On Fri, 2013-03-01 at 15:17 +0000, Matt Fleming wrote:
> 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?
Urgh, and here's a version that isn't utterly, utterly broken...
---
>From 4b2ef72bca72039717efe4570ec858a86d565b34 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 | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 7320bf8..ab477b8 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -1895,6 +1895,33 @@ void unregister_efivars(struct efivars *efivars)
}
EXPORT_SYMBOL_GPL(unregister_efivars);
+/*
+ * Sanity check size of a variable name.
+ */
+static unsigned long sanity_check_size(efi_char16_t *variable_name,
+ unsigned long variable_name_size)
+{
+ unsigned long len;
+ efi_char16_t c;
+
+ /*
+ * 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, return the real size.
+ */
+ for (len = 2; len <= variable_name_size; len += sizeof(c)) {
+ c = variable_name[(len / sizeof(c)) - 1];
+ if (!c)
+ break;
+ }
+
+
+ if (len != variable_name_size)
+ printk(KERN_WARNING "efivars: bogus variable_name_size: %lu
%lu\n", len, variable_name_size);
+
+ return min(len, variable_name_size);
+}
+
int register_efivars(struct efivars *efivars,
const struct efivar_operations *ops,
struct kobject *parent_kobj)
@@ -1941,8 +1968,11 @@ 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_size(variable_name,
+
variable_name_size);
efivar_create_sysfs_entry(efivars,
variable_name_size,
variable_name,
--
1.7.11.7
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