From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2AD63EAC78 for ; Tue, 17 Mar 2026 15:12:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773760358; cv=none; b=ZwWIZCD8ixrC3UBwV/ei1yP0/xXQlrnkWt9PMG/fD81UlZ080SyFnLR/lJL6kN5q7XYAMbUXhBEB8je0soOLZyNHG1gEpyjbxMCPAVhzI+HkseJioIcefaH6BZP5sY3rb7YghS2DZaCdZnqNWl6Kpp0rkrbK058mhW7lNliru90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773760358; c=relaxed/simple; bh=oXss1Qhz5NOqCruVAuKSAobY8d1H+KGulKPdY3vvH4k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hM845yaUd/rWsqrHgGBmeIxkDH9IWFjVORsT9DjIG6PaA3q5aLTQ+blnvOWcRdfumrF2qFRpo8fV7hG/Wpn4bHarjwUqO44EjPtotcUds9TBCxYGDKUW8dWZFys4bGRL9Owl/Qc7Z7v6cVPwAvdPTka9Tp4ldvJ5cr43mCCDJ+M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZFzYzubu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZFzYzubu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4FC3EC2BC86; Tue, 17 Mar 2026 15:12:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773760357; bh=oXss1Qhz5NOqCruVAuKSAobY8d1H+KGulKPdY3vvH4k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZFzYzubutCmeOQDGMuJwCuWQ/FomCS25AxeMrAQqWpwAavXRd/EvjbE8d96s/YKMG VqO/SpkbZ4ReUtE0NxDQIkaIRG6fyysQUlPE1mrQDn2+Unhy/d5mbjuuHp+z6vPjBW vF+Dj7fLxeX6tZFkPK75mud47AZjAAOZJJuWTreQX9YHrrMVwUf9VlqNFnJNroW+wo g6/NAYozxF2yTuxiACnWFF4vLBz8h6E3UU2fMcTP4A4AvMg5nQibGH3O9dTzs9SWbm f00VTGD8G1Eovr6YC/ak8zdWbv4DIA4l89DhWXbsrVTVd7u9RSdsVkJ9JO2I2R1Z/j IVqizxGWf8u7w== From: Sasha Levin To: stable@vger.kernel.org Cc: Alexander Potapenko , Ernesto Martinez Garcia , Andrey Konovalov , Andrey Ryabinin , Dmitry Vyukov , Greg KH , Kees Cook , Marco Elver , Andrew Morton , Sasha Levin Subject: [PATCH 6.1.y] mm/kfence: fix KASAN hardware tag faults during late enablement Date: Tue, 17 Mar 2026 11:12:34 -0400 Message-ID: <20260317151234.185462-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2026031730-shucking-dreaded-e3cf@gregkh> References: <2026031730-shucking-dreaded-e3cf@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Alexander Potapenko [ Upstream commit d155aab90fffa00f93cea1f107aef0a3d548b2ff ] When KASAN hardware tags are enabled, re-enabling KFENCE late (via /sys/module/kfence/parameters/sample_interval) causes KASAN faults. This happens because the KFENCE pool and metadata are allocated via the page allocator, which tags the memory, while KFENCE continues to access it using untagged pointers during initialization. Use __GFP_SKIP_KASAN for late KFENCE pool and metadata allocations to ensure the memory remains untagged, consistent with early allocations from memblock. To support this, add __GFP_SKIP_KASAN to the allowlist in __alloc_contig_verify_gfp_mask(). Link: https://lkml.kernel.org/r/20260220144940.2779209-1-glider@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Alexander Potapenko Suggested-by: Ernesto Martinez Garcia Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Greg KH Cc: Kees Cook Cc: Marco Elver Cc: Signed-off-by: Andrew Morton [ expand __GFP_SKIP_KASAN + nr_pages_pool => nr_pages ] Signed-off-by: Sasha Levin --- mm/kfence/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index edf6deb382b67..bdb864384f2af 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -897,7 +897,8 @@ static int kfence_init_late(void) #ifdef CONFIG_CONTIG_ALLOC struct page *pages; - pages = alloc_contig_pages(nr_pages, GFP_KERNEL, first_online_node, NULL); + pages = alloc_contig_pages(nr_pages, GFP_KERNEL | __GFP_SKIP_KASAN_UNPOISON | + __GFP_SKIP_KASAN_POISON, first_online_node, NULL); if (!pages) return -ENOMEM; __kfence_pool = page_to_virt(pages); @@ -906,7 +907,9 @@ static int kfence_init_late(void) pr_warn("KFENCE_NUM_OBJECTS too large for buddy allocator\n"); return -EINVAL; } - __kfence_pool = alloc_pages_exact(KFENCE_POOL_SIZE, GFP_KERNEL); + __kfence_pool = alloc_pages_exact(KFENCE_POOL_SIZE, GFP_KERNEL | + __GFP_SKIP_KASAN_UNPOISON | + __GFP_SKIP_KASAN_POISON); if (!__kfence_pool) return -ENOMEM; #endif -- 2.51.0