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 17CFD3C1D4A for ; Wed, 16 Sep 2026 22:46:44 +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=1789598809; cv=none; b=mQwflPJEXGGWxA5yXcWhsTvix2s8hWzTS6pwATsjPtWz83ADUqwAuUK88F2gHvhHN6jfMYDOXRJSw7b9+eX7wR8+E8urwYMKxHqGpxi3ptzA0hqGQb8rNCH/PF69ZuaJUZeypcy4dYUyTwwny7mPa2hX9k6dmaAg9r12SDS+HUo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789598809; c=relaxed/simple; bh=9yJasCiYaRf7RJYnO5TkFG76S9z43HiaKHxgBny6iAg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HUEEr0BW6w6EEhwdvbao7xNfDIO2c7rk5rlpTNLsiH/I66m4H8v4D1ujSvOB136n5+fdDtHu+ZXeBwC31kiJWNLhVzwxhj5SH9WAFsXzuqnzGMgdb93tfCaHiVQKQEVNebzcnDGccUKDdyIofFlBPAqzjqj5zTR+htW97UfembI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mqsuMymw; 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="mqsuMymw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE7BB1F00899; Wed, 16 Sep 2026 22:46:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789598803; bh=r6tUTEF5Sseky+tuDAtG16hbjlRhXN7vuVi9VvJ++As=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mqsuMymwt5rxOqqChYiEzh0m7znhBf4QCrCgTyp/UEApp0oahC4drdTsSe5awEmM3 baz68s92zs17JOt8kVfQhd3XPCsuZk5Sqe4VSibz+s9j9qBN1D7wY3kpG12BK58+8f rZVRUA8A+rmPLtY5HJPdcEbmfXySOxlU6CS527f9Xm0CSilUYFLIJKYY1nfsSfw2wB CleJfTRBowX9skn2hUL+V3hzlTdLGRK1KgSvXYSGiu/dv+6BpGxsbkIAWFvo/ZpfDE W9wocSiaA9gIVhHUo5XikLyk4PP+6vvwmE+at2BxmH90FjAz1JqqTICszUHDg1CAmZ sV4V9BqagzlMg== From: Sasha Levin To: stable@vger.kernel.org Cc: "Masami Hiramatsu (Google)" , Sashiko , Sang-Heon Jeon , Sasha Levin Subject: [PATCH 6.12.y] bootconfig: Fix integer overflow in initrd size check Date: Wed, 16 Sep 2026 18:46:41 -0400 Message-ID: <20260916224641.3199092-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026091616-ricotta-character-82bc@gregkh> References: <2026091616-ricotta-character-82bc@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 df9db4d47868a..638e16048cc3c 100644 --- a/init/main.c +++ b/init/main.c @@ -270,7 +270,8 @@ 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; @@ -287,16 +288,26 @@ 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; @@ -399,12 +410,6 @@ 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