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[216.160.65.90]) by smtp.gmail.com with ESMTPSA id o26sm7440028pfp.219.2020.07.24.14.23.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jul 2020 14:23:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=7IhsA8lpB2O9xmXjvFVCcN+db4XOS/692WwIKQyfJAk=; b=DUf2UV+EbTaIA3b39gYaXsHl/MlF6i404pKAbbZbANXBWh+SXY1ymnO1RVxrO4MTWc jfNd5hTODWTtxQbsgtB55zQs6//QdWRvCaXBaNNVYX1NlteWy1iGngUDEjf0I1J1JR2C qhMU1V97Xw7DWGfdnjjMBe6/3++2VJ0jA5ZX46vIqGHE6rwjgBD/9MudcyKgRn3iiZc7 XbBGGtK1GoBSluJSgTF0GHAEpkfoOzf+jIX+WFLjtpDM8ZWvSXO2u1Q8pryrFmFW8ffr 02weBShd/uTWAjqU/CM4RrL6M39v/S/2uQ76N/8lCcTBJDCeZxYydVnq3klKHOMdFN0J EyNQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=7IhsA8lpB2O9xmXjvFVCcN+db4XOS/692WwIKQyfJAk=; b=GOoksAu8UNCx3Cekn/BSkJniCvv25EX8v9U/ECTu5mLlkLnDznYMcuq5dnNlqk6XAM iX9lOoXmf3uMT+zcY7MYv8O3zXR/Qi4j3yRVpqZmfYC408iJu+2mTqdg/6DA/II0Bt+q 5jMmHGecbLAdidEbCwhz4+mVxPINXYl1DzWCInp4bDZwHmCRUde2nYAaMSJ13mjgzFe3 esCYlHSsTMFSAacDbEdUctwzz6GFxWdfrw6LDwXlJHb8BcJ0WpTZFfLyaolKGrVoisHu 8fV+e5tIxIHIDZ1uf6RwBG/10YdaRAsOoOlsdPkaX3i49vMoOC55DIQpeRmpi1Sdh/YU 22cw== X-Gm-Message-State: AOAM531dnfWlyhQJU/99m6iDJD3u/qjF73eAYKQwRRHc+hIpHWsQ7iTW 1x7/fAmqkRRIrA7QjPaG49fiaG2puNM= X-Google-Smtp-Source: ABdhPJySl2eOxfqP7uNgiJTUmehPrmzj/cAWJYY8GmGrooQlnZUddr+ZyqVqGmqEJ+DvZZMt/e/FGg== X-Received: by 2002:a17:902:9682:: with SMTP id n2mr9612336plp.11.1595625796698; Fri, 24 Jul 2020 14:23:16 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH] linux-user: Ensure mmap_min_addr is non-zero Date: Fri, 24 Jul 2020 14:23:14 -0700 Message-Id: <20200724212314.545877-1-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::1042; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x1042.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alex.bennee@linaro.org, laurent@vivier.eu, John Paul Adrian Glaubitz Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @linaro.org) Content-Type: text/plain; charset="utf-8" When the chroot does not have /proc mounted, we can read neither /proc/sys/vm/mmap_min_addr nor /proc/sys/maps. The enforcement of mmap_min_addr in the host kernel is done by the security module, and so does not apply to processes owned by root. Which leads pgd_find_hole_fallback to succeed in probing a reservation at address 0. Which confuses pgb_reserved_va to believe that guest_base has not actually been initialized. We don't actually want NULL addresses to become accessible, so make sure that mmap_min_addr is initialized with a non-zero value. Buglink: https://bugs.launchpad.net/qemu/+bug/1888728 Reported-by: John Paul Adrian Glaubitz Signed-off-by: Richard Henderson Acked-by: Laurent Vivier Tested-by: John Paul Adrian Glaubitz --- linux-user/main.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/linux-user/main.c b/linux-user/main.c index 3597e99bb1..75c9785157 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -758,14 +758,26 @@ int main(int argc, char **argv, char **envp) =20 if ((fp =3D fopen("/proc/sys/vm/mmap_min_addr", "r")) !=3D NULL) { unsigned long tmp; - if (fscanf(fp, "%lu", &tmp) =3D=3D 1) { + if (fscanf(fp, "%lu", &tmp) =3D=3D 1 && tmp !=3D 0) { mmap_min_addr =3D tmp; - qemu_log_mask(CPU_LOG_PAGE, "host mmap_min_addr=3D0x%lx\n"= , mmap_min_addr); + qemu_log_mask(CPU_LOG_PAGE, "host mmap_min_addr=3D0x%lx\n", + mmap_min_addr); } fclose(fp); } } =20 + /* + * We prefer to not make NULL pointers accessible to QEMU. + * If we're in a chroot with no /proc, fall back to 1 page. + */ + if (mmap_min_addr =3D=3D 0) { + mmap_min_addr =3D qemu_host_page_size; + qemu_log_mask(CPU_LOG_PAGE, + "host mmap_min_addr=3D0x%lx (fallback)\n", + mmap_min_addr); + } + /* * Prepare copy of argv vector for target. */ --=20 2.25.1