util/cbmem: Fix out of bounds access

Building cbmem with ASan

	$ CC=gcc-5 CFLAGS="-O1 -g -fsanitize=address -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address" make

it sometimes finds a heap-buffer-overflow, while dumping the CBMEM
console.

$ sudo ./cbmem -c
=================================================================
==11208==ERROR: AddressSanitizer: heap-buffer-overflow on address 0xb5d5782b at pc 0x0804a4d7 bp 0xbfe23bc8 sp 0xbfe23bbc
WRITE of size 1 at 0xb5d5782b thread T0
    #0 0x804a4d6 in dump_console /home/joey/src/coreboot/util/cbmem/cbmem.c:553
    #1 0x804a4d6 in main /home/joey/src/coreboot/util/cbmem/cbmem.c:1134
    #2 0xb70a3a62 in __libc_start_main (/lib/i386-linux-gnu/i686/cmov/libc.so.6+0x19a62)
    #3 0x8048cf0  (/home/joey/src/coreboot/util/cbmem/cbmem+0x8048cf0)

0xb5d5782b is located 50 bytes to the right of 131065-byte region [0xb5d37800,0xb5d577f9)
allocated by thread T0 here:
    #0 0xb72c64ce in __interceptor_malloc (/usr/lib/i386-linux-gnu/libasan.so.2+0x924ce)
    #1 0x804a407 in dump_console /home/joey/src/coreboot/util/cbmem/cbmem.c:542
    #2 0x804a407 in main /home/joey/src/coreboot/util/cbmem/cbmem.c:1134
    #3 0xb70a3a62 in __libc_start_main (/lib/i386-linux-gnu/i686/cmov/libc.so.6+0x19a62)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/joey/src/coreboot/util/cbmem/cbmem.c:553 dump_console
Shadow bytes around the buggy address:
  0x36baaeb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x36baaec0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x36baaed0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x36baaee0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x36baaef0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01
=>0x36baaf00: fa fa fa fa fa[fa]fa fa fa fa fa fa fa fa fa fa
  0x36baaf10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x36baaf20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x36baaf30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x36baaf40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x36baaf50: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
==11208==ABORTING

Fix up commit 06b13a37 (cbmem: Terminate the cbmem console at the cursor
position.) by reverting setting the cursor to 0.

Change-Id: Id614a8e0f1a202671dd091f825d826a17176bfcc
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/10572
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/util/cbmem/cbmem.c b/util/cbmem/cbmem.c
index 3c7f49b880..d8c6145732 100644
--- a/util/cbmem/cbmem.c
+++ b/util/cbmem/cbmem.c
@@ -685,7 +685,7 @@ static void dump_console(void)
 	 */
 	if (size > cursor)
 		size = cursor;
-	console_c = malloc(size + 1);
+	console_c = calloc(1, size + 1);
 	unmap_memory();
 	if (!console_c) {
 		fprintf(stderr, "Not enough memory for console.\n");
@@ -695,8 +695,6 @@ static void dump_console(void)
 	console_p = map_memory_size((unsigned long)console.cbmem_addr,
 	                            size + sizeof(size) + sizeof(cursor), 1);
 	memcpy(console_c, console_p + 8, size);
-	console_c[size] = 0;
-	console_c[cursor] = 0;
 
 	printf("%s\n", console_c);
 	if (size < cursor)