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 2E0B041D111 for ; Wed, 16 Sep 2026 19:28:02 +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=1789586897; cv=none; b=tMm6BwTUtUnVIG59SjySN1xOdrk9/XaNYB4hN5LKBiZBy0/P8akjDFxUS3W/CLg1zca6wy6yJ3w0pBNvIjdchTfj9M4ReL2RchCiJ3LiDKR1WMGwBLAH+4W8Wsb70dLqbtZZ6QyPyElkrfBO+Y4yXwgSlsWhV3o+LtimP7DYoFg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789586897; c=relaxed/simple; bh=gChgCH3LnD4QJKZXuE1AdStJUz37xEIua5fIfjVViAY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HuFvvA1yEJKCxbHhfuijYA9+qiDOSV9FU50dP+7Px9Tp0t6YWyc1jmOUlOs021aeOPMYI+mz9VRcgPzrcYf93o3A5/q9hVrmVXE26W1wfV3wUB5AeTsqUxK4E36uoyKEt5YgXeRPc4/WpR4cSjeMcxJfMibwUfsAwulwk9LRP2U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oI9kpRHh; 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="oI9kpRHh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98CDA1F0089A; Wed, 16 Sep 2026 19:27:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789586879; bh=ydp37gFI8Dw1M/GcfO5hr6Y1W4iCNVHFlkYA5NsNEuE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=oI9kpRHh+pFLZFIZRfGJJj0ij/VdSBvfw/067gkCLBafV6jLIEUC73dabHY4lpLfj 6IHhtMOjbfy/Qc4DFc/nJs5LtRhdcKo83R5Z9htLo4dtcfULJZxh5WbLyik39dNk6f Tk9WiZWKR/xHP6UFfTay8EX5rfeaatTGkPiSBOQGj2Gn6YdqAKSWFGBGALtUBQaXoD mhIFvcUNukUwvNjeauY/nKkHw4KZJ4/7Qyb9ZCLOvwcAwMh/DFzAteK3MeJALNH6hN ZnHnvmAmN8UxzaeT63TKmUFOacL3HGtJkXOx1bsPm+mTCY4SBZW9QqRBqhNVXPMGva Pm7bMg978JgNA== From: Sasha Levin To: stable@vger.kernel.org Cc: "Masami Hiramatsu (Google)" , Sashiko , Sang-Heon Jeon , Sasha Levin Subject: [PATCH 6.18.y 2/2] bootconfig: Fix integer overflow in initrd size check Date: Wed, 16 Sep 2026 15:27:55 -0400 Message-ID: <20260916192755.2146743-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260916192755.2146743-1-sashal@kernel.org> References: <2026091615-curry-barracuda-b99e@gregkh> <20260916192755.2146743-1-sashal@kernel.org> 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 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 b254678062c72..a9f04c8caf7ec 100644 --- a/init/main.c +++ b/init/main.c @@ -273,7 +273,8 @@ 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; @@ -290,16 +291,26 @@ 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; @@ -402,12 +413,6 @@ 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