Re: [PATCH v2 1/2] mm/process_vm_access: pidfd and nowait support for process_vm_readv/writev

[David Hildenbrand (Arm)]

On 4/23/26 16:04, David Laight wrote:
> On Thu, 23 Apr 2026 14:52:26 +0200
> "David Hildenbrand (Arm)" <david@xxxxxxxxxx> wrote:
> 
>>>
>>> pidfd_get_task() returns ERR_PTR() on failure (e.g. ERR_PTR(-EBADF)),
>>> but the code checks "if (!task)" which only catches NULL. An invalid
>>> pidfd will cause mm_access() and put_task_struct() to dereference an
>>> error pointer, crashing the kernel.  
>>
>> Yes. Should we add proper selftests that exercise these code paths?
>>

Just to clarify: I meant adding more tests to patch #2 that trigger the issue here.

> 
> Probably worth checking what happens when a 64bit process tries to
> read high addresses of a 32bit process.
> 

I guess these are a bit harder to write, but would certainly be useful.

-- 
Cheers,

David