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Wed, 25 Oct 2023 12:23:04 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Andrey Konovalov Date: Wed, 25 Oct 2023 21:22:53 +0200 Message-ID: Subject: Re: [RFC] mm/kasan: Add Allocation, Free, Error timestamps to KASAN report To: Juntong Deng Cc: ryabinin.a.a@gmail.com, glider@google.com, dvyukov@google.com, vincenzo.frascino@arm.com, akpm@linux-foundation.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, "linux-kernel@vger.kernel.org" , "linux-kernel-mentees@lists.linuxfoundation.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CD46540029 X-Stat-Signature: tkwhp7ykjgdx5b6qomkr5pi1tw7cai8b X-HE-Tag: 1698261784-701213 X-HE-Meta: U2FsdGVkX18j6B9S1l0DTW226Jjdg1hc1wJVSY4cqZp0C5Hl4Myqn6DUaXgLsfe+D+hKQ1z51jzuBo5ZD8DcgegU6z1hN/stW3Xt93nweqpp7TnnQzydyRjww85rmk076nuPjMb707t/I1m2LXclL3EUmSxbjaKJ82tRAr3pdF5o/1BEar4WVamx4+3+JQQwLpAUDCd7kIlCZecZugxySY51sRoAICnc3xgIEqMVsrTXALXqJAgKmt3MrhJD1u9NpT9n4ImQ9+JAH3moNilmOstW27u1pmJggrm4OGjI2XvQT1O+/JApBlHOzSIpYRsmXhA7WMvn/ZP47I6bEAyu336G7bDmlbNKdsxp7FwYamvcpWQ04D9kGR1YzbkBG3Fsg3V4RzUh3sQlv2i20+EFWjYxfIf0t3NFfsAno6QbdBkn5ti/8tRm4W83Ov6KslTubrTKO2YnuwP1VnyNwaRvSaOIhYJgdYehynd5ok/rNof8C76fsYVt5B+SFawCCiCkHH5fjgjvr8Sl/dTaJ9EgIo/xWcnf1587ARi7kgHsjyDAuYPxGc+nbQaajJGKkTZ7hzs4SqFWh3n/4PRaGTomam2mCO2gR6ndo1QfDcfzCmy59hu7X4Me0i7im2XG3x9dODbNE1jTch+FktY+06rJ57NcYYK/4NRwi5EsrTI2Dtyp/mEBiqN8mKXLM+Qo+InH30skUGBlbu5CN8F6NgNDxKz9zsqig+LIpxnLxjmjWy0T39921UzJRA5q9T9aDyLQhytpbMJj7xhhHkfuYv+uUq4SkUUlM0qwmB4O2tE8fPqcCteAgO1r6DtIJfzCETgvS4P3fHF+IQfpGiC6ZkqhjEyKxOcCG94Wa0V+Wjlqc8Frt78Msrr19qrjvUL1Y4eGw9ioS/wdomUpN0jDkD3UuraS+wy6JnpeDrEaZ/43Zzg3mm7zau8V5lqZ29WH80TXsPDFEQgoLY2+QTuAb2G Um/Gdxug bllqpy8AtrBE2NWT/t/mLOfzsKkq7eYYxNulND3GB9PbLq2AWLTJcBAEJeUZof26RXFS+BipzACOX+a7BzHe4U4BTn//uhSLf13xVRK+y8DGzleIgkF9nry86JW3Zoj0hXwSeiemedhyvH0g1cqN/8nQr+EAh+s2s+XZ33oBm1THOIf+1YOoZWG6sPZp3M4/HScmSasv3sOzIFvyZOszlpncfVw12k8fZlIkFAQo5OOwSgnqsEc5aIgn+kBIqgUcHxWiQd1Gu/U/IQW4eXKm1sYiJgU3VDFVWMlQ2HQ1DxcckPnzAsFkPfyyjbnBVmPVzm7Fd9VrVRO/mYUk/wTIaf0Nnbo2cW/SUSohaq4Bt0aluPz+oXkOaLAVL7CMl7GJGwPearlS/l1QVA/drf4SO9PcELmUvPEaLM856J9kfQGdR9odhy8MtEUTCb2Y9k2tcJP8Nz01I0wCh5fY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.057399, 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, Oct 17, 2023 at 9:40=E2=80=AFPM Juntong Deng wrote: > > The idea came from the bug I was fixing recently, > 'KASAN: slab-use-after-free Read in tls_encrypt_done'. > > This bug is caused by subtle race condition, where the data structure > is freed early on another CPU, resulting in use-after-free. > > Like this bug, some of the use-after-free bugs are caused by race > condition, but it is not easy to quickly conclude that the cause of the > use-after-free is race condition if only looking at the stack trace. > > I did not think this use-after-free was caused by race condition at the > beginning, it took me some time to read the source code carefully and > think about it to determine that it was caused by race condition. > > By adding timestamps for Allocation, Free, and Error to the KASAN > report, it will be much easier to determine if use-after-free is > caused by race condition. An alternative would be to add the CPU number to the alloc/free stack traces. Something like: Allocated by task 42 on CPU 2: (stack trace) The bad access stack trace already prints the CPU number.