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kasan: reset page tags properly with sampling
The implementation of page_alloc poisoning sampling assumed that tag_clear_highpage resets page tags for __GFP_ZEROTAGS allocations. However, this is no longer the case since commit 70c248a ("mm: kasan: Skip unpoisoning of user pages"). This leads to kernel crashes when MTE-enabled userspace mappings are used with Hardware Tag-Based KASAN enabled. Reset page tags for __GFP_ZEROTAGS allocations in post_alloc_hook(). Also clarify and fix related comments. [[email protected]: update comment] Link: https://lkml.kernel.org/r/5dbd866714b4839069e2d8469ac45b60953db290.1674592780.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/24ea20c1b19c2b4b56cf9f5b354915f8dbccfc77.1674592496.git.andreyknvl@google.com Fixes: 44383ce ("kasan: allow sampling page_alloc allocations for HW_TAGS") Signed-off-by: Andrey Konovalov <[email protected]> Reported-by: Peter Collingbourne <[email protected]> Tested-by: Peter Collingbourne <[email protected]> Cc: Alexander Potapenko <[email protected]> Cc: Andrey Ryabinin <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: Marco Elver <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
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