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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id p31sm706132qtf.11.2020.05.05.22.53.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 May 2020 22:53:33 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH 0/3] kasan: memorize and print call_rcu stack Date: Wed, 6 May 2020 01:53:31 -0400 Message-Id: <2BF68E83-4611-48B2-A57F-196236399219@lca.pw> References: <20200506051853.14380-1-walter-zh.wu@mediatek.com> Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Matthias Brugger , "Paul E . McKenney" , Josh Triplett , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , Andrew Morton , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, wsd_upstream , linux-mediatek@lists.infradead.org In-Reply-To: <20200506051853.14380-1-walter-zh.wu@mediatek.com> To: Walter Wu X-Mailer: iPhone Mail (17D50) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On May 6, 2020, at 1:19 AM, Walter Wu wrote: >=20 > This patchset improves KASAN reports by making them to have > call_rcu() call stack information. It is helpful for programmers > to solve use-after-free or double-free memory issue. >=20 > The KASAN report was as follows(cleaned up slightly): >=20 > BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60 >=20 > Freed by task 0: > save_stack+0x24/0x50 > __kasan_slab_free+0x110/0x178 > kasan_slab_free+0x10/0x18 > kfree+0x98/0x270 > kasan_rcu_reclaim+0x1c/0x60 > rcu_core+0x8b4/0x10f8 > rcu_core_si+0xc/0x18 > efi_header_end+0x238/0xa6c >=20 > First call_rcu() call stack: > save_stack+0x24/0x50 > kasan_record_callrcu+0xc8/0xd8 > call_rcu+0x190/0x580 > kasan_rcu_uaf+0x1d8/0x278 >=20 > Last call_rcu() call stack: > (stack is not available) >=20 >=20 > Add new CONFIG option to record first and last call_rcu() call stack > and KASAN report prints two call_rcu() call stack. >=20 > This option doesn't increase the cost of memory consumption. It is > only suitable for generic KASAN. I don=E2=80=99t understand why this needs to be a Kconfig option at all. If c= all_rcu() stacks are useful in general, then just always gather those inform= ation. How do developers judge if they need to select this option or not?=