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[209.132.180.67]) by mx.google.com with ESMTP id j38si8498893ede.374.2019.10.07.05.22.35; Mon, 07 Oct 2019 05:22:59 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=LHYPKcnf; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727746AbfJGMUK (ORCPT + 99 others); Mon, 7 Oct 2019 08:20:10 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:43696 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727490AbfJGMUK (ORCPT ); Mon, 7 Oct 2019 08:20:10 -0400 Received: by mail-qt1-f196.google.com with SMTP id c4so6078143qtn.10 for ; Mon, 07 Oct 2019 05:20:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=foEkWUCM575fnsqo6dD50iM97OZJEympj2lwIIE9A5g=; b=LHYPKcnfysh/Caiq374/gthsrLoIyk3tHXauOq+eeVZLHdbJJfrDcvWMnP2YRDOG4y o5uB6vwOOlA557aaOrvSnrvdUsLdP6tDbE57H4KMJFVNh3LP+hyNKyQWB8mgP6sbfMwk 7mj/gcuVz6UtV+hEqDDnDPAm8v9hZdZpVm3cCRfysjB5nenQdwqdBbxgL46F9xMZv/tY 8lycVZo65X1EijvrwASG3VLPlK2s6MohOoUoZ9qq8JkoaFH4dF54hK4Bz5PT5q73wR72 cEvq0/v0xrIYrPBFoQZotC6HP9bsE82nGsWHRSnVk6yzliex7OHgj34KO9NeiwPN+CYu 4GSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=foEkWUCM575fnsqo6dD50iM97OZJEympj2lwIIE9A5g=; b=mki4muQbVXo9PbGa7BLhLJRaM1rtPqkkoUTrbSkmyKjI/XZT4JBqBnex32SuVFUamJ UbEPvt33dJtIjxv7KbJK9eCM1Kjbmg7auyKMhnxuuaDDyCiZudkypc8i63/72Ra4yMrf DKFpke9xLfrBW6HKgd79RvE5UIfs05IgAVHLJlRFggMiB7JeDDY6LtHA4l4IwXKSrl+f qQELTioiqs9/9IHvgSUht4TgsKIMA3BqlBwP5rEHwP55z+BMK1dMXeAAWqEy0o/16469 j2Ht/Iwd3Tpu9RUaJhj+c0SrHRMR328yznab2a1NhkL2bySF6mH/T5k1eUPgkxPyg18x /DQA== X-Gm-Message-State: APjAAAXs9CPmf84VZVLaDqFBR7UpdDnW0TCx64seWqiB/OCATJxrSiM8 rXoMbJUGD2kQFt2N1/IoAemBkVrta7Lp9e5dtHqTDoD9KH4= X-Received: by 2002:ac8:108b:: with SMTP id a11mr29317165qtj.380.1570450806687; Mon, 07 Oct 2019 05:20:06 -0700 (PDT) MIME-Version: 1.0 References: <20190927034338.15813-1-walter-zh.wu@mediatek.com> <1569594142.9045.24.camel@mtksdccf07> <1569818173.17361.19.camel@mtksdccf07> <1570018513.19702.36.camel@mtksdccf07> <1570069078.19702.57.camel@mtksdccf07> <1570095525.19702.59.camel@mtksdccf07> <1570110681.19702.64.camel@mtksdccf07> <1570164140.19702.97.camel@mtksdccf07> <1570176131.19702.105.camel@mtksdccf07> <1570182257.19702.109.camel@mtksdccf07> <1570190718.19702.125.camel@mtksdccf07> <1570418576.4686.30.camel@mtksdccf07> <1570436289.4686.40.camel@mtksdccf07> <1570438317.4686.44.camel@mtksdccf07> <1570439032.4686.50.camel@mtksdccf07> <1570440492.4686.59.camel@mtksdccf07> <1570441833.4686.66.camel@mtksdccf07> <1570449804.4686.79.camel@mtksdccf07> In-Reply-To: <1570449804.4686.79.camel@mtksdccf07> From: Dmitry Vyukov Date: Mon, 7 Oct 2019 14:19:54 +0200 Message-ID: Subject: Re: [PATCH] kasan: fix the missing underflow in memmove and memcpy with CONFIG_KASAN_GENERIC=y To: Walter Wu Cc: Andrey Ryabinin , Alexander Potapenko , Matthias Brugger , LKML , kasan-dev , Linux-MM , Linux ARM , linux-mediatek@lists.infradead.org, wsd_upstream Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 7, 2019 at 2:03 PM Walter Wu wrote: > > > > > > > > > On Mon, Oct 7, 2019 at 10:18 AM Walter Wu wrote: > > > > > > > > > > The patchsets help to produce KASAN report when size is negative numbers > > > > > > > > > > in memory operation function. It is helpful for programmer to solve the > > > > > > > > > > undefined behavior issue. Patch 1 based on Dmitry's review and > > > > > > > > > > suggestion, patch 2 is a test in order to verify the patch 1. > > > > > > > > > > > > > > > > > > > > [1]https://bugzilla.kernel.org/show_bug.cgi?id=199341 > > > > > > > > > > [2]https://lore.kernel.org/linux-arm-kernel/20190927034338.15813-1-walter-zh.wu@mediatek.com/ > > > > > > > > > > > > > > > > > > > > Walter Wu (2): > > > > > > > > > > kasan: detect invalid size in memory operation function > > > > > > > > > > kasan: add test for invalid size in memmove > > > > > > > > > > > > > > > > > > > > lib/test_kasan.c | 18 ++++++++++++++++++ > > > > > > > > > > mm/kasan/common.c | 13 ++++++++----- > > > > > > > > > > mm/kasan/generic.c | 5 +++++ > > > > > > > > > > mm/kasan/generic_report.c | 12 ++++++++++++ > > > > > > > > > > mm/kasan/tags.c | 5 +++++ > > > > > > > > > > mm/kasan/tags_report.c | 12 ++++++++++++ > > > > > > > > > > 6 files changed, 60 insertions(+), 5 deletions(-) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > commit 5b3b68660b3d420fd2bd792f2d9fd3ccb8877ef7 > > > > > > > > > > Author: Walter-zh Wu > > > > > > > > > > Date: Fri Oct 4 18:38:31 2019 +0800 > > > > > > > > > > > > > > > > > > > > kasan: detect invalid size in memory operation function > > > > > > > > > > > > > > > > > > > > It is an undefined behavior to pass a negative numbers to > > > > > > > > > > memset()/memcpy()/memmove() > > > > > > > > > > , so need to be detected by KASAN. > > > > > > > > > > > > > > > > > > > > If size is negative numbers, then it has two reasons to be defined > > > > > > > > > > as out-of-bounds bug type. > > > > > > > > > > 1) Casting negative numbers to size_t would indeed turn up as a > > > > > > > > > > large > > > > > > > > > > size_t and its value will be larger than ULONG_MAX/2, so that this > > > > > > > > > > can > > > > > > > > > > qualify as out-of-bounds. > > > > > > > > > > 2) Don't generate new bug type in order to prevent duplicate reports > > > > > > > > > > by > > > > > > > > > > some systems, e.g. syzbot. > > > > > > > > > > > > > > > > > > > > KASAN report: > > > > > > > > > > > > > > > > > > > > BUG: KASAN: out-of-bounds in kmalloc_memmove_invalid_size+0x70/0xa0 > > > > > > > > > > Read of size 18446744073709551608 at addr ffffff8069660904 by task > > > > > > > > > > cat/72 > > > > > > > > > > > > > > > > > > > > CPU: 2 PID: 72 Comm: cat Not tainted > > > > > > > > > > 5.4.0-rc1-next-20191004ajb-00001-gdb8af2f372b2-dirty #1 > > > > > > > > > > Hardware name: linux,dummy-virt (DT) > > > > > > > > > > Call trace: > > > > > > > > > > dump_backtrace+0x0/0x288 > > > > > > > > > > show_stack+0x14/0x20 > > > > > > > > > > dump_stack+0x10c/0x164 > > > > > > > > > > print_address_description.isra.9+0x68/0x378 > > > > > > > > > > __kasan_report+0x164/0x1a0 > > > > > > > > > > kasan_report+0xc/0x18 > > > > > > > > > > check_memory_region+0x174/0x1d0 > > > > > > > > > > memmove+0x34/0x88 > > > > > > > > > > kmalloc_memmove_invalid_size+0x70/0xa0 > > > > > > > > > > > > > > > > > > > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=199341 > > > > > > > > > > > > > > > > > > > > Signed-off-by: Walter Wu > > > > > > > > > > Reported -by: Dmitry Vyukov > > > > > > > > > > Suggested-by: Dmitry Vyukov > > > > > > > > > > > > > > > > > > > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > > > > > > > > > > index 6814d6d6a023..6ef0abd27f06 100644 > > > > > > > > > > --- a/mm/kasan/common.c > > > > > > > > > > +++ b/mm/kasan/common.c > > > > > > > > > > @@ -102,7 +102,8 @@ EXPORT_SYMBOL(__kasan_check_write); > > > > > > > > > > #undef memset > > > > > > > > > > void *memset(void *addr, int c, size_t len) > > > > > > > > > > { > > > > > > > > > > - check_memory_region((unsigned long)addr, len, true, _RET_IP_); > > > > > > > > > > + if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_)) > > > > > > > > > > + return NULL; > > > > > > > > > > > > > > > > > > > > return __memset(addr, c, len); > > > > > > > > > > } > > > > > > > > > > @@ -110,8 +111,9 @@ void *memset(void *addr, int c, size_t len) > > > > > > > > > > #undef memmove > > > > > > > > > > void *memmove(void *dest, const void *src, size_t len) > > > > > > > > > > { > > > > > > > > > > - check_memory_region((unsigned long)src, len, false, _RET_IP_); > > > > > > > > > > - check_memory_region((unsigned long)dest, len, true, _RET_IP_); > > > > > > > > > > + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || > > > > > > > > > > + !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) > > > > > > > > > > + return NULL; > > > > > > > > > > > > > > > > > > > > return __memmove(dest, src, len); > > > > > > > > > > } > > > > > > > > > > @@ -119,8 +121,9 @@ void *memmove(void *dest, const void *src, size_t > > > > > > > > > > len) > > > > > > > > > > #undef memcpy > > > > > > > > > > void *memcpy(void *dest, const void *src, size_t len) > > > > > > > > > > { > > > > > > > > > > - check_memory_region((unsigned long)src, len, false, _RET_IP_); > > > > > > > > > > - check_memory_region((unsigned long)dest, len, true, _RET_IP_); > > > > > > > > > > + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || > > > > > > > > > > + !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) > > > > > > > > > > + return NULL; > > > > > > > > > > > > > > > > > > > > return __memcpy(dest, src, len); > > > > > > > > > > } > > > > > > > > > > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > > > > > > > > > > index 616f9dd82d12..02148a317d27 100644 > > > > > > > > > > --- a/mm/kasan/generic.c > > > > > > > > > > +++ b/mm/kasan/generic.c > > > > > > > > > > @@ -173,6 +173,11 @@ static __always_inline bool > > > > > > > > > > check_memory_region_inline(unsigned long addr, > > > > > > > > > > if (unlikely(size == 0)) > > > > > > > > > > return true; > > > > > > > > > > > > > > > > > > > > + if (unlikely((long)size < 0)) { > > > > > > > > > > + kasan_report(addr, size, write, ret_ip); > > > > > > > > > > + return false; > > > > > > > > > > + } > > > > > > > > > > + > > > > > > > > > > if (unlikely((void *)addr < > > > > > > > > > > kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { > > > > > > > > > > kasan_report(addr, size, write, ret_ip); > > > > > > > > > > diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c > > > > > > > > > > index 36c645939bc9..ed0eb94cb811 100644 > > > > > > > > > > --- a/mm/kasan/generic_report.c > > > > > > > > > > +++ b/mm/kasan/generic_report.c > > > > > > > > > > @@ -107,6 +107,18 @@ static const char *get_wild_bug_type(struct > > > > > > > > > > kasan_access_info *info) > > > > > > > > > > > > > > > > > > > > const char *get_bug_type(struct kasan_access_info *info) > > > > > > > > > > { > > > > > > > > > > + /* > > > > > > > > > > + * If access_size is negative numbers, then it has two reasons > > > > > > > > > > + * to be defined as out-of-bounds bug type. > > > > > > > > > > + * 1) Casting negative numbers to size_t would indeed turn up as > > > > > > > > > > + * a 'large' size_t and its value will be larger than ULONG_MAX/2, > > > > > > > > > > + * so that this can qualify as out-of-bounds. > > > > > > > > > > + * 2) Don't generate new bug type in order to prevent duplicate > > > > > > > > > > reports > > > > > > > > > > + * by some systems, e.g. syzbot. > > > > > > > > > > + */ > > > > > > > > > > + if ((long)info->access_size < 0) > > > > > > > > > > + return "out-of-bounds"; > > > > > > > > > > > > > > > > > > "out-of-bounds" is the _least_ frequent KASAN bug type. It won't > > > > > > > > > prevent duplicates. "heap-out-of-bounds" is the frequent one. > > > > > > > > > > > > > > > > > > > > > > > > /* > > > > > > > > * If access_size is negative numbers, then it has two reasons > > > > > > > > * to be defined as out-of-bounds bug type. > > > > > > > > * 1) Casting negative numbers to size_t would indeed turn up as > > > > > > > > * a "large" size_t and its value will be larger than ULONG_MAX/2, > > > > > > > > * so that this can qualify as out-of-bounds. > > > > > > > > * 2) Don't generate new bug type in order to prevent duplicate > > > > > > > > reports > > > > > > > > * by some systems, e.g. syzbot. "out-of-bounds" is the _least_ > > > > > > > > frequent KASAN bug type. > > > > > > > > * It won't prevent duplicates. "heap-out-of-bounds" is the > > > > > > > > frequent one. > > > > > > > > */ > > > > > > > > > > > > > > > > We directly add it into the comment. > > > > > > > > > > > > > > > > > > > > > OK, let's start from the beginning: why do you return "out-of-bounds" here? > > > > > > > > > > > > > Uh, comment 1 and 2 should explain it. :) > > > > > > > > > > The comment says it will cause duplicate reports. It does not explain > > > > > why you want syzbot to produce duplicate reports and spam kernel > > > > > developers... So why do you want that? > > > > > > > > > We don't generate new bug type in order to prevent duplicate by some > > > > systems, e.g. syzbot. Is it right? If yes, then it should not have > > > > duplicate report. > > > > > > > Sorry, because we don't generate new bug type. it should be duplicate > > > report(only one report which may be oob or size invlid), > > > the duplicate report goal is that invalid size is oob issue, too. > > > > > > I would not introduce a new bug type. > > > These are parsed and used by some systems, e.g. syzbot. If size is > > > user-controllable, then a new bug type for this will mean 2 bug > > > reports. > > > > To prevent duplicates, the new crash title must not just match _any_ > > crash title that kernel can potentially produce. It must match exactly > > the crash that kernel produces for this bug on other input data. > > > > Consider, userspace passes size=123, KASAN produces "heap-out-of-bounds in foo". > > Now userspace passes size=-1 and KASAN produces "invalid-size in foo". > > This will be a duplicate bug report. > > Now if KASAN will produce "out-of-bounds in foo", it will also lead to > > a duplicate report. > > Only iff KASAN will produce "heap-out-of-bounds in foo" for size=-1, > > it will not lead to a duplicate report. > > I think it is not easy to avoid the duplicate report(mentioned above). > As far as my knowledge is concerned, KASAN is memory corruption detector > in kernel space, it should only detect memory corruption and don't > distinguish whether it is passed by userspace. if we want to do, then we > may need to parse backtrace to check if it has copy_form_user() or other > function? My idea was just to always print "heap-out-of-bounds" and don't differentiate if the size come from userspace or not.