the buffer, and the
resulting string would be constructed in bounds:

 Secure Boot: Mode_2, m��ERSA4096_SHA512

Avoid the issue by not constructing the string in memory. Instead print
it out as the bits are parsed.

Fixes: dd27b24b13d5 ("ARM: Aspeed: update secure boot information")
Signed-off-by: Joel Stanley <joel at jms.id.au>
---
 arch/arm/mach-aspeed/ast2600/scu_info.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/arm/mach-aspeed/ast2600/scu_info.c b/arch/arm/mach-aspeed/ast2600/scu_info.c
index 606b2445e7de..a2277eec584d 100644
--- a/arch/arm/mach-aspeed/ast2600/scu_info.c
+++ b/arch/arm/mach-aspeed/ast2600/scu_info.c
@@ -95,7 +95,6 @@ void aspeed_print_security_info(void)
 	u32 sb_sts = readl(ASPEED_SB_STS);
 	u32 hash;
 	u32 rsa;
-	char alg[20];
 
 	if (!(sb_sts & BIT(6)))
 		return;
@@ -104,38 +103,39 @@ void aspeed_print_security_info(void)
 		hash = (qsr >> 10) & 3;
 		rsa = (qsr >> 12) & 3;
 
+		printf("Mode_2, ");
+
 		if (qsr & BIT(27)) {
-			sprintf(alg + strlen(alg), "AES_");
+			printf("AES_");
 		}
 		switch (rsa) {
 		case 0:
-			sprintf(alg + strlen(alg), "RSA1024_");
+			printf("RSA1024_");
 			break;
 		case 1:
-			sprintf(alg + strlen(alg), "RSA2048_");
+			printf("RSA2048_");
 			break;
 		case 2:
-			sprintf(alg + strlen(alg), "RSA3072_");
+			printf("RSA3072_");
 			break;
 		default:
-			sprintf(alg + strlen(alg), "RSA4096_");
+			printf("RSA4096_");
 			break;
 		}
 		switch (hash) {
 		case 0:
-			sprintf(alg + strlen(alg), "SHA224");
+			printf("SHA224\n");
 			break;
 		case 1:
-			sprintf(alg + strlen(alg), "SHA256");
+			printf("SHA256\n");
 			break;
 		case 2:
-			sprintf(alg + strlen(alg), "SHA384");
+			printf("SHA384\n");
 			break;
 		default:
-			sprintf(alg + strlen(alg), "SHA512");
+			printf("SHA512\n");
 			break;
 		}
-		printf("Mode_2, %s\n", alg);
 	} else {
 		printf("Mode_GCM\n");
 		return;
-- 
2.34.1