linux-kernel - Re: [PATCH] mm: riscv: fix an unsafe pte read in huge_pte

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Date:   Wed, 05 Jul 2023 16:38:27 -0700
From:   Palmer Dabbelt <palmer@...osinc.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        John Hubbard <jhubbard@...dia.com>
Cc:     Albert Ou <aou@...s.berkeley.edu>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Hugh Dickins <hughd@...gle.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Qinglin Pan <panqinglin2020@...as.ac.cn>,
        linux-riscv@...ts.infradead.org, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        James Houghton <jthoughton@...gle.com>,
        Ryan Roberts <ryan.roberts@....com>
Subject: Re: [PATCH] mm: riscv: fix an unsafe pte read in huge_pte_alloc()


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@...osinc.com>