From 8f8a0c9e60213d2ab8ea2520ba79c8d1c58fe60a Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 14 Dec 2017 13:31:16 +0100
Subject: [PATCH] ACPI: APEI / ERST: Fix missing error handling in
 erst_reader()

commit bb82e0b4a7e96494f0c1004ce50cec3d7b5fb3d1 upstream.

The commit f6f828513290 ("pstore: pass allocated memory region back to
caller") changed the check of the return value from erst_read() in
erst_reader() in the following way:

        if (len == -ENOENT)
                goto skip;
-       else if (len < 0) {
-               rc = -1;
+       else if (len < sizeof(*rcd)) {
+               rc = -EIO;
                goto out;

This introduced another bug: since the comparison with sizeof() is
cast to unsigned, a negative len value doesn't hit any longer.
As a result, when an error is returned from erst_read(), the code
falls through, and it may eventually lead to some weird thing like
memory corruption.

This patch adds the negative error value check more explicitly for
addressing the issue.

Fixes: f6f828513290 (pstore: pass allocated memory region back to caller)
Tested-by: Jerry Tang <jtang@suse.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
Reading git-format-patch failed