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c=relaxed/simple; d=kernel.org; s=k20201202; t=1690878458; bh=KzvQJSYl9zliORTATgBPPvvWaET21XrF4cyjVIv9/XI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FZv0LIEbh+eOtxTtda3mi1G/HakIbe4Ec/6Cnmn9LUdCI9FrOiksmCTzlNNxzlBT4 MIXgNCSE3fyG7gBR5M5LOaV2UqtKnz2wytJDF/fHQqQV/hNxSLBaWToD6oTaw1NMRd +SIbBEMPRFEKmu2jycm5AbpsPeS4ZHVtztmmGOXbgoPPsZ80Dgj7wWuwDRLsUK0Z4l lFcVJoEbOn89u6D2oojaW5lWSBCHM+w3WZkqKSPCPB7Dl4f5cJ6OqhZ+35nM4vJ78G vP5U4ShZUHWBxh+G6+anK9+8wSAY23SydlfQLmHlgbScPb2Uawy59U4JhVgpda0KI/ 7+X51JArLXGog== Date: Tue, 1 Aug 2023 09:27:31 +0100 From: Will Deacon To: Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Baoquan He , Uladzislau Rezki , linux-fsdevel@vger.kernel.org, Jiri Olsa , Mike Galbraith , Mark Rutland , wangkefeng.wang@huawei.com, catalin.marinas@arm.com, ardb@kernel.org, David Hildenbrand , Linux regression tracking , regressions@lists.linux.dev, Matthew Wilcox , Liu Shixin , Jens Axboe , Alexander Viro , stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/kcore: reinstate bounce buffer for KCORE_TEXT regions Message-ID: <20230801082729.GA26036@willie-the-truck> References: <20230731215021.70911-1-lstoakes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230731215021.70911-1-lstoakes@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7F272180004 X-Stat-Signature: 59bdmzz1yzqbenqicpqx655fhh5pqogw X-HE-Tag: 1690878460-986427 X-HE-Meta: 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 tYSDXhcP KqAsU3xu5hSKIgFoJTNeC9WchQXmpXtpNVVoR5LLSHk5kWvSdsd6fZ0UaGHcd3ghJdUwqqKa9rYoU3x6XHFD/3r6qWvIP81Y7Gr5XE3lrz1u1y+oUeS4XUmZik+ubOrpyCfRXcAkwW9+0brrXJAytIq7+sXLpyh+Yparu0QysG0K7bmr655g144hatbJQl3ul19L5sLZygdqICxQ5E8IQ5W1rebZZSiADhQXwK84JGZCujEivzsxGxzBhL7RDycymbLY1wWTOzHqPESCuX3aH13tDr0Z8kIpmpZn/Iy9nzVLsFLw03AG2nRfiJtcBcKLxpnQPx/jn1ohrPWR1qCm8Q7imBsWgm09tKF2QegWGluGCwfCLUf1yPea8nJQ5OdPx7Co2c8U2RIbif1WrdZ8gPqOk9qWvyhajaERC 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, Jul 31, 2023 at 10:50:21PM +0100, Lorenzo Stoakes wrote: > Some architectures do not populate the entire range categorised by > KCORE_TEXT, so we must ensure that the kernel address we read from is > valid. > > Unfortunately there is no solution currently available to do so with a > purely iterator solution so reinstate the bounce buffer in this instance so > we can use copy_from_kernel_nofault() in order to avoid page faults when > regions are unmapped. > > This change partly reverts commit 2e1c0170771e ("fs/proc/kcore: avoid > bounce buffer for ktext data"), reinstating the bounce buffer, but adapts > the code to continue to use an iterator. > > Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data") > Reported-by: Jiri Olsa > Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava > Cc: stable@vger.kernel.org > Signed-off-by: Lorenzo Stoakes > --- > fs/proc/kcore.c | 26 +++++++++++++++++++++++++- > 1 file changed, 25 insertions(+), 1 deletion(-) Tested-by: Will Deacon I can confirm this fixes the arm64 issue reported by Mike over at [1]. Cheers, Will [1] https://lore.kernel.org/r/b39c62d29a431b023e98959578ba87e96af0e030.camel@gmx.de