Re: [tip:efi/core] efibc: Add EFI Bootloader Control module

Compostella, Jeremy
2016-05-02T07:58:17Z

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Matt Fleming <matt@codeblueprint.co.uk> writes:

> On Fri, 29 Apr, at 03:53:39PM, Jeremy Compostella wrote:
>> From ef3a2941769e59b11d1ec36117209dc4c90c7cf9 Mon Sep 17 00:00:00 2001
>> From: Jeremy Compostella <jeremy.compostella@intel.com>
>> Date: Fri, 29 Apr 2016 15:29:59 +0200
>> Subject: [PATCH] efibc: fix excessive stack footprint warning
>>
>> Use dynamic memory allocation instead of stack memory for the entry
>> object.
>>
>> This patch also fixes a potential buffer override.
>>
>> Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
>> ---
>> drivers/firmware/efi/efibc.c | 36 ++++++++++++++++++++++++------------
>> 1 file changed, 24 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/firmware/efi/efibc.c b/drivers/firmware/efi/efibc.c
>> index 2e0c7cc..dd6d1a6 100644
>> --- a/drivers/firmware/efi/efibc.c
>> +++ b/drivers/firmware/efi/efibc.c
>> @@ -17,6 +17,7 @@
>> #include <linux/efi.h>
>> #include <linux/module.h>
>> #include <linux/reboot.h>
>> +#include <linux/slab.h>
>>
>> static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
>> {
>> @@ -28,42 +29,53 @@ static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
>> str16[i] = '\0';
>> }
>>
>> -static void efibc_set_variable(const char *name, const char *value)
>> +static int efibc_set_variable(const char *name, const char *value)
>> {
>> int ret;
>> efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
>> - struct efivar_entry entry;
>> + struct efivar_entry *entry;
>> size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
>>
>> - if (size > sizeof(entry.var.Data))
>> + if (size > sizeof(entry->var.Data)) {
>> pr_err("value is too large");
>> + return -1;
>> + }
>
> This isn't right. The usual return value for this scenario would be
> either -ENOMEM or -EINVAL. Personally I'd lean towards -EINVAL.
Right. Done.

>>
>> - efibc_str_to_str16(name, entry.var.VariableName);
>> - efibc_str_to_str16(value, (efi_char16_t *)entry.var.Data);
>> - memcpy(&entry.var.VendorGuid, &guid, sizeof(guid));
>> + entry = kmalloc(sizeof(*entry), GFP_KERNEL);
>> + if (!entry) {
>> + pr_err("failed to allocate efivar entry");
>> + return -1;
>> + }
>
> This should be -ENOMEM.
Done.

>>
>> - ret = efivar_entry_set(&entry,
>> + efibc_str_to_str16(name, entry->var.VariableName);
>> + efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
>> + memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
>> +
>> + ret = efivar_entry_set(entry,
>> EFI_VARIABLE_NON_VOLATILE
>> | EFI_VARIABLE_BOOTSERVICE_ACCESS
>> | EFI_VARIABLE_RUNTIME_ACCESS,
>> - size, entry.var.Data, NULL);
>> + size, entry->var.Data, NULL);
>> if (ret)
>> pr_err("failed to set %s EFI variable: 0x%x\n",
>> name, ret);
>> +
>> + kfree(entry);
>> + return ret;
>> }
>>
>> static int efibc_reboot_notifier_call(struct notifier_block *notifier,
>> unsigned long event, void *data)
>> {
>> const char *reason = "shutdown";
>> + int ret;
>>
>> if (event == SYS_RESTART)
>> reason = "reboot";
>>
>> - efibc_set_variable("LoaderEntryRebootReason", reason);
>> -
>> - if (!data)
>> - return NOTIFY_DONE;
>> + ret = efibc_set_variable("LoaderEntryRebootReason", reason);
>> + if (ret || !data)
>> + return NOTIFY_DONE;
>>
>> efibc_set_variable("LoaderEntryOneShot", (char *)data);
>
> You need to check this return value too now.
We are leaving this function returning NOTIFY_DONE whatever the return
value of that last efibc_set_variable() call.

Please find the updated patch in attachment.

Also, thank you for answering Ard's questions. I promised I won't
look at my emails on Labor day ;)

Jérémy

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>From e50a50dce0762edbc63f15d951b43b21fa7ca784 Mon Sep 17 00:00:00 2001
From: Jeremy Compostella <jeremy.compostella@intel.com>
Date: Fri, 29 Apr 2016 15:29:59 +0200
Subject: [PATCH] efibc: fix excessive stack footprint warning

Use dynamic memory allocation instead of stack memory for the entry
object.

This patch also fixes a potential buffer override.

Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
---
drivers/firmware/efi/efibc.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/firmware/efi/efibc.c b/drivers/firmware/efi/efibc.c
index 2e0c7cc..cb4f573 100644
--- a/drivers/firmware/efi/efibc.c
+++ b/drivers/firmware/efi/efibc.c
@@ -17,6 +17,7 @@
#include <linux/efi.h>
#include <linux/module.h>
#include <linux/reboot.h>
+#include <linux/slab.h>

static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
{
@@ -28,42 +29,53 @@ static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
str16[i] = '\0';
}

-static void efibc_set_variable(const char *name, const char *value)
+static int efibc_set_variable(const char *name, const char *value)
{
int ret;
efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
- struct efivar_entry entry;
+ struct efivar_entry *entry;
size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);

- if (size > sizeof(entry.var.Data))
+ if (size > sizeof(entry->var.Data)) {
pr_err("value is too large");
+ return -EINVAL;
+ }

- efibc_str_to_str16(name, entry.var.VariableName);
- efibc_str_to_str16(value, (efi_char16_t *)entry.var.Data);
- memcpy(&entry.var.VendorGuid, &guid, sizeof(guid));
+ entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ pr_err("failed to allocate efivar entry");
+ return -ENOMEM;
+ }

- ret = efivar_entry_set(&entry,
+ efibc_str_to_str16(name, entry->var.VariableName);
+ efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
+ memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
+
+ ret = efivar_entry_set(entry,
EFI_VARIABLE_NON_VOLATILE
| EFI_VARIABLE_BOOTSERVICE_ACCESS
| EFI_VARIABLE_RUNTIME_ACCESS,
- size, entry.var.Data, NULL);
+ size, entry->var.Data, NULL);
if (ret)
pr_err("failed to set %s EFI variable: 0x%x\n",
name, ret);
+
+ kfree(entry);
+ return ret;
}

static int efibc_reboot_notifier_call(struct notifier_block *notifier,
unsigned long event, void *data)
{
const char *reason = "shutdown";
+ int ret;

if (event == SYS_RESTART)
reason = "reboot";

- efibc_set_variable("LoaderEntryRebootReason", reason);
-
- if (!data)
- return NOTIFY_DONE;
+ ret = efibc_set_variable("LoaderEntryRebootReason", reason);
+ if (ret || !data)
+ return NOTIFY_DONE;

efibc_set_variable("LoaderEntryOneShot", (char *)data);

--
1.9.1

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