From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7762130AEB; Sun, 26 May 2024 09:43:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716716620; cv=none; b=dv74DE4yUjyJvdlGsgBYyGD6KQB/Feps34rsNKLjL1pSxBa9Mo8tEVKC4aPV3pJ+rzw2pLPmWTmQewFYiFBMPMWgnwU53sPKIwtPPVL0JGMTVbtetJhqKcDFVtuljn/QFsR+XCuFQN9DD0vTnA7m77LN3s85AJ8TYbmejKs2mqI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716716620; c=relaxed/simple; bh=8M2a9IXtQtKWm46K1pN791UcrKjl7qfSLlHLkSIFFNA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r9IdpKADXr7gA1tQ3tdTV2Khbxc7bx8+O7yOOiqHuBOHd7im7ZviL0QtdJde2DlDy6Nic18oYDS46/yEIi7g36UJRKdbvreSO4DWBn2FcFsCAe/oFB47sWtFtpIBnC/HiJswMbt4cxqvbdq18vhyDLZT/DXT9MK7VkGVZaacoK8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XwQd1XHc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XwQd1XHc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD3FBC32781; Sun, 26 May 2024 09:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716716619; bh=8M2a9IXtQtKWm46K1pN791UcrKjl7qfSLlHLkSIFFNA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XwQd1XHcK6DNpyzl4hOKUgDvzSmpj3vQH/2UXK5bXNppI5AqEUXDOPmaqY9iOUZBP gN9zxaCvd8R7+1P3hRGFD2Ycu/Q6O3eVYbIIUY3OhL2F0wZ9grF8JYdzN3Jqytux20 gZucp4c8vIBMVAyLbutnyANN9nQWDfTTO1xrP06drvFoefPNzBsvsk/JH7DlVAOskA uaS32FMOl911dleMVZ8JguLmz8K2YLJRUC0Kah/x39XYKqXofugMomvM/Qp++glYZa hcUf/rqZaYaZUbaMDn2o82TgKdk6lM2KF/Lietb6hAj658DuTilz6hYkqir9PA4CuX uDdheaOaxoGXA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kees Cook , y0un9n132@gmail.com, Sasha Levin , viro@zeniv.linux.org.uk, brauner@kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.15 6/7] binfmt_elf: Leave a gap between .bss and brk Date: Sun, 26 May 2024 05:43:26 -0400 Message-ID: <20240526094329.3413652-6-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240526094329.3413652-1-sashal@kernel.org> References: <20240526094329.3413652-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.159 Content-Transfer-Encoding: 8bit From: Kees Cook [ Upstream commit 2a5eb9995528441447d33838727f6ec1caf08139 ] 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: Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ Link: https://lore.kernel.org/r/20240217062545.1631668-2-keescook@chromium.org Signed-off-by: Kees Cook Signed-off-by: Sasha Levin --- fs/binfmt_elf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 30379c33ad20c..932141c93f3e3 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1289,6 +1289,9 @@ 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); -- 2.43.0