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 E42D725E44D; Thu, 28 Aug 2025 09:50:46 +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=1756374647; cv=none; b=TcZ5ZLuVdLO4eRM1DDr3ONnJOB71mdw0F6PM4F/FV038kuKx+KbaLnMGY7xsbXkjXrt0YJN8PwnthL1Utt2YPVRipH89hqNpAVETxcFQ3AGs0+WSDMlQ+UoNUpXMy1L9yXC2T2SJ2rt3uXVqCOzfXkAD6QQ+0zEN3ARih7AWUcY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756374647; c=relaxed/simple; bh=nsd/srhjb2GA1BGIBjZu6MLWkDZmOCy2pcy5zHmDL74=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZVKgl0PvZuXD4tAhn7tkkYDKi00pQkeXJx9S2jVFzf2T/7CqFuvQJB9DsJAdHJxCrkr7xMKup4nsJjHi5zZPuksJggTeWuSA84+PdfqNfM4bs8LfVvSxuw72HFflfmucOaceB52SrLwp9fCzDg7K7SKP5nze5YteENkie5skcXg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VtsLfDMM; 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="VtsLfDMM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2032C4CEEB; Thu, 28 Aug 2025 09:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756374646; bh=nsd/srhjb2GA1BGIBjZu6MLWkDZmOCy2pcy5zHmDL74=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VtsLfDMMLPSn8X7FB1qyNCklBXX9jl5VJY1SBRcbhOVICoFXA67QPx/qy7W6dd3vD yfVYCeZ9qxnPjnysPEtIFtXsq9TpqQ7ht02VkXWKJSH5mhi7sLsK8f6czjwjLvDknI EM7JLLbBT14GmJfNk3pIinT5sdlwUfUTxOOuJcXPVeVRMUQIKLsvsdrWX0j4LVT7gq SCz62qpwpxFqTRTlUURPRhZQBzchubGPagz85CseSPu0lif/72BG8k0aV+YX0q1VLD e4NAgp3YEZ2oeqsVUxXVdVb/8ObVWHiurodKtnBRh0zfOBY24G5vDUPm3Vou9eV7r2 4uhT7unkY+MBg== Date: Thu, 28 Aug 2025 12:50:19 +0300 From: Mike Rapoport To: Maciej Wieczor-Retman Cc: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de, x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5 07/19] mm: x86: Untag addresses in EXECMEM_ROX related pointer arithmetic Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 25, 2025 at 10:24:32PM +0200, Maciej Wieczor-Retman wrote: > ARCH_HAS_EXECMEM_ROX was re-enabled in x86 at Linux 6.14 release. > Related code has multiple spots where page virtual addresses end up used > as arguments in arithmetic operations. Combined with enabled tag-based > KASAN it can result in pointers that don't point where they should or > logical operations not giving expected results. > > vm_reset_perms() calculates range's start and end addresses using min() > and max() functions. To do that it compares pointers but some are not > tagged - addr variable is, start and end variables aren't. > > within() and within_range() can receive tagged addresses which get > compared to untagged start and end variables. > > Reset tags in addresses used as function arguments in min(), max(), > within(). > > execmem_cache_add() adds tagged pointers to a maple tree structure, > which then are incorrectly compared when walking the tree. That results > in different pointers being returned later and page permission violation > errors panicking the kernel. > > Reset tag of the address range inserted into the maple tree inside > execmem_cache_add(). > > Signed-off-by: Maciej Wieczor-Retman > --- > Changelog v5: > - Remove the within_range() change. > - arch_kasan_reset_tag -> kasan_reset_tag. > > Changelog v4: > - Add patch to the series. > > mm/execmem.c | 2 +- > mm/vmalloc.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/execmem.c b/mm/execmem.c > index 0822305413ec..f7b7bdacaec5 100644 > --- a/mm/execmem.c > +++ b/mm/execmem.c > @@ -186,7 +186,7 @@ static DECLARE_WORK(execmem_cache_clean_work, execmem_cache_clean); > static int execmem_cache_add_locked(void *ptr, size_t size, gfp_t gfp_mask) > { > struct maple_tree *free_areas = &execmem_cache.free_areas; > - unsigned long addr = (unsigned long)ptr; > + unsigned long addr = (unsigned long)kasan_reset_tag(ptr); Thinking more about it, we anyway reset tag in execmem_alloc() and return untagged pointer to the caller. Let's just move kasan_reset_tag() to execmem_vmalloc() so that we always use untagged pointers. Seems more robust to me. > MA_STATE(mas, free_areas, addr - 1, addr + 1); > unsigned long lower, upper; > void *area = NULL; > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 6dbcdceecae1..c93893fb8dd4 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3322,7 +3322,7 @@ static void vm_reset_perms(struct vm_struct *area) > * the vm_unmap_aliases() flush includes the direct map. > */ > for (i = 0; i < area->nr_pages; i += 1U << page_order) { > - unsigned long addr = (unsigned long)page_address(area->pages[i]); > + unsigned long addr = (unsigned long)kasan_reset_tag(page_address(area->pages[i])); This is not strictly related to execemem, there may other users of VM_FLUSH_RESET_PERMS. Regardless, I wonder how this works on arm64 with tags enabled? Also, it's not the only place in the kernel that does (unsigned long)page_address(page). Do other sites need to reset the tag as well? > > if (addr) { > unsigned long page_size; > -- > 2.50.1 > -- Sincerely yours, Mike.