Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
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
Cc:     Albert Ou <aou@eecs.berkeley.edu>,
        Alexandre Ghiti <alexghiti@rivosinc.com>,
        Andrew Jones <ajones@ventanamicro.com>,
        Hugh Dickins <hughd@google.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Qinglin Pan <panqinglin2020@iscas.ac.cn>,
        linux-riscv@lists.infradead.org, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>,
        James Houghton <jthoughton@google.com>,
        Ryan Roberts <ryan.roberts@arm.com>
From:   Palmer Dabbelt <palmer@rivosinc.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        John Hubbard <jhubbard@nvidia.com>
Precedence: bulk


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 <palmer@rivosinc.com>