Re: [PATCH v5 1/2] module: verify address is read-only

[Kees Cook]

On Thu, Apr 6, 2017 at 6:58 PM, Jessica Yu  wrote:
> +++ Eddie Kovsky [05/04/17 21:35 -0600]:
>>
>> Implement a mechanism to check if a module's address is in
>> the rodata or ro_after_init sections. It mimics the existing functions
>> that test if an address is inside a module's text section.
>>
>> Functions that take a module as an argument will be able to verify that
>> the
>> module address is in a read-only section. The idea is to prevent
>> structures
>> (including modules) that are not read-only from being passed to functions.
>>
>> This implements the first half of a suggestion made by Kees Cook for
>> the Kernel Self Protection Project:
>>
>>- provide mechanism to check for ro_after_init memory areas, and
>>  reject structures not marked ro_after_init in vmbus_register()
>>
>> Suggested-by: Kees Cook 
>> Signed-off-by: Eddie Kovsky 
>
>
> Acked-by: Jessica Yu 

Thanks! I'll either get these into my kspp tree or ask akpm to carry
these since they depend on the renaming in his tree already.

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCH v5 1/2] module: verify address is read-only

[Kees Cook]

On Thu, Apr 6, 2017 at 6:58 PM, Jessica Yu  wrote:
> +++ Eddie Kovsky [05/04/17 21:35 -0600]:
>>
>> Implement a mechanism to check if a module's address is in
>> the rodata or ro_after_init sections. It mimics the existing functions
>> that test if an address is inside a module's text section.
>>
>> Functions that take a module as an argument will be able to verify that
>> the
>> module address is in a read-only section. The idea is to prevent
>> structures
>> (including modules) that are not read-only from being passed to functions.
>>
>> This implements the first half of a suggestion made by Kees Cook for
>> the Kernel Self Protection Project:
>>
>>- provide mechanism to check for ro_after_init memory areas, and
>>  reject structures not marked ro_after_init in vmbus_register()
>>
>> Suggested-by: Kees Cook 
>> Signed-off-by: Eddie Kovsky 
>
>
> Acked-by: Jessica Yu 

Thanks! I'll either get these into my kspp tree or ask akpm to carry
these since they depend on the renaming in his tree already.

-Kees

-- 
Kees Cook
Pixel Security

Re: [PATCH v5 1/2] module: verify address is read-only

[Jessica Yu]

+++ Eddie Kovsky [05/04/17 21:35 -0600]:

Implement a mechanism to check if a module's address is in
the rodata or ro_after_init sections. It mimics the existing functions
that test if an address is inside a module's text section.

Functions that take a module as an argument will be able to verify that the
module address is in a read-only section. The idea is to prevent structures
(including modules) that are not read-only from being passed to functions.

This implements the first half of a suggestion made by Kees Cook for
the Kernel Self Protection Project:

   - provide mechanism to check for ro_after_init memory areas, and
 reject structures not marked ro_after_init in vmbus_register()

Suggested-by: Kees Cook 
Signed-off-by: Eddie Kovsky 


Acked-by: Jessica Yu 

Re: [PATCH v5 1/2] module: verify address is read-only

[Jessica Yu]

+++ Eddie Kovsky [05/04/17 21:35 -0600]:

Implement a mechanism to check if a module's address is in
the rodata or ro_after_init sections. It mimics the existing functions
that test if an address is inside a module's text section.

Functions that take a module as an argument will be able to verify that the
module address is in a read-only section. The idea is to prevent structures
(including modules) that are not read-only from being passed to functions.

This implements the first half of a suggestion made by Kees Cook for
the Kernel Self Protection Project:

   - provide mechanism to check for ro_after_init memory areas, and
 reject structures not marked ro_after_init in vmbus_register()

Suggested-by: Kees Cook 
Signed-off-by: Eddie Kovsky 


Acked-by: Jessica Yu 

[PATCH v5 1/2] module: verify address is read-only

[Eddie Kovsky]

Implement a mechanism to check if a module's address is in
the rodata or ro_after_init sections. It mimics the existing functions
that test if an address is inside a module's text section.

Functions that take a module as an argument will be able to verify that the
module address is in a read-only section. The idea is to prevent structures
(including modules) that are not read-only from being passed to functions.

This implements the first half of a suggestion made by Kees Cook for
the Kernel Self Protection Project:

- provide mechanism to check for ro_after_init memory areas, and
  reject structures not marked ro_after_init in vmbus_register()

Suggested-by: Kees Cook 
Signed-off-by: Eddie Kovsky 
---
Changes in v4:
 - Rename function __module_ro_address() to __module_rodata_address()
 - Move module_rodata_address() stub below is_module_address()
 - Minor comment fixes
 - Verify that mod is not NULL before setting up layout variables
Changes in v3:
 - Change function name is_module_ro_address() to
is_module_rodata_address().
 - Improve comments on is_module_rodata_address().
 - Add a !CONFIG_MODULES stub for is_module_rodata_address.
 - Correct and simplify the check for the read-only memory regions in
the module address.
---
 include/linux/module.h | 12 
 kernel/module.c| 53 ++
 2 files changed, 65 insertions(+)

diff --git a/include/linux/module.h b/include/linux/module.h
index 9ad68561d8c2..a3d17b081de3 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -492,7 +492,9 @@ static inline int module_is_live(struct module *mod)
 
 struct module *__module_text_address(unsigned long addr);
 struct module *__module_address(unsigned long addr);
+struct module *__module_rodata_address(unsigned long addr);
 bool is_module_address(unsigned long addr);
+bool is_module_rodata_address(unsigned long addr);
 bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr);
 bool is_module_percpu_address(unsigned long addr);
 bool is_module_text_address(unsigned long addr);
@@ -646,6 +648,11 @@ static inline struct module *__module_address(unsigned 
long addr)
return NULL;
 }
 
+static inline struct module *__module_rodata_address(unsigned long addr)
+{
+   return NULL;
+}
+
 static inline struct module *__module_text_address(unsigned long addr)
 {
return NULL;
@@ -656,6 +663,11 @@ static inline bool is_module_address(unsigned long addr)
return false;
 }
 
+static inline bool is_module_rodata_address(unsigned long addr)
+{
+   return false;
+}
+
 static inline bool is_module_percpu_address(unsigned long addr)
 {
return false;
diff --git a/kernel/module.c b/kernel/module.c
index f953df992a11..d5753210cf34 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -4296,6 +4296,59 @@ struct module *__module_text_address(unsigned long addr)
 }
 EXPORT_SYMBOL_GPL(__module_text_address);
 
+/**
+ * is_module_rodata_address - is this address inside read-only module data?
+ * @addr: the address to check.
+ *
+ */
+bool is_module_rodata_address(unsigned long addr)
+{
+   bool ret;
+
+   preempt_disable();
+   ret = __module_rodata_address(addr) != NULL;
+   preempt_enable();
+
+   return ret;
+}
+
+/*
+ * __module_rodata_address - get the module whose rodata/ro_after_init sections
+ * contain the given address.
+ * @addr: the address.
+ *
+ * Must be called with preempt disabled or module mutex held so that
+ * module doesn't get freed during this.
+ */
+struct module *__module_rodata_address(unsigned long addr)
+{
+   struct module *mod = __module_address(addr);
+
+   /*
+* Make sure module is within the read-only section.
+* range(base + text_size, base + ro_after_init_size)
+* encompasses both the rodata and ro_after_init regions.
+* See comment above frob_text() for the layout diagram.
+*/
+   if (mod) {
+   void *init_base = mod->init_layout.base;
+   unsigned int init_text_size = mod->init_layout.text_size;
+   unsigned int init_ro_after_init_size = 
mod->init_layout.ro_after_init_size;
+
+   void *core_base = mod->core_layout.base;
+   unsigned int core_text_size = mod->core_layout.text_size;
+   unsigned int core_ro_after_init_size = 
mod->core_layout.ro_after_init_size;
+
+   if (!within(addr, init_base + init_text_size,
+   init_ro_after_init_size - init_text_size)
+   && !within(addr, core_base + core_text_size,
+  core_ro_after_init_size - core_text_size))
+   mod = NULL;
+   }
+   return mod;
+}
+EXPORT_SYMBOL_GPL(__module_rodata_address);
+
 /* Don't grab lock, we're oopsing. */
 void print_modules(void)
 {
-- 
2.12.2

[PATCH v5 1/2] module: verify address is read-only

[Eddie Kovsky]

Implement a mechanism to check if a module's address is in
the rodata or ro_after_init sections. It mimics the existing functions
that test if an address is inside a module's text section.

Functions that take a module as an argument will be able to verify that the
module address is in a read-only section. The idea is to prevent structures
(including modules) that are not read-only from being passed to functions.

This implements the first half of a suggestion made by Kees Cook for
the Kernel Self Protection Project:

- provide mechanism to check for ro_after_init memory areas, and
  reject structures not marked ro_after_init in vmbus_register()

Suggested-by: Kees Cook 
Signed-off-by: Eddie Kovsky 
---
Changes in v4:
 - Rename function __module_ro_address() to __module_rodata_address()
 - Move module_rodata_address() stub below is_module_address()
 - Minor comment fixes
 - Verify that mod is not NULL before setting up layout variables
Changes in v3:
 - Change function name is_module_ro_address() to
is_module_rodata_address().
 - Improve comments on is_module_rodata_address().
 - Add a !CONFIG_MODULES stub for is_module_rodata_address.
 - Correct and simplify the check for the read-only memory regions in
the module address.
---
 include/linux/module.h | 12 
 kernel/module.c| 53 ++
 2 files changed, 65 insertions(+)

diff --git a/include/linux/module.h b/include/linux/module.h
index 9ad68561d8c2..a3d17b081de3 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -492,7 +492,9 @@ static inline int module_is_live(struct module *mod)
 
 struct module *__module_text_address(unsigned long addr);
 struct module *__module_address(unsigned long addr);
+struct module *__module_rodata_address(unsigned long addr);
 bool is_module_address(unsigned long addr);
+bool is_module_rodata_address(unsigned long addr);
 bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr);
 bool is_module_percpu_address(unsigned long addr);
 bool is_module_text_address(unsigned long addr);
@@ -646,6 +648,11 @@ static inline struct module *__module_address(unsigned 
long addr)
return NULL;
 }
 
+static inline struct module *__module_rodata_address(unsigned long addr)
+{
+   return NULL;
+}
+
 static inline struct module *__module_text_address(unsigned long addr)
 {
return NULL;
@@ -656,6 +663,11 @@ static inline bool is_module_address(unsigned long addr)
return false;
 }
 
+static inline bool is_module_rodata_address(unsigned long addr)
+{
+   return false;
+}
+
 static inline bool is_module_percpu_address(unsigned long addr)
 {
return false;
diff --git a/kernel/module.c b/kernel/module.c
index f953df992a11..d5753210cf34 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -4296,6 +4296,59 @@ struct module *__module_text_address(unsigned long addr)
 }
 EXPORT_SYMBOL_GPL(__module_text_address);
 
+/**
+ * is_module_rodata_address - is this address inside read-only module data?
+ * @addr: the address to check.
+ *
+ */
+bool is_module_rodata_address(unsigned long addr)
+{
+   bool ret;
+
+   preempt_disable();
+   ret = __module_rodata_address(addr) != NULL;
+   preempt_enable();
+
+   return ret;
+}
+
+/*
+ * __module_rodata_address - get the module whose rodata/ro_after_init sections
+ * contain the given address.
+ * @addr: the address.
+ *
+ * Must be called with preempt disabled or module mutex held so that
+ * module doesn't get freed during this.
+ */
+struct module *__module_rodata_address(unsigned long addr)
+{
+   struct module *mod = __module_address(addr);
+
+   /*
+* Make sure module is within the read-only section.
+* range(base + text_size, base + ro_after_init_size)
+* encompasses both the rodata and ro_after_init regions.
+* See comment above frob_text() for the layout diagram.
+*/
+   if (mod) {
+   void *init_base = mod->init_layout.base;
+   unsigned int init_text_size = mod->init_layout.text_size;
+   unsigned int init_ro_after_init_size = 
mod->init_layout.ro_after_init_size;
+
+   void *core_base = mod->core_layout.base;
+   unsigned int core_text_size = mod->core_layout.text_size;
+   unsigned int core_ro_after_init_size = 
mod->core_layout.ro_after_init_size;
+
+   if (!within(addr, init_base + init_text_size,
+   init_ro_after_init_size - init_text_size)
+   && !within(addr, core_base + core_text_size,
+  core_ro_after_init_size - core_text_size))
+   mod = NULL;
+   }
+   return mod;
+}
+EXPORT_SYMBOL_GPL(__module_rodata_address);
+
 /* Don't grab lock, we're oopsing. */
 void print_modules(void)
 {
-- 
2.12.2