On Fri, 2013-03-01 at 11:20 +0800, Lee, Chun-Yi wrote:
> From: Michael Schroeder <m...@suse.com>
>
> On HP z220 system (firmware version 1.54), some EFI variables are incorrectly
> named :
>
> ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns
> /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c
>
> That causes by the following statement in efivar_create_sysfs_entry function:
>
> *(short_name + strlen(short_name)) = '-';
> efi_guid_unparse(vendor_guid, short_name + strlen(short_name));
>
> The trailing \0 is overwritten with '-', but the next char doesn't seem to be
> a \0
> as well for HP. So, the second strlen return the point of next '\0', causes
> there
> have garbage string attached before GUID.
>
> Tested on On HP z220.
What's more likely happening here is that GetNextVariable() is broken on
this HP firmware and variable_name_size is too big for the given
variable in variable_name. We've seen other reports of similar bugs,
https://bugzilla.kernel.org/show_bug.cgi?id=47631
Could someone try this patch against Linus' tree?
---
>From fe38d6f69c889b0f95c5548c724633aa58c2c99f Mon Sep 17 00:00:00 2001
From: Matt Fleming <matt.flem...@intel.com>
Date: Fri, 1 Mar 2013 14:49:12 +0000
Subject: [PATCH] efivars: Sanitise string length returned by
GetNextVariableName()
Some buggy firmware implementations return a string length from
GetNextVariableName() that is actually larger than the string in
'variable_name', as Michael Schroeder writes,
> On HP z220 system (firmware version 1.54), some EFI variables are
> incorrectly named :
>
> ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns
> /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
>
/sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c
Since 'variable_name' is a string, we can validate its size by
searching for the terminating NULL character.
Reported-by: Frederic Crozat <fcro...@suse.com>
Cc: Matthew Garrett <mj...@srcf.ucam.org>
Cc: Josh Boyer <jwbo...@redhat.com>
Cc: Michael Schroeder <m...@suse.com>
Cc: Lee, Chun-Yi <j...@suse.com>
Cc: Lingzhu Xiang <lxi...@redhat.com>
Signed-off-by: Matt Fleming <matt.flem...@intel.com>
---
drivers/firmware/efivars.c | 35 ++++++++++++++++++++++++++++++++++-
1 file changed, 34 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 7320bf8..b5af292 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -1653,6 +1653,33 @@ static bool variable_is_present(efi_char16_t
*variable_name, efi_guid_t *vendor)
return found;
}
+/*
+ * Sanity check string length of a variable name.
+ */
+static unsigned long sanity_check_strlen(efi_char16_t *variable_name,
+ unsigned long variable_name_size)
+{
+ efi_char16_t c;
+ unsigned long len;
+
+ /*
+ * The variable name is, by definition, a NULL-terminated
+ * string, so make absolutely sure that variable_name_size is
+ * the value we expect it to be. If not, use whichever size is
+ * smaller.
+ */
+ for (len = 1; len <= variable_name_size; len++) {
+ c = variable_name[len - 1];
+ if (!c)
+ break;
+ }
+
+ if (len != variable_name_size)
+ printk(KERN_WARNING "efivars: bogus variable_name_size\n");
+
+ return min(len, variable_name_size);
+}
+
static void efivar_update_sysfs_entries(struct work_struct *work)
{
struct efivars *efivars = &__efivars;
@@ -1693,10 +1720,13 @@ static void efivar_update_sysfs_entries(struct
work_struct *work)
if (!found) {
kfree(variable_name);
break;
- } else
+ } else {
+ variable_name_size = sanity_check_strlen(variable_name,
+
variable_name_size);
efivar_create_sysfs_entry(efivars,
variable_name_size,
variable_name, &vendor);
+ }
}
}
@@ -1941,8 +1971,11 @@ int register_efivars(struct efivars *efivars,
status = ops->get_next_variable(&variable_name_size,
variable_name,
&vendor_guid);
+
switch (status) {
case EFI_SUCCESS:
+ variable_name_size = sanity_check_strlen(variable_name,
+
variable_name_size);
efivar_create_sysfs_entry(efivars,
variable_name_size,
variable_name,
--
1.7.11.7
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