On Thu, May 25, 2017 at 10:46 AM, Luis R. Rodriguez <mcg...@kernel.org> wrote:
> On Thu, May 25, 2017 at 10:57:51AM +0200, Thomas Gleixner wrote:
>> ftrace use module_alloc() to allocate trampoline pages. The mapping of
>> module_alloc() is RWX, which makes sense as the memory is written to right
>> after allocation. But nothing makes these pages RO after writing to them.
>>
>> Add proper set_memory_rw/ro() calls to protect the trampolines after
>> modification.
>>
>> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
>> ---
>> arch/x86/kernel/ftrace.c | 20 ++++++++++++++------
>> 1 file changed, 14 insertions(+), 6 deletions(-)
>>
>> --- a/arch/x86/kernel/ftrace.c
>> +++ b/arch/x86/kernel/ftrace.c
>> @@ -689,8 +689,12 @@ static inline void *alloc_tramp(unsigned
>> {
>> return module_alloc(size);
>> }
>> -static inline void tramp_free(void *tramp)
>> +static inline void tramp_free(void *tramp, int size)
>> {
>> + int npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>> +
>> + set_memory_nx((unsigned long)tramp, npages);
>> + set_memory_rw((unsigned long)tramp, npages);
>> module_memfree(tramp);
>> }
>
> Can/should module_memfree() just do this for users? With Masami's fix that'd
> be 2 users already.
It seems like it really should. That would put it in a single place
and avoid this mistake again in the future. Does module_memfree() have
access to the allocation size, or does that need to get plumbed?
-Kees
--
Kees Cook
Pixel Security
