Re: [PATCH 09/10] vhost, mm: make sure that oom_reaper doesn't reap memory read by vhost
From: Michal Hocko <mhocko@kernel.org>
Date: 2016-08-15 09:49:15
On Mon 15-08-16 02:06:31, Michael S. Tsirkin wrote: [...]
quoted hunk ↗ jump to hunk
So fundamentally, won't the following make copy to/from user return EFAULT? If yes, vhost is already prepared to handle that.diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index dc80230..e5dbee5 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c@@ -1309,6 +1309,11 @@ retry: might_sleep(); } + if (unlikely(test_bit(MMF_UNSTABLE, &mm->flags))) { + bad_area(regs, error_code, address); + return; + } + vma = find_vma(mm, address); if (unlikely(!vma)) { bad_area(regs, error_code, address);
This would be racy but even if we did the check _after_ the #PF is handled then I am not very happy to touch the #PF path which is quite hot for something as rare as OOM and which only has one user which needs a special handling. That is the primary reason why I prefer the specific API. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>