On Fri, May 11, 2018 at 08:18:27PM +0200, Heinrich Schuchardt wrote:

On 05/11/2018 07:54 PM, Ivan Gorinov wrote:

...

efi_get_variable() always stores an extra zero byte after the output data. When the returned data size matches the output buffer size, the extra zero byte is stored past the end of the output buffer.

Signed-off-by: Ivan Gorinov ivan.gorinov@intel.com

lib/efi_loader/efi_variable.c | 40 +++++++++++++++++----------------------- 1 file changed, 17 insertions(+), 23 deletions(-)

diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c index 6c177da..28b2f5c 100644 --- a/lib/efi_loader/efi_variable.c +++ b/lib/efi_loader/efi_variable.c @@ -50,7 +50,7 @@ (strlen("efi_xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxxxxxx_") + \ (MAX_VAR_NAME * MAX_UTF8_PER_UTF16))

-static int hex(unsigned char ch) +static int hex(int ch) { if (ch >= 'a' && ch <= 'f') return ch-'a'+10; @@ -61,44 +61,34 @@ static int hex(unsigned char ch) return -1; }

-static const char *hex2mem(u8 *mem, const char *hexstr, int count) +static int hex2mem(u8 *mem, const char *hexstr, int size) {

• memset(mem, 0, count/2);

• int nibble;
• int i;

• do {

• int nibble;
  

• memset(mem, 0, size);

Why should we call memset?

The memory is supplied by the caller of efi_get_variable(). Either we copy size bytes to mem or we return EFI_DEVICE_ERROR.

OK.

...

• *mem = 0;
  

• if (!count || !*hexstr)
  

• for (i = 0; i < size; i++) {

• if (*hexstr == '\0')
  break;
  
  

  nibble = hex(*hexstr); if (nibble < 0)

• 	break;
  

• 	return -1;
  
  

  *mem = nibble;

• count--;
  

  hexstr++;

• if (!count || !*hexstr)
  

• 	break;
  

• nibble = hex(*hexstr); if (nibble < 0)

• 	break;
  

• 	return -1;
  
  

  *mem = (*mem << 4) | nibble;

• count--;
  

  hexstr++; mem++;

• }

• } while (1);
• if (*hexstr)

• return hexstr;
  

• return NULL;

• return i;

}

static char *mem2hex(char *hexstr, const u8 *mem, int count) @@ -210,8 +200,12 @@ efi_status_t EFIAPI efi_get_variable(s16 *variable_name, if ((s = prefix(val, "(blob)"))) { unsigned len = strlen(s);

• /* number of hexadecimal digits must be even */
  

• if (len & 1)
  

• 	return EFI_EXIT(EFI_DEVICE_ERROR);
  

• /* two characters per byte: */

• len = DIV_ROUND_UP(len, 2);
  

• len /= 2;
  

You do not catch the case that len & 1 == 1 which should cause EFI_DEVICE_ERROR because the data in the blob is not valid.

This is exactly what new code in efi_get_variable() does:

if (len & 1) return EFI_EXIT(EFI_DEVICE_ERROR);

Best regards

Heinrich

...

*data_size = len;

if (in_size < len)

@@ -220,7 +214,7 @@ efi_status_t EFIAPI efi_get_variable(s16 *variable_name, if (!data) return EFI_EXIT(EFI_INVALID_PARAMETER);

• if (hex2mem(data, s, len * 2))
  

• if (hex2mem(data, s, len) != len)
  return EFI_EXIT(EFI_DEVICE_ERROR);
  

Even if we did not check the string length early, hex2mem() would return -1 when the number of digits is odd.

...

debug("%s: got value: \"%s\"\n", __func__, s);