Re: [PATCH 04/31] kasan, page_alloc: simplify kasan_poison_pages call site
From: Marco Elver <elver@google.com>
Date: 2021-12-01 14:10:16
Also in:
linux-arm-kernel, lkml
On Tue, Nov 30, 2021 at 10:39PM +0100, andrey.konovalov@linux.dev wrote:
From: Andrey Konovalov <redacted> Simplify the code around calling kasan_poison_pages() in free_pages_prepare(). Reording kasan_poison_pages() and kernel_init_free_pages() is OK, since kernel_init_free_pages() can handle poisoned memory.
Why did they have to be reordered?
quoted hunk ↗ jump to hunk
This patch does no functional changes besides reordering the calls. Signed-off-by: Andrey Konovalov <redacted> --- mm/page_alloc.c | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-)diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3f3ea41f8c64..0673db27dd12 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -1289,6 +1289,7 @@ static __always_inline bool free_pages_prepare(struct page *page, { int bad = 0; bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags);
skip_kasan_poison is only used once now, so you could remove the variable -- unless later code will use it in more than once place again.
quoted hunk ↗ jump to hunk
+ bool init = want_init_on_free(); VM_BUG_ON_PAGE(PageTail(page), page);@@ -1359,19 +1360,10 @@ static __always_inline bool free_pages_prepare(struct page *page, * With hardware tag-based KASAN, memory tags must be set before the * page becomes unavailable via debug_pagealloc or arch_free_page. */ - if (kasan_has_integrated_init()) { - bool init = want_init_on_free(); - - if (!skip_kasan_poison) - kasan_poison_pages(page, order, init); - } else { - bool init = want_init_on_free(); - - if (init) - kernel_init_free_pages(page, 1 << order); - if (!skip_kasan_poison) - kasan_poison_pages(page, order, init); - } + if (!skip_kasan_poison) + kasan_poison_pages(page, order, init); + if (init && !kasan_has_integrated_init()) + kernel_init_free_pages(page, 1 << order); /* * arch_free_page() can make the page's contents inaccessible. s390-- 2.25.1