pstore: Fix NULL pointer dereference in console writes

Passing a NULL id causes a NULL pointer deference in writers such as
erst_writer and efi_pstore_write because they expect to update this id.
Pass a dummy id instead.

This avoids a cascade of oopses caused when the initial
pstore_console_write passes a null which in turn causes writes to the
console causing further oopses in subsequent pstore_console_write calls.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

fs/pstore/platform.c

@@ -161,6 +161,7 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 
 	while (s < e) {
 		unsigned long flags;
+		u64 id;
 
 		if (c > psinfo->bufsize)
 			c = psinfo->bufsize;
@@ -172,7 +173,7 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 			spin_lock_irqsave(&psinfo->buf_lock, flags);
 		}
 		memcpy(psinfo->buf, s, c);
-		psinfo->write(PSTORE_TYPE_CONSOLE, 0, NULL, 0, c, psinfo);
+		psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, c, psinfo);
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 		s += c;
 		c = e - s;