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 176854AB1A6; Thu, 10 Sep 2026 15:15:43 +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=1789053348; cv=none; b=UTm/9r0a5e0ozAJQXMU7P+15gihtSXBDoUPuQVhhxWqnn4GxjQudMG//PRowjz2byWNeSkHuU2vElWFssEKshZfs+kymSBHQes5SeKdznWKBolTaGj5834qXdgOkLrynFn8Icv56X0Rl6lo/iZDknaaJAwQ4xtrgxhzwcOJvzz4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789053348; c=relaxed/simple; bh=AGGTo8x6LltFZhyG3DBF2Ux8tH6OAROqJsckgOxCd+A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UySgINxhkU6R/v/3e/m7Yxm0xEfDVwRppUup9Sj+0sFmptg8JQQknXyNXHNqeBh8E/QLvnRrFXwv/I5W6o5rWT5pXJQJZWH1t3cGLP24+kPlwIXtEXupqxsbAjs6hzYhoZuVmRj9fUK2SdeTKiLyVLTCweJUD7ne7lWO0Wo9yEY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FDBCL2tH; 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="FDBCL2tH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 052FA1F000FF; Thu, 10 Sep 2026 15:15:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789053339; bh=tA/ppFhQxULDYYeN7C/s9VujISrGiMIKSwQKZxHHjbM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FDBCL2tHqsW9oRjEpTEy+uXVu3ZDkIJp0lI5+6ory7rtBb1FElTVIodOtuQ3qxSNN MqCHnhR0HwabviMf7YDef7IXy5mIyRRG9ZAuwjyTm86J+89Y/H2/oMwe1DwTbe71I2 tzDLFM+VLY11vL9NerNXciDimCbLRzc1kfSsSG4MqNQ8b/P9As/IZr5vRgWtGiDrZv SUjN2pqb3VrlYdJfH7r5ub2Dtj8borepDm/yZ6pEwGbvVkOhQAp7GiApesiEuVtMrZ XuueTVgLjpT2pET+b1EJ04KUx1hQL92G0cXTiePoah+C+0zoSrGpDTpGd1NJlnaJhU COUc4TeB1Jriw== From: "Masami Hiramatsu (Google)" To: Masami Hiramatsu , Andrew Morton , Breno Leitao , Christian Brauner , Thomas Gleixner , Ryan Roberts , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Douglas Anderson , Huacai Chen Cc: Mark Rutland , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Sang-Heon Jeon Subject: [PATCH v4 2/2] bootconfig: Fix integer overflow in initrd size check Date: Fri, 11 Sep 2026 00:15:34 +0900 Message-ID: <178905333479.213925.1358412668943562406.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178905331374.213925.295025394754459843.stgit@devnote2> References: <178905331374.213925.295025394754459843.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit From: Masami Hiramatsu (Google) 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. 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) --- Changes in v4: - Accurate the error message for size > XBC_DATA_MAX in get_boot_config_from_initrd(). - Remove redundant (and wrong) size >= XBC_DATA_MAX check from setup_boot_config(). --- init/main.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/init/main.c b/init/main.c index 2613d3f9b3ce..16749bb7a219 100644 --- a/init/main.c +++ b/init/main.c @@ -277,7 +277,8 @@ static void * __init get_boot_config_from_initrd(size_t *_size) 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; @@ -294,16 +295,26 @@ static void * __init get_boot_config_from_initrd(size_t *_size) 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; @@ -394,12 +405,6 @@ 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)