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 9B11254CF6C for ; Wed, 16 Sep 2026 23:53:42 +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=1789602823; cv=none; b=Jf58VpPm9r58TywxtkGNo3hh4mKZhA/oNXtKaXqFR6aCbvKb1eidA4L0Rs848lUa9pm0b4yM+U73uTmay3N5aibXP87uSMp4WLwYln2cwRZChx85LpE7iuPBorT2FvOrPTaJZgJW6nHXePgbIPRjUBdtH1Y+VbRdK8Yl64wxp04= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789602823; c=relaxed/simple; bh=o6PH+AxrP1eqxFaShGAcQgXT7erEdgzMbvEaYyPdrHA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HyyX+HcgD2u4o4wOuHWyM5AGFY1Dgin2uN42ObZRxhv93RHpUBImYlMs6vB9VYPNm1Xt+YBWEi5/N9439kf505nXMb56exl0GHZsi2slpH6Rcp16+BvZrrM1HbuE9sO0Pa76DuIupLlAvG3wMXzi87V3N8zI6hz+GojrNy+W89I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EEKu/HbF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EEKu/HbF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 962501F00893; Wed, 16 Sep 2026 23:53:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789602822; bh=PGjCKhWLVSSCAoidFZ5R91nuO0ClyfgtZWYv8wqeU0E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EEKu/HbFakSIRlYqlmRnPWTUABknalV5tIafVdgRopldqzicJF0jlqJblfsDyInoV YgM0dB6inBLNnbQA441bokz/67mmfAvJ6IWL4CSgHEppV6r0FXgLwB4KBdPkho6Jeo ljHVP5ZVMaTu0Vx8/1LnpYvzx7/i1fA7i5zFnvQd0ghdWqN3nzK8WN/LpcbHyLCFda FxEK6HVW0gykydT2lWiVdaiqWVq/A3tib1RxXrd5brj43ypRdDHI43guHXx7Q3yjjp CYiN9q0abOl9BAoe+yv5GucugezL/EtiVg7EaKvc1kmZ+wFXo19Co4mHfyQlcEW1oX sTgO930lH0k5A== From: Sasha Levin To: stable@vger.kernel.org Cc: "Masami Hiramatsu (Google)" , Sashiko , Sang-Heon Jeon , Sasha Levin Subject: [PATCH 6.1.y] bootconfig: Fix integer overflow in initrd size check Date: Wed, 16 Sep 2026 19:53:40 -0400 Message-ID: <20260916235340.3313629-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026091617-grudging-framing-3324@gregkh> References: <2026091617-grudging-framing-3324@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Masami Hiramatsu (Google)" [ Upstream commit 7812d6dab0698001e50e8c2f901e17da3eb6f429 ] 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 [ Adjusted context to preserve the existing u32 *hdr pointer and le32_to_cpu() header reads. ] Signed-off-by: Sasha Levin --- init/main.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/init/main.c b/init/main.c index 50b84f1f9ff38..76eeffa7310c1 100644 --- a/init/main.c +++ b/init/main.c @@ -275,7 +275,8 @@ static void * __init get_boot_config_from_initrd(size_t *_size) u32 *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; @@ -292,16 +293,26 @@ static void * __init get_boot_config_from_initrd(size_t *_size) found: hdr = (u32 *)(data - 8); + if ((unsigned long)hdr < initrd_start) + return NULL; + size = le32_to_cpu(hdr[0]); csum = le32_to_cpu(hdr[1]); - 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; @@ -400,12 +411,6 @@ static void __init setup_boot_config(void) 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) -- 2.53.0