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Thu, 06 Mar 2025 17:10:23 -0800 (PST) MIME-Version: 1.0 References: <168f775c4587f3a1338271390204a9fe16b150dd.1739866028.git.maciej.wieczor-retman@intel.com> In-Reply-To: From: Andrey Konovalov Date: Fri, 7 Mar 2025 02:10:12 +0100 X-Gm-Features: AQ5f1JqsmdGRGu2uHlQaWnjOnFHn8usJJdOQ1XiECzwCgn8ytUJNZ-8vyFlkmEo Message-ID: Subject: Re: [PATCH v2 01/14] kasan: sw_tags: Use arithmetic shift for shadow computation To: Maciej Wieczor-Retman Cc: kees@kernel.org, julian.stecklina@cyberus-technology.de, kevinloughlin@google.com, peterz@infradead.org, tglx@linutronix.de, justinstitt@google.com, catalin.marinas@arm.com, wangkefeng.wang@huawei.com, bhe@redhat.com, ryabinin.a.a@gmail.com, kirill.shutemov@linux.intel.com, will@kernel.org, ardb@kernel.org, jason.andryuk@amd.com, dave.hansen@linux.intel.com, pasha.tatashin@soleen.com, guoweikang.kernel@gmail.com, dwmw@amazon.co.uk, mark.rutland@arm.com, broonie@kernel.org, apopple@nvidia.com, bp@alien8.de, rppt@kernel.org, kaleshsingh@google.com, richard.weiyang@gmail.com, luto@kernel.org, glider@google.com, pankaj.gupta@amd.com, pawan.kumar.gupta@linux.intel.com, kuan-ying.lee@canonical.com, tony.luck@intel.com, tj@kernel.org, jgross@suse.com, dvyukov@google.com, baohua@kernel.org, samuel.holland@sifive.com, dennis@kernel.org, akpm@linux-foundation.org, thomas.weissschuh@linutronix.de, surenb@google.com, kbingham@kernel.org, ankita@nvidia.com, nathan@kernel.org, ziy@nvidia.com, xin@zytor.com, rafael.j.wysocki@intel.com, andriy.shevchenko@linux.intel.com, cl@linux.com, jhubbard@nvidia.com, hpa@zytor.com, scott@os.amperecomputing.com, david@redhat.com, jan.kiszka@siemens.com, vincenzo.frascino@arm.com, corbet@lwn.net, maz@kernel.org, mingo@redhat.com, arnd@arndb.de, ytcoode@gmail.com, xur@google.com, morbo@google.com, thiago.bauermann@linaro.org, linux-doc@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: c1s5xcqiuqxekudbw7jfdchi3tncfanf X-Rspamd-Queue-Id: 31B6F100009 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1741309824-764977 X-HE-Meta: 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 78vYWen0 J9dbqpCHsSlXIoXS6D5buuwCP+RKZG3AfKXWoytUqGDtzq0edjbu9Du5SC9SG6kujZ/N70HZao9sEeifJXi85T2NY8KP0IkZ62GH4NpK6zjV3iAWLuAhGc4TA9vBgVe3fOml3jxn82gpdlqQDLnLjLyEIsuz3xCAoZPi4TElErFb5NCtvfIgnIKR63MPn0G+tS2w2qF68ELpsxHWmYIWH3zQ9+TXvPKxY5ufhF69zdMR/F/sHDB37qekBbRQYCEZ83TPe4qeZlQ5XaVyaPWTliThWgysvnG0WaPDBC+PV7tkOWJ5HMep7KSZXk5bQngejzrOr3lucddsOimtZuJdhXc5ENU+eeDp9gEcC/cvdA8gtf2Itn0Z8tFqPW0eMzalirB6Aqe8WpkoFTb4jHjWLn0p+37MMHWsnQHvQvhSJFDfdaaOMV8sGajbgTG6ZRZl6FcnsqFirvg03TaA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000135, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 4, 2025 at 1:31=E2=80=AFPM Maciej Wieczor-Retman wrote: > > One other question that came to me about how KASAN works, is there some > mechanism to prevent data races between two threads? In the compiler perh= aps? > > For example memory is de-allocated and shadow memory is poisoned but some= other > thread was just about to do a shadow memory check and was interrupted? > > I've read the kasan/vmalloc.c comments and from them I'd extrapolate that= the > caller needs to make sure there are not data races / memory barriers are = in > place. KASAN does nothing to deliberately prevent or detect races. Even if the race leads to an OOB or UAF, KASAN might not be able to detect it. But sometimes it does: if poisoned shadow memory values become visible to the other thread/CPU before it makes a shadow memory value check.