linux-kernel - Re: [GIT PULL] x86 fixes for 3.9

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Date:	Fri, 26 Apr 2013 09:49:36 +0100
From:	Matt Fleming <matt.fleming@...el.com>
To:	Michel Lespinasse <walken@...gle.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...e.hu>,
	Josh Boyer <jwboyer@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Paul Bolle <pebolle@...cali.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [GIT PULL] x86 fixes for 3.9

On 26/04/13 08:43, Michel Lespinasse wrote:
> Still seeing the crash.
> 
> I went and compared the crash dump with the vmlinux disassembly; the
> issue is a NULL pointer dereference in list_for_each_entry_safe().
> list_empty() checks that the head node points to itself, but here the
> head node has NULL. I think this may be due to gsmi_init() being
> called before efivars_init(). Not sure what's the proper fix though.

Ohh... I see what you mean. The bug is in variable_is_present() because
it accesses __efivars directly, which a) isn't the struct efivars gsmi.c
uses and b) hasn't been initialised. Something like this might work.

---

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 182ce94..f4baa11 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -1628,10 +1628,11 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 	return count;
 }
 
-static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor)
+static bool variable_is_present(struct efivars *efivars,
+				efi_char16_t *variable_name,
+				efi_guid_t *vendor)
 {
 	struct efivar_entry *entry, *n;
-	struct efivars *efivars = &__efivars;
 	unsigned long strsize1, strsize2;
 	bool found = false;
 
@@ -1703,8 +1704,8 @@ static void efivar_update_sysfs_entries(struct work_struct *work)
 			if (status != EFI_SUCCESS) {
 				break;
 			} else {
-				if (!variable_is_present(variable_name,
-				    &vendor)) {
+				if (!variable_is_present(efivars,
+				    variable_name, &vendor)) {
 					found = true;
 					break;
 				}
@@ -2008,7 +2009,8 @@ int register_efivars(struct efivars *efivars,
 			 * we'll ever see a different variable name,
 			 * and may end up looping here forever.
 			 */
-			if (variable_is_present(variable_name, &vendor_guid)) {
+			if (variable_is_present(efivars, variable_name,
+						&vendor_guid)) {
 				dup_variable_bug(variable_name, &vendor_guid,
 						 variable_name_size);
 				status = EFI_NOT_FOUND;
--
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