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Tue, 18 Mar 2025 08:32:58 -0700 (PDT) MIME-Version: 1.0 References: <168f775c4587f3a1338271390204a9fe16b150dd.1739866028.git.maciej.wieczor-retman@intel.com> In-Reply-To: From: Andrey Konovalov Date: Tue, 18 Mar 2025 16:32:46 +0100 X-Gm-Features: AQ5f1JrJPlldmh-W4saMlKXW0Ok9D48DqwKxa7GZ64X93-bATE_KAdVxzbhhhSM 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-Rspam-User: X-Rspamd-Queue-Id: 73BA51C001B X-Rspamd-Server: rspam08 X-Stat-Signature: gmwfnqzako4wufnfbz33x4ws79p4szy7 X-HE-Tag: 1742311980-806159 X-HE-Meta: U2FsdGVkX18ttgEBhWhjccv0W6J1zscPtqfptM7HUtswnMxX2RWtanp3bXHoqvSxATaMMD/8X8wt27jWhr/XrCs+hRrNWXgRNfIggPtDINAO2v8288t+36/tCsyi6J2npbcWkw40pytHRE11ICTZLXElluiO5meZVUCU0RqLgGPvRpyMY95uHgfSVZIVdcHT+mtinWfA34TNTjFVYOVvdRcn1EcM++lZVagHsDOYuxTrWabbCkcaOTvsfmUfSj3NdxIBzUinLwHiRJUcqqXju7Fghp7i/tyHxxGpVbRxrhqN/pBUdvJXPad17dgqn2tXQuxKEY9xrJlijtHCOpy82eBsTATFa6DbZtesyjIWxasMJkB4ojUmHnxb6umsMGKndt4sH/ecW0/c6OLIqET/bin5beb4Iwx0CWmOa6IcTzQ1U+i2H5CmRDMD5NPWetNQWE/0pGwmHDHfqoqQyW9OZm8cutcXxhT85bpD0SG11nCUQEcaTTtSElwp98Gma6Y4s1rYLz7PxDjZvFYj7623MJ22rD/wKxn9Yu91O0rLk/KqyLPP4Wl4Pl9jbUvPoZlJjKXEgUZbeVKoUmoQslIpINh+mndbbqKOkgCSUQ8a5YG4Ok0ZmGuf3RqDZ+nciFAxWcMMXYbslGl+3i23RV9VhkckszNtC6BtkBuPVRimQno1MVmYXAz4BXrYw3RWE9eFd0aNKrfveCAseXd9kj1v9oSBKJ4HWTbaiZDWg8mhSMw3ANGPpcqy7n9uQ9pe6ucO+1uANR6aCN1F161gLJD/GQqmLM3NFjdVy0DNlDdX3Ih6mgTA+f3iQAHi/zHNgbsroVrFz731JuyaL6Z1/+CJIDCghhOo6iii4LuUQQ5KVXXfCgVpj2Y4YIvQc3IIeqVWu8RfCNghKSpzXbiAKu5G9LicCDfqe5Cu1ugWS1awWw/AV2FPPViXa9bZqtUa6ayeW+Ow8vfPfVlgw/VRcNl m1QOzpp6 k8S+LgJNMi7cKidzrdrCTgy7gZG++D5dHsy5Z7mywQtNELCkvWGaQIQtVGbuJW3Z4NWZD2hdfN7NxrLwKYenyVusqCiB/yJfgIXG6JJ7k6W1FC8x6ixzlW5/p3Mbg5h0YPCNJNIO04UOYgvJqfWXAf3QzQTbD6SCtKzpFggYEU+2Fkr6C4VK00uUlHewQESGuCJA9m0nLOyzqayKLDVGAGntF+Sg0mkZJYkn3SKbA2I4pbeWbVB24b2UOZTUi2TxywmnfdH+UyzvE4M5+WmlbOwz11+RIqGW7MBLsXDw/4dM1iVHbL3WULDO6eGv/esVZ4d6HhPBfhriqSpbqTtWjnS5qWxiMBZYhZHgwT4EoxXyYQcSVvWa0y0228nGbe+jDiifBpOih5GAWNOfRM3FyB6Oq71l5AClLi4lT9UqSZ0IkPeO2sRmS1m+goMPshU1JgzykCaGjMKxcnzE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000069, 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 Fri, Mar 14, 2025 at 4:58=E2=80=AFPM Maciej Wieczor-Retman wrote: > > >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. > > Thanks :) > > I've came up with a theoretical issue for the following dense series that= might > happen if there is some racing but I'll have to experiment if it actually > happens. As long as it doesn't lead to false positive reports or crashes in the KASAN runtime - I think it should fine.