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 3A8BC357A4A; Tue, 17 Mar 2026 16:50:18 +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=1773766218; cv=none; b=K5VY06+5LeCjBa0dz3dDull6+TOoU7m81O2bJfRyHljKAmYWX3LLGIE5imTvvH0zc3HgGHxw+Gq8Bhsm/20kQaDsYlS22DFdp3FRAoGwAaYOfNkeWPPbxWLGs4dKtUEQoCqaHWApk82HOG1sOWj8tLKZhEqp5I/FVEDEqs49dhU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773766218; c=relaxed/simple; bh=1skMiiTjKLoH2xM1vWVPHh03JGJhGblWqJrSNNueyPQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hE4CSFcJljy91s56CxfMnQsEwcFhJjTpsEZwWkBmY9lazIQnYKoqbZ1pM4i/1hLyeMPQfMxxGqvDwPOoOVRrwaAfIP0Qd7jBb19uF2b1Lc8XBoXGjfmlLWFSobFw14kcOWQfYb7Jk8Vn+SYZppYmcKvZiE0i6QtoUq/x1ApA1Sk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qGCcxe36; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qGCcxe36" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B39AC4CEF7; Tue, 17 Mar 2026 16:50:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1773766218; bh=1skMiiTjKLoH2xM1vWVPHh03JGJhGblWqJrSNNueyPQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qGCcxe36AfQMkNRkUwsdkxRni5+1GimP+S4yrCiDnuyQlQhVSq8hqQV3iQJaZDo9J hgPCYgeMH2gJe0qTuqlHMucC3PCWE/R1wpkdBDw0w5xz/zHA9ZS5NZ41sfCqt/hPpA i08f33AYbUnKq1lBGVmNlLHuhkr+763M8o67HRbU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexander Potapenko , Ernesto Martinez Garcia , Andrey Konovalov , Andrey Ryabinin , Dmitry Vyukov , Kees Cook , Marco Elver , Andrew Morton Subject: [PATCH 6.19 194/378] mm/kfence: fix KASAN hardware tag faults during late enablement Date: Tue, 17 Mar 2026 17:32:31 +0100 Message-ID: <20260317163014.142746981@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260317163006.959177102@linuxfoundation.org> References: <20260317163006.959177102@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexander Potapenko commit d155aab90fffa00f93cea1f107aef0a3d548b2ff upstream. 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 Signed-off-by: Greg Kroah-Hartman --- mm/kfence/core.c | 14 ++++++++------ mm/page_alloc.c | 3 ++- 2 files changed, 10 insertions(+), 7 deletions(-) --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -984,14 +984,14 @@ static int kfence_init_late(void) #ifdef CONFIG_CONTIG_ALLOC struct page *pages; - pages = alloc_contig_pages(nr_pages_pool, GFP_KERNEL, first_online_node, - NULL); + pages = alloc_contig_pages(nr_pages_pool, GFP_KERNEL | __GFP_SKIP_KASAN, + first_online_node, NULL); if (!pages) return -ENOMEM; __kfence_pool = page_to_virt(pages); - pages = alloc_contig_pages(nr_pages_meta, GFP_KERNEL, first_online_node, - NULL); + pages = alloc_contig_pages(nr_pages_meta, GFP_KERNEL | __GFP_SKIP_KASAN, + first_online_node, NULL); if (pages) kfence_metadata_init = page_to_virt(pages); #else @@ -1001,11 +1001,13 @@ static int kfence_init_late(void) 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); if (!__kfence_pool) return -ENOMEM; - kfence_metadata_init = alloc_pages_exact(KFENCE_METADATA_SIZE, GFP_KERNEL); + kfence_metadata_init = alloc_pages_exact(KFENCE_METADATA_SIZE, + GFP_KERNEL | __GFP_SKIP_KASAN); #endif if (!kfence_metadata_init) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6941,7 +6941,8 @@ static int __alloc_contig_verify_gfp_mas { const gfp_t reclaim_mask = __GFP_IO | __GFP_FS | __GFP_RECLAIM; const gfp_t action_mask = __GFP_COMP | __GFP_RETRY_MAYFAIL | __GFP_NOWARN | - __GFP_ZERO | __GFP_ZEROTAGS | __GFP_SKIP_ZERO; + __GFP_ZERO | __GFP_ZEROTAGS | __GFP_SKIP_ZERO | + __GFP_SKIP_KASAN; const gfp_t cc_action_mask = __GFP_RETRY_MAYFAIL | __GFP_NOWARN; /*