[PATCH AUTOSEL 5.18 10/53] mm: kasan: Skip page unpoisoning only if __GFP_SKIP_KASAN_UNPOISON

[Sasha Levin]

From: Catalin Marinas <catalin.marinas@xxxxxxx>

[ Upstream commit 6d05141a393071e104bf5be5ad4d0c79c6dff343 ]

Currently post_alloc_hook() skips the kasan unpoisoning if the tags will
be zeroed (__GFP_ZEROTAGS) or __GFP_SKIP_KASAN_UNPOISON is passed. Since
__GFP_ZEROTAGS is now accompanied by __GFP_SKIP_KASAN_UNPOISON, remove
the extra check.

Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Link: https://lore.kernel.org/r/20220610152141.2148929-4-catalin.marinas@xxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/page_alloc.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index edef84efba76..2a894ba742e4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2346,7 +2346,7 @@ static inline bool check_new_pcp(struct page *page, unsigned int order)
 }
 #endif /* CONFIG_DEBUG_VM */
 
-static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
+static inline bool should_skip_kasan_unpoison(gfp_t flags)
 {
 	/* Don't skip if a software KASAN mode is enabled. */
 	if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
@@ -2358,12 +2358,10 @@ static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
 		return true;
 
 	/*
-	 * With hardware tag-based KASAN enabled, skip if either:
-	 *
-	 * 1. Memory tags have already been cleared via tag_clear_highpage().
-	 * 2. Skipping has been requested via __GFP_SKIP_KASAN_UNPOISON.
+	 * With hardware tag-based KASAN enabled, skip if this has been
+	 * requested via __GFP_SKIP_KASAN_UNPOISON.
 	 */
-	return init_tags || (flags & __GFP_SKIP_KASAN_UNPOISON);
+	return flags & __GFP_SKIP_KASAN_UNPOISON;
 }
 
 static inline bool should_skip_init(gfp_t flags)
@@ -2415,7 +2413,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 		/* Note that memory is already initialized by the loop above. */
 		init = false;
 	}
-	if (!should_skip_kasan_unpoison(gfp_flags, init_tags)) {
+	if (!should_skip_kasan_unpoison(gfp_flags)) {
 		/* Unpoison shadow memory or set memory tags. */
 		kasan_unpoison_pages(page, order, init);
 
-- 
2.35.1