On Wed, Mar 29, 2023 at 06:03:23PM +0200, Oleg Nesterov wrote: > On 03/29, Arnd Bergmann wrote: > > > > On Wed, Mar 29, 2023, at 17:15, Oleg Nesterov wrote: > > > > > > This look as if access_ok() or __access_ok() doesn't depend on task, but > > > this is not true in general. Say, TASK_SIZE_MAX can check is_32bit_task() > > > test_thread_flag(TIF_32BIT...) and this uses "current". > > > > > > Again, we probably do not care, but I don't like the fact task_access_ok() > > > looks as if task_access_ok(task) returns the same result as "task" calling > > > access_ok(). > > > > I think the idea of TASK_SIZE_MAX is that it is a compile-time constant and in fact independent of current, while TASK_SIZE > > takes TIF_32BIT into account. > > Say, arch/loongarch defines TASK_SIZE which depends on test_thread_flag(TIF_32BIT_ADDR) > but it doesn't define TASK_SIZE_MAX, so __access_ok() will use TASK_SIZE. > > Oleg. > I did not notice this at first. Thinking of solutions, I'd originally considered writing a similar change in asm-generic that I made in arm64, but that would have ultimately resulted in "(void) task;" because task appears unused. Now it seems like TASK_SIZE/_MAX seems like a dangerous define combination that hides relevant functionality. Fixing this seeems to naturally want a "TASK_TASK_SIZE(task)" which is... uh... annoying. Not sure how I should proceed here, but this makes me wonder if there are oversights like this elsewhere, as this seems like a pretty easy thing to overlook. ~Gregory
