efi/cper: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().

Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/[email protected]

Author: tiwai

drivers/firmware/efi/cper.c

@@ -101,7 +101,7 @@ void cper_print_bits(const char *pfx, unsigned int bits,
 		if (!len)
 			len = snprintf(buf, sizeof(buf), "%s%s", pfx, str);
 		else
-			len += snprintf(buf+len, sizeof(buf)-len, ", %s", str);
+			len += scnprintf(buf+len, sizeof(buf)-len, ", %s", str);
 	}
 	if (len)
 		printk("%s\n", buf);