lkml.org 
[lkml]   [2022]   [Aug]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[bug report] mm, hwpoison: memory_failure races with alloc_fresh_huge_page/free_huge_page
Date
Hi all:
When I investigate the mm/memory-failure.c code again, I found there's a possible race window
between memory_failure and alloc_fresh_huge_page/free_huge_page. Thank about the below scene:

CPU 1 CPU 2
alloc_fresh_huge_page -- page refcnt > 0 memory_failure
prep_new_huge_page get_huge_page_for_hwpoison
!PageHeadHuge -- so 2(not a hugepage) is returned
hugetlb_vmemmap_optimize -- subpages is read-only
set_compound_page_dtor -- PageHuge is true now, but too late!!!
TestSetPageHWPoison(p)
-- We might write to read-only subpages here!!!

Another similar scene:

CPU 1 CPU 2
free_huge_page -- page refcnt == 0 and not PageHuge memory_failure
get_huge_page_for_hwpoison
!PageHeadHuge -- so 2(not a hugepage) is returned
TestSetPageHWPoison(p)
-- We might write to read-only subpages here!!!
hugetlb_vmemmap_restore -- subpages can be written to now, but too late!!!

I think the above scenes are possible. But I can't found a stable solution to fix it. Any suggestions?
Or is it not worth to fix it as it's too rare? Or am I miss something?

Any response would be appreciated!

Thanks!

\
 
 \ /
  Last update: 2022-08-02 04:02    [W:0.097 / U:5.900 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site