From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 81CA44E324C; Thu, 17 Sep 2026 15:50:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660222; cv=none; b=rUOSGh3YsfRBszsY0F5j756GghAw6jsvi/FqAorXMC9gAXbEyThubHRIihQ/C2yn+qrEC5QMgeNgNlti8bGfki/7VIwwJUg8Zhxpa9siale6+f9uSUp/E2HSLNJELR6+FRorRyd+sKZ5xH6gxwJayOf80TqPxa2awzG/UE+aGN0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660222; c=relaxed/simple; bh=axjZsEZM0oef55Ha5FbD8LAtj0FH3TjdZKa0v7n16GU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gUJkibEbEcyof2sxaLxk851iqkjswfrlZ7FYainlV6onS1nh3HiXi89K0UF4Si4bg2Ie8q5L5xWIzGCMJhq5etIeHeS+sZLMfwcUrcoZtyz0hg4fwhFgvj6y2UdaXfwuIizQECD13u8d240pMY7SNYJNls+EVAcYvH1l5K9yREc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XR+Q00rX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XR+Q00rX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7EA231F00898; Thu, 17 Sep 2026 15:50:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789660218; bh=o7VuY7NMKBTbb+aPNLGZA1utDhJ4o9hQOB4zENc5xqk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XR+Q00rXAbGJu9AJbWx1ECGpFBWKdxSQ1vOdVP3aQRb9fJBN6CrZOlHMR7skn6dHY 9zOdms5VaqiU2uQyZM1xfVGwesSqM8sjHWFhAO8moFmlyoVwrQmnmgbYEDfZeaa7rx PGCD9ebhDZ/PP24IEM9DehnRF2YJACgCNp+QN6Y0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sashiko , "Masami Hiramatsu (Google)" , Sang-Heon Jeon Subject: [PATCH 7.2 518/733] bootconfig: Fix integer overflow in initrd size check Date: Thu, 17 Sep 2026 16:13:46 +0100 Message-ID: <20260917151405.060673667@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Masami Hiramatsu (Google) commit 7812d6dab0698001e50e8c2f901e17da3eb6f429 upstream. Sashiko reported that in get_boot_config_from_initrd(), a crafted initrd with a huge bootconfig size (such as 0xFFFFFFFF) can cause the pointer arithmetic: data = ((void *)hdr) - size; to wrap around on 32-bit systems (or when pointer subtraction overflows). Because data wraps around, the subsequent bounds check: if ((unsigned long)data < initrd_start) evaluates to false, bypassing the check. The kernel then calls xbc_calc_checksum(data, size), which attempts to read 4GB of memory, hitting unmapped pages and triggering a fatal kernel page fault during early boot. Furthermore, on 64-bit systems with an initrd > 4.29 GB, an unbounded 32-bit size can similarly bypass the initrd_start check. Fix this by: 1. Ensuring the initrd is at least large enough to contain the bootconfig footer and verifying hdr is within the initrd bounds. 2. Checking that size does not exceed XBC_DATA_MAX and does not exceed the available space between initrd_start and hdr before performing pointer subtraction. Link: https://lore.kernel.org/all/178905333479.213925.1358412668943562406.stgit@devnote2/ Fixes: de462e5f1071 ("bootconfig: Fix to remove bootconfig data from initrd while boot") Cc: stable@vger.kernel.org Reported-by: Sashiko Closes: https://lore.kernel.org/all/20260910010137.EE0431F000FF@smtp.kernel.org/ Assisted-by: Antigravity:gemini-3.8-flash Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Sang-Heon Jeon Signed-off-by: Greg Kroah-Hartman --- init/main.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) --- a/init/main.c +++ b/init/main.c @@ -276,7 +276,8 @@ static void * __init get_boot_config_fro u8 *hdr; int i; - if (!initrd_end) + if (!initrd_end || initrd_end < initrd_start || + initrd_end - initrd_start < BOOTCONFIG_MAGIC_LEN + 8) return NULL; data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; @@ -293,16 +294,26 @@ static void * __init get_boot_config_fro found: hdr = (u8 *)(data - 8); + if ((unsigned long)hdr < initrd_start) + return NULL; + size = get_unaligned_le32(hdr); csum = get_unaligned_le32(hdr + 4); - data = ((void *)hdr) - size; - if ((unsigned long)data < initrd_start) { - pr_err("bootconfig size %d is greater than initrd size %ld\n", + if (size > XBC_DATA_MAX) { + pr_err("bootconfig size %u is greater than max size %d\n", + size, XBC_DATA_MAX); + return NULL; + } + + if (size > ((unsigned long)hdr - initrd_start)) { + pr_err("bootconfig size %u is greater than initrd size %lu\n", size, initrd_end - initrd_start); return NULL; } + data = ((void *)hdr) - size; + if (xbc_calc_checksum(data, size) != csum) { pr_err("bootconfig checksum failed\n"); return NULL; @@ -405,12 +416,6 @@ static void __init setup_boot_config(voi return; } - if (size >= XBC_DATA_MAX) { - pr_err("bootconfig size %ld greater than max size %d\n", - (long)size, XBC_DATA_MAX); - return; - } - ret = xbc_init(data, size, &msg, &pos); if (ret < 0) { if (pos < 0)