[PATCH 2/5] bios32: ensure mmap'd memory is readable before accessing it

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

We need to check we don't get SIGSEGV or SIGBUS errors when reading
the mmap'd data before we try and access it. Use the fwts_safe_memread
check on the data to sanity check these mappings.

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 src/bios/bios32/bios32.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/bios/bios32/bios32.c b/src/bios/bios32/bios32.c
index e7f086f2..330f05e3 100644
--- a/src/bios/bios32/bios32.c
+++ b/src/bios/bios32/bios32.c
@@ -65,6 +65,11 @@ static int bios32_test1(fwts_framework *fw)
 	}
 
 	for (i = 0; i < BIOS32_SD_REGION_SIZE; i+= 16) {
+		const size_t size = sizeof(fwts_bios32_service_directory);
+
+		/* Is the region safe to read? */
+		if (fwts_safe_memread(mem, size) != FWTS_OK)
+			continue;
 		if ((*(mem+i)   == '_') &&
 		    (*(mem+i+1) == '3') &&
 		    (*(mem+i+2) == '2') &&
-- 
2.11.0