ACPI: APEI / ERST: Fix missing error handling in erst_reader()

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)
Cc: All applicable <stable@vger.kernel.org>
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>

diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
index 6742f6c68034c5e833505d294902dd97c274c1b0..9bff853e85f37831d8d053a2aa363f139537c9b5 100644 (file)
--- a/drivers/acpi/apei/erst.c
+++ b/drivers/acpi/apei/erst.c
@@ -1007,7 +1007,7 @@ skip:
        /* The record may be cleared by others, try read next record */
        if (len == -ENOENT)
                goto skip;
-       else if (len < sizeof(*rcd)) {
+       else if (len < 0 || len < sizeof(*rcd)) {
                rc = -EIO;
                goto out;
        }