Re: [PATCH v7 1/7] selftests/proc: add /proc/pid/maps tearing from vma split test

[David Hildenbrand <david@redhat.com>]

On 16.07.25 05:05, Suren Baghdasaryan wrote:
> The /proc/pid/maps file is generated page by page, with the mmap_lock
> released between pages.  This can lead to inconsistent reads if the
> underlying vmas are concurrently modified. For instance, if a vma split
> or merge occurs at a page boundary while /proc/pid/maps is being read,
> the same vma might be seen twice: once before and once after the change.
> This duplication is considered acceptable for userspace handling.
> However, observing a "hole" where a vma should be (e.g., due to a vma
> being replaced and the space temporarily being empty) is unacceptable.
> 
> Implement a test that:
> 1. Forks a child process which continuously modifies its address space,
> specifically targeting a vma at the boundary between two pages.
> 2. The parent process repeatedly reads the child's /proc/pid/maps.
> 3. The parent process checks the last vma of the first page and
> the first vma of the second page for consistency, looking for the
> effects of vma splits or merges.
> 
> The test duration is configurable via the -d command-line parameter
> in seconds to increase the likelihood of catching the race condition.
> The default test duration is 5 seconds.
> 
> Example Command: proc-maps-race -d 10
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>

Why is this selftest not making use of any kselftest framework?

I'm sure there is a very good reason :)

Reading assert() feels very weird compared to other selftests.

-- 
Cheers,

David / dhildenb