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Wed, 05 Jul 2023 16:40:42 -0700 (PDT) In-Reply-To: <20230703190044.311730-1-jhubbard@nvidia.com> References: <20230703190044.311730-1-jhubbard@nvidia.com> Subject: Re: [PATCH] mm: riscv: fix an unsafe pte read in huge_pte_alloc() Message-Id: <168860030766.22647.15542339368600249770.b4-ty@rivosinc.com> Date: Wed, 05 Jul 2023 16:38:27 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Mailer: b4 0.13-dev-901c5 Cc: Albert Ou , Alexandre Ghiti , Andrew Jones , Hugh Dickins , Palmer Dabbelt , Paul Walmsley , Qinglin Pan , linux-riscv@lists.infradead.org, linux-mm@kvack.org, LKML , James Houghton , Ryan Roberts From: Palmer Dabbelt To: Andrew Morton , John Hubbard X-Rspamd-Queue-Id: 0C338C000D X-Rspam-User: X-Stat-Signature: 6b5uhwmfyo3g1t49xwt8qxq44kagp5ee X-Rspamd-Server: rspam01 X-HE-Tag: 1688600443-160274 X-HE-Meta: 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 0p7uhAzN fyAhnoRgxCHQ2vfRb35+C/wB7Yvm7sPa0ROG2OGv6tGv5kieDo8DSjj1LIuDzRDZNZVoEfSFpTZNg+A+4qcIYj8+JTdcJ9IHHDQcTUA2EYcZMTGbe/zl/x1TqHrQL5HLXk7N7orUBjIoM78u0mMiPb5qnQkJX8Xy/mwLatkc2DRyNjT+5IDMpK3pp0Wxao+VW+nkyb2fGrYjB62p7xnYyGgS9OelaK0dd1SMDI3OuW7cNwIo+wsgmAZOdb0zVCON3GrywbEidrCOZdq3yY7h3R3ayrRSkrMAcnBBXzDDN/mpKXFgepTx+6zKqaWynfNILuwstma43jZ/MrCXOBca63N97+89BLTAs4UIbaKaHaTq7Xqp3slp3T3IpNpWBUTWkF7Bg0NUYsM8cV0pf5Aiy7cL6DpTkVB8uyT2S31jCcb5W9CFTDHnw5txPgMI8G4SX4GrLmWBsNDOi55vBB2XSrXHbdFIola8h4RwTXoDekelNIOyZOPDD+g1YLM5VdsVF5m8UaqAz3RHwB3wZMpxnI1LrKTytCZBgFkwjBuKkZku54Q0KFvTzcHoxHg== 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 Mon, 03 Jul 2023 12:00:44 -0700, John Hubbard wrote: > The WARN_ON_ONCE() statement in riscv's huge_pte_alloc() is susceptible > to false positives, because the pte is read twice at the C language > level, locklessly, within the same conditional statement. Depending on > compiler behavior, this can lead to generated machine code that actually > reads the pte just once, or twice. Reading twice will expose the code to > changing pte values and cause incorrect behavior. > > [...] Applied, thanks! [1/1] mm: riscv: fix an unsafe pte read in huge_pte_alloc() https://git.kernel.org/palmer/c/62ba41d27612 Best regards, -- Palmer Dabbelt