Thread (6 messages) 6 messages, 3 authors, 2023-03-09

Re: [PATCH v3 1/2] Revert "kasan: drop skip_kasan_poison variable in free_pages_prepare"

From: Andrew Morton <akpm@linux-foundation.org>
Date: 2023-03-09 01:46:16
Also in: linux-mm, stable

On Tue, 28 Feb 2023 16:35:44 -0800 Peter Collingbourne [off-list ref] wrote:
This reverts commit 487a32ec24be819e747af8c2ab0d5c515508086a.

The should_skip_kasan_poison() function reads the PG_skip_kasan_poison
flag from page->flags. However, this line of code in free_pages_prepare():

page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;

clears most of page->flags, including PG_skip_kasan_poison, before calling
should_skip_kasan_poison(), which meant that it would never return true
as a result of the page flag being set. Therefore, fix the code to call
should_skip_kasan_poison() before clearing the flags, as we were doing
before the reverted patch.
What are the user visible effects of this change?
Cc: <redacted> # 6.1
Especially if it's cc:stable.

Thanks.

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