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Fri, 08 Sep 2023 08:43:46 -0700 (PDT) Received: from smtpclient.apple ([2601:189:8480:9a90:2102:7c79:a2b0:6525]) by smtp.gmail.com with ESMTPSA id pj48-20020a05620a1db000b0076d9f2d4fabsm667235qkn.15.2023.09.08.08.43.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Sep 2023 08:43:46 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.600.7\)) Subject: Re: Memory protection keys: Signal handlers crash if pkey0 is write-disabled From: Robert Kueffner In-Reply-To: <4c49c85a-2b2e-e408-534d-586f06a8e485@intel.com> Date: Fri, 8 Sep 2023 11:43:34 -0400 Cc: Kyle Huey , Dave Hansen , Thomas Gleixner , Borislav Petkov , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <4c49c85a-2b2e-e408-534d-586f06a8e485@intel.com> To: Dave Hansen X-Mailer: Apple Mail (2.3731.600.7) X-Rspamd-Queue-Id: 7DF3212000B X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: j4ihz1w1ygbtbm4qqhzfc8gpjos6xky4 X-HE-Tag: 1694187827-380759 X-HE-Meta: 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 D7kQyRNG 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005521, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > There are tons of complicated ways to fix this. But the easiest way = is > just to say that you need to keep PKRU set so that the signal frame = can > be written at any time. Just for completeness sake, the signal frame was actually written = successfully since I moved the stack pointer to pkey-1 associated memory = before any exceptions, details in unix.stackexchange I = posted in the = beginning. And it=E2=80=99s probably that the kernel wants to write something else = into pkey-0 associated memory.=20 I understand that there is no easy solution, so my idea of isolating a = user from corrupting pkey-0 memory is probably moot. Thanks Dave, that helped me a lot to understand the problem=