TononixOS/ubports_kernel_google_msm
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mm: PageBuddy and mapcount robustness

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Change the _mapcount value indicating PageBuddy from -2 to -128 for
more robusteness against page_mapcount() undeflows.

Use reset_page_mapcount instead of __ClearPageBuddy in bad_page to
ignore the previous retval of PageBuddy().

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli
2011-03-18 00:16:35 +01:00
committed by Linus Torvalds
parent 7b7adc4a01
commit ef2b4b95a6
2 changed files with 11 additions and 4 deletions
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4
mm/page_alloc.c
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@@ -286,7 +286,7 @@ static void bad_page(struct page *page)
/* Don't complain about poisoned pages */
if (PageHWPoison(page)) {
__ClearPageBuddy(page);
reset_page_mapcount(page); /* remove PageBuddy */
return;
}
@@ -317,7 +317,7 @@ static void bad_page(struct page *page)
dump_stack();
out:
/* Leave bad fields for debug, except PageBuddy could make trouble */
__ClearPageBuddy(page);
reset_page_mapcount(page); /* remove PageBuddy */
add_taint(TAINT_BAD_PAGE);
}