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Peter Anvin" , Peter Zijlstra , Qi Zheng , Alexandre Ghiti , x86@kernel.org, Al Viro , Christian Brauner , Jan Kara , Eric Biederman , Christophe Leroy , Josh Poimboeuf , "Kirill A. Shutemov" , Rick Edgecombe , Brian Gerst , Bjorn Helgaas , Tony Battersby , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org Subject: [PATCH 1/2] x86: Increase brk randomness entropy on x86_64 Date: Fri, 16 Feb 2024 22:25:43 -0800 Message-Id: <20240217062545.1631668-1-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240217062035.work.493-kees@kernel.org> References: <20240217062035.work.493-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1595; i=keescook@chromium.org; h=from:subject; bh=J8yZ3FuS1LWrR5jVIrwba2SyB7GFZoxGQ5Gq7wzczYA=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBl0FFofylSSc0zctidXuws91GIZAfUD3EvfMTgD C7ILFWiQEWJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZdBRaAAKCRCJcvTf3G3A JuvKD/0YST+WQlVawQvhCb3pQXdND3wneO4rAAc1MIaPKKYFGzOMCeSQYBifV0JEeFHph1WsrQC n4+hCw/MTLwSm24DnSu1EEevAaPtL2voVeq16UMZrkG/yapEWn3+250s3daI8qSEHpaTs+lqmrY 20PeyS18a3NDnzD6VRtlc/Ud4NM4lTrD59tsR9Zypsk8QkTOW11SzkDOU36Vewr5lvz9WlASgCb uX115bQ6YNYuZQkpWi0z4MlnmeNcdOuQnupP0FwTKJDVMHrN+vvFac+rR68LNoQtHQMqb0yZKXr iaQfIX0RbdI1t7Ns/XMSdQQfLgvkslY3PnQ7KanuL/2iVQSA+qYKaUHT1q5rU9VB+w3Dck4Dmye Mw0zNvdQB8Y4A4EnGY6HYyO6ucLRSQtEfIuXbYYszYSq6wZmHI2F8gQrXTQN6dKrHavZBh6DOSY Ep4Xtnl5207P/j3tkJ2WlgxPesAECiupJebylL9V96dhr12EkUmNs83ixnDjhgIhd/q1C66ZLuD gOP5XrfxOIcEw0QQFj8sFRcjpHdAnouwZruQruo4ED1IAeSMX2ThvD6Di09uNBuIX4r27aUDkF4 PMMxi3r0jO2Iy/OhTCP2lOG3dtuz7BSAH3EaHzmxqr7QyGazjc6Mux/rumcsyyFjQTLaXMsCYg5 3MpCUeeX8WL+hxg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791126342497175598 X-GMAIL-MSGID: 1791126342497175598 In commit c1d171a00294 ("x86: randomize brk"), arch_randomize_brk() was defined to use a 32MB range (13 bits of entropy), but was never increased when moving to 64-bit. The default arch_randomize_brk() uses 32MB for 32-bit tasks, and 1GB (18 bits of entropy) for 64-bit tasks. Update x86_64 to match the entropy used by arm64 and other 64-bit architectures. Reported-by: y0un9n132@gmail.com Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ Signed-off-by: Kees Cook --- Cc: Jiri Kosina Cc: Geert Uytterhoeven Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: Qi Zheng Cc: Alexandre Ghiti Cc: x86@kernel.org --- arch/x86/kernel/process.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index ab49ade31b0d..45a9d496fe2a 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -1030,7 +1030,10 @@ unsigned long arch_align_stack(unsigned long sp) unsigned long arch_randomize_brk(struct mm_struct *mm) { - return randomize_page(mm->brk, 0x02000000); + if (mmap_is_ia32()) + return randomize_page(mm->brk, SZ_32M); + + return randomize_page(mm->brk, SZ_1G); } /* From patchwork Sat Feb 17 06:25:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 202577 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:693c:2685:b0:108:e6aa:91d0 with SMTP id mn5csp173544dyc; Fri, 16 Feb 2024 22:26:34 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCVlWGBPAIYKW+wh6/+sLLc4mMUspdW5DdcbMf7+lYZvQ7ST613gJ32suIKMQKy63iuNQYmoZeLXcKgBLP8MdPvv6fYi4Q== X-Google-Smtp-Source: AGHT+IFDH5w+67ziql8X35AKSDtpbdo/q5GgS0MP2xKMYrOOnrdwzOjJ5F3POwZdbvlHIm1sMRUF X-Received: by 2002:a17:902:7843:b0:1da:2a91:8c08 with SMTP id e3-20020a170902784300b001da2a918c08mr6309205pln.3.1708151194560; Fri, 16 Feb 2024 22:26:34 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1708151194; cv=pass; d=google.com; s=arc-20160816; b=p+/Q59Jj+dNhFOYVNXZaebRsehvm4FCvtTUxzVLh7YMmMXyn8yTZwn2G9P9c4EXZIt 7wwLhEN3l1vdXJ5HqL8tU7XBnqexRTtbSm1uQJvhzyQppMD60gvMLkm/pjkW5D10nZJe G1CaWEDlD4XAx4N4osHzi2BSevhYJcOo8sB2HX5NXSVZbFo/dt381mt3wYDmOJdJDRuJ qTc23YO4B0EnTAlUpAzhrjRNr5l8ZAHytYh+1VgmU6q/1vAHKOtV50+fgnprr2MuOByA BT8g/+Oix1Ar54KgXe8cnj3lys0upPjv70mELCRdOOo+4RFGdVygjOrs0Cw3KJF6gQyr +ewA== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:list-unsubscribe :list-subscribe:list-id:precedence:references:in-reply-to:message-id :date:subject:cc:to:from:dkim-signature; bh=E2RXdELjA1+Y5TPLiUTm0d2mhfp+RAxxenDK5Rv9UCY=; fh=rPeLNfqiFDVU1s1XEm3gdyWMG2ndkuDM/JMQcegZ5v4=; b=ijRbx6iE65/qMy9MTQVEdyBsaeALDiwiAhvV14XqNT3PGXTzbqwNVlOqgWFe+Ow6Ba 63YhMudEyDsl4rZ/Gr369zNysY3sTpH91S/w387SX3spQVP0nV8EA2GWdn1Nko7VLro8 15K/s+4dAx/qHz+BmAnGPkkpjBW8+UP55IxFi+Y5hWvcQLfTLeriAfTIpQYtq1uxUsbt +lzmG8GNkLuLeBF0yXd6HskFRpzvlrtx1UbWpfbkVM71DyI1vO+6naYmVMIGD3GDPVJj MWgtuOFslC0zhIwn3lsTpyvXdfZnsuewdAxMOGfdM+8Pkbp4mGQccqgcnj1aVc30t1Zq FmhA==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=PSM2Juy3; arc=pass (i=1 spf=pass spfdomain=chromium.org dkim=pass dkdomain=chromium.org dmarc=pass fromdomain=chromium.org); spf=pass (google.com: domain of linux-kernel+bounces-69706-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-69706-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org Received: from sv.mirrors.kernel.org (sv.mirrors.kernel.org. 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Shutemov" , Rick Edgecombe , Brian Gerst , Bjorn Helgaas , Tony Battersby , linux-kernel@vger.kernel.org, x86@kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH 2/2] binfmt_elf: Leave a gap between .bss and brk Date: Fri, 16 Feb 2024 22:25:44 -0800 Message-Id: <20240217062545.1631668-2-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240217062035.work.493-kees@kernel.org> References: <20240217062035.work.493-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1512; i=keescook@chromium.org; h=from:subject; bh=Y9GWQSNdeMe/TiCQJCjXENrVrfi7E3amSjOSWzM2S1o=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBl0FFoSMLWKnRZV/Xpg3nYIyPCuv0NWoUMuFI3f ssQMNwOx8mJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZdBRaAAKCRCJcvTf3G3A JvXFD/0ZGY+pv/RW0jEwUr/fOJKrMeYvRA+q8dAhwBU4yZf/9WvOK1OItaQt6erwqczIQcGDsKX RWFEhlQbXwgzOXrwCvEVU3X/MwTvOZFnZ0wTXOJZIuqX6uhvJuDZYq+kDfDixzSf+vvZ5N5gZBO TJzXBbBFV7TqO+okj4IS3xOJWZewgGjhNT8vbeQcPdzj69HDDkXXfpLkoSfygpZcWqlp9XDZiNy vXK3r7lesiRP3IhhoJj7l67XzCYktFTMcgxwx7uHCkePYddv5NSQpYuV1e3GrWYPneqbU/ta/RX cWwsnNmxh2abzRU47UKh05W/uYImIbey5l0CSZI/7QN6m152TAREIrmIXwl2k22fjZgwgd+Apv8 4oW4U/bqzoG9w1PMnHKDMQ9jsdEQB9hjMCKn8XCd+7Gv1wyNPPDXV5RFfLYuFJeaPMBdmXP7zFy E345+0/LhEK6UZl9XBsjpHxXtro8hrLNXyQJNR0dzipAEXd7VeizjMBrL4dibLwpq9Vt5GEwcbV rdHrk6W8yGkeyTm7dflKIXZxINWwAC8JEcnyTOaMiaSf+7Trt7zTSHdjJwqs75llY8Q2hwdTTG3 H4HQ8+CnaTwekWZMYV2AJy4oOxU2TWbO/56rrPwpm2xEE837qZM9Jz9EeaTLbA9t0NKKZotRk7n IeAJGDC3TTWSd+A== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791126346840204137 X-GMAIL-MSGID: 1791126346840204137 Currently the brk starts its randomization immediately after .bss, which means there is a chance that when the random offset is 0, linear overflows from .bss can reach into the brk area. Leave at least a single page gap between .bss and brk (when it has not already been explicitly relocated into the mmap range). Reported-by: y0un9n132@gmail.com Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ Signed-off-by: Kees Cook --- Cc: Jiri Kosina Cc: Geert Uytterhoeven Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: Eric Biederman Cc: Christophe Leroy Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org --- fs/binfmt_elf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 5397b552fbeb..7862962f7a85 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1262,6 +1262,9 @@ static int load_elf_binary(struct linux_binprm *bprm) if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && elf_ex->e_type == ET_DYN && !interpreter) { mm->brk = mm->start_brk = ELF_ET_DYN_BASE; + } else { + /* Otherwise leave a gap between .bss and brk. */ + mm->brk = mm->start_brk = mm->brk + PAGE_SIZE; } mm->brk = mm->start_brk = arch_randomize_brk(mm);