From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (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 F305938DE0 for ; Thu, 5 Dec 2024 02:15:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733364953; cv=none; b=Bmn2qhKLZT1npvBQq69RWstqTWzrltaFXyWL0uREF+2Zd0qh6QdBFt8niTO9eYpWzVGeuB/iiqrZJEm7mfLwx9KDhN0R9REUA4ejrvSGioK9ZJ5EIjXxF0viN12pmMJNqrtcv1gZk6rX9yFIaBlJQBbDous2lG9gEft4t8BxiUY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733364953; c=relaxed/simple; bh=FXtpBHZbgVW0KjhcerodMhEz108fjp4cOcRcL9tbflY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nkKM5RFcaLoCYALQKR8OvFyhfS5FuIedO2EYq2/yk3HEWL0lqNxexe8s9w1uBo7MPFAktmHOcE1zflj5ubf9sUI/XrIQatZ5QtR+Fso7MuGwAa7PIpWUIdvyyAycCvXE7g1l0UpLpbj8k5pgCDgtlybYOaPjzRf4e60Gus7siVc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=fBlGrEdS; arc=none smtp.client-ip=91.218.175.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="fBlGrEdS" Message-ID: <6dab626e-acee-9f4e-c97b-7a225882edff@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1733364947; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pRTPO6yPQbL/JsKyn6272w8a89k5009o0qPxqVnHQWI=; b=fBlGrEdS0bOFerVMMX/sNiJHYQf6S6xmGrK0f8XAF7HGv/9JWAzBZX8B/238JkqS+aBBXv zb8HT2Ho4b6XAOvtUxbqR8CZ4OTETsf0kq/sB/J+NKewNEkM6COGVJqTmIOZWgwmRL76+G jPFSaLD3GY+BZuWd8Fwb5wniRdM1HB4= Date: Thu, 5 Dec 2024 10:14:54 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2] mm/alloc_tag: fix vm_module_tags_populate's KASAN poisoning logic To: Suren Baghdasaryan Cc: kent.overstreet@linux.dev, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge References: <20241204075248.384215-1-hao.ge@linux.dev> <20241204083448.387862-1-hao.ge@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Hi Suren On 12/5/24 03:33, Suren Baghdasaryan wrote: > On Wed, Dec 4, 2024 at 7:08 AM Hao Ge wrote: >> Hi Suren >> >> >> Thank you for your review. >> >> >> On 12/4/24 22:39, Suren Baghdasaryan wrote: >>> On Wed, Dec 4, 2024 at 12:35 AM Hao Ge wrote: >>>> From: Hao Ge >>>> >>>> After merge commit 233e89322cbe ("alloc_tag: >>>> fix module allocation tags populated area calculation"), >>>> We still encountered a KASAN bug. >>>> >>>> This is because we have only actually performed >>>> page allocation and address mapping here. >>>> we need to unpoisoned portions of underlying memory. >>>> >>>> Because we have a change in the size here,we need to >>>> re-annotate poisoned and unpoisoned portions of underlying memory >>>> according to the new size. >>>> >>>> Here is the log for KASAN: >>>> >>>> [ 5.041171][ T1] ================================================================== >>>> [ 5.042047][ T1] BUG: KASAN: vmalloc-out-of-bounds in move_module+0x2c0/0x708 >>>> [ 5.042723][ T1] Write of size 240 at addr ffff80007e510000 by task systemd/1 >>>> [ 5.043412][ T1] >>>> [ 5.043523][ T72] input: QEMU QEMU USB Tablet as /devices/pci0000:00/0000:00:01.1/0000:02:001 >>>> [ 5.043614][ T1] CPU: 0 UID: 0 PID: 1 Comm: systemd Not tainted 6.13.0-rc1+ #28 >>>> [ 5.045560][ T1] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 >>>> [ 5.046328][ T1] Call trace: >>>> [ 5.046670][ T1] show_stack+0x20/0x38 (C) >>>> [ 5.047127][ T1] dump_stack_lvl+0x80/0xf8 >>>> [ 5.047533][ T1] print_address_description.constprop.0+0x58/0x358 >>>> [ 5.048092][ T72] hid-generic 0003:0627:0001.0001: input,hidraw0: USB HID v0.01 Mouse [QEMU 0 >>>> [ 5.048126][ T1] print_report+0xb0/0x280 >>>> [ 5.049682][ T1] kasan_report+0xb8/0x108 >>>> [ 5.050170][ T1] kasan_check_range+0xe8/0x190 >>>> [ 5.050685][ T1] memcpy+0x58/0xa0 >>>> [ 5.051135][ T1] move_module+0x2c0/0x708 >>>> [ 5.051586][ T1] layout_and_allocate.constprop.0+0x308/0x5b8 >>>> [ 5.052219][ T1] load_module+0x134/0x16c8 >>>> [ 5.052671][ T1] init_module_from_file+0xdc/0x138 >>>> [ 5.053193][ T1] idempotent_init_module+0x344/0x600 >>>> [ 5.053742][ T1] __arm64_sys_finit_module+0xbc/0x150 >>>> [ 5.054289][ T1] invoke_syscall+0xd4/0x258 >>>> [ 5.054749][ T1] el0_svc_common.constprop.0+0xb4/0x240 >>>> [ 5.055319][ T1] do_el0_svc+0x48/0x68 >>>> [ 5.055743][ T1] el0_svc+0x40/0xe0 >>>> [ 5.056142][ T1] el0t_64_sync_handler+0x10c/0x138 >>>> [ 5.056658][ T1] el0t_64_sync+0x1ac/0x1b0 >>>> >>>> Fixes: 233e89322cbe ("alloc_tag: fix module allocation tags populated area calculation") >>>> Signed-off-by: Hao Ge >>> Thanks for the fix! >>> >>>> --- >>>> v2: Add comments to kasan_unpoison_vmalloc like other places. >>>> >>>> commit 233e89322cbe ("alloc_tag: fix module allocation >>>> tags populated area calculation") is currently in the >>>> mm-hotfixes-unstable branch, so this patch is >>>> developed based on the mm-hotfixes-unstable branch. >>>> --- >>>> lib/alloc_tag.c | 13 +++++++++++++ >>>> 1 file changed, 13 insertions(+) >>>> >>>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c >>>> index 4ee6caa6d2da..f885b3f3af0e 100644 >>>> --- a/lib/alloc_tag.c >>>> +++ b/lib/alloc_tag.c >>>> @@ -421,7 +421,20 @@ static int vm_module_tags_populate(void) >>>> __free_page(next_page[i]); >>>> return -ENOMEM; >>>> } >>>> + >>>> + kasan_poison_vmalloc((void *)module_tags.start_addr, >>>> + vm_module_tags->nr_pages << PAGE_SHIFT); >>>> + >>>> vm_module_tags->nr_pages += nr; >>>> + >>>> + /* >>>> + * Mark the pages as accessible, now that they are mapped. >>>> + * With hardware tag-based KASAN, marking is skipped for >>>> + * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc(). >>>> + */ >>>> + kasan_unpoison_vmalloc((void *)module_tags.start_addr, >>>> + vm_module_tags->nr_pages << PAGE_SHIFT, >>>> + KASAN_VMALLOC_PROT_NORMAL); >>> Instead of poisoning [module_tags.start_addr, >>> vm_module_tags->nr_pages], incrementing vm_module_tags->nr_pages and >>> the unpoisoning [module_tags.start_addr, vm_module_tags->nr_pages] >>> could we simply poisons the additional area like this: >>> >>> kasan_unpoison_vmalloc((void *)module_tags.start_addr + >>> (vm_module_tags->nr_pages << PAGE_SHIFT), >>> nr << PAGE_SHIFT, >>> KASAN_VMALLOC_PROT_NORMAL); >>> vm_module_tags->nr_pages += nr; >>> ? >> >> I had considered making such modifications earlier. >> >> But considering the following situation, >> >> A module tags spans across the regions of [module_tags.start_addr, >> vm_module_tags->nr_pages] and [module_tags.start_addr + >> vm_module_tags->nr_pages, ...]. >> >> It may result in false positives for out-of-bounds errors. > Sorry, maybe I'm missing something but I don't see why poisoning only > newly mapped area would lead to false positives. Could you please > clarify? Because KASAN may perceive the two as distinct address spaces, despite their addresses being contiguous. So, when a module tag spans across these two contiguous address spaces, KASAN may incorrectly consider it as an out-of-bounds access. > Also, if you do need to unpoison and then poison, using phys_end and > new_end would be better, like this: > > kasan_poison_vmalloc((void *)module_tags.start_addr, > phys_end - module_tags.start_addr) > > kasan_unpoison_vmalloc((void *)module_tags.start_addr, > new_end - module_tags.start_addr, > KASAN_VMALLOC_PROT_NORMAL); OK, the next version will include. Thanks Best regards Hao >> >>>> } >>>> >>>> return 0; >>>> -- >>>> 2.25.1 >>>>