From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EEE8327EC80 for ; Sun, 15 Feb 2026 06:47:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771138049; cv=none; b=lyzw3PIXVQvdUPznNxrR6RH4K5VEkRTxHQj/6WpLUI5XXWDKAQ5zAdVXNEMzSJn78m3hoKbAObqhZvWo+pr+5i/Sq+r/3Uc21kXtRK0scrEAuoft0WopQAa+Z9u/iMSL7eCSAm94WGhtznxm4A04AEZVsUX0FoQBkUvWJhvsrW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771138049; c=relaxed/simple; bh=Li2C5wEg3QVoAnSKgUm9f8v7M+2VmXqH7O8tRmrVvtw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=G03fGiPcGLXSNP0lAOT4C8WG2HjeI0TRqRp0Dqn0hRCycEKCJTM+BbgoTrwVPEzRCtEvar5L86Olv70QQ2W6vO4oMnPOvXpkF+3GotVLmTv9gr1kcKJXappZjrouvzfxdGtoXGQ5Dz3TfaihfhEwC30pxTYbjS3OhN3kYKtbNNc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Pd5ZgntW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Pd5ZgntW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E93C7C4CEF7; Sun, 15 Feb 2026 06:47:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771138048; bh=Li2C5wEg3QVoAnSKgUm9f8v7M+2VmXqH7O8tRmrVvtw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Pd5ZgntW4T22oD9B6EVv91jD12lpMZXLWz+cL8hG1AwF19lPGgfkoXUoXbhlDIU27 tAPOQpRHxN715E4CEr8c9gxYCJJ7FkcPZtB5byjVGSvmnBoO2hLDU97+48+eXWr/UF bdZ9KeBJxHaZ1GaOyMjUiM/qoOCuyu6cGjNdr+pvajgoJhIrXQknnRbsxpP+RAmvXi 9ewgdGFvs/CKyDlHXHAWVR83pRwObf3SwpvOU8074MeIWxyKdC+OdvsXMDe6zEV+O8 /0Xa+/cYWEsn8ihgTIVOR6/3RAMWVkEcUAqgbUhi6rpEym0K5O+vXmYu9EFOAWoOE/ piw17Eq1Vwg7Q== Date: Sun, 15 Feb 2026 08:47:21 +0200 From: Mike Rapoport To: Marco Elver Cc: Alexander Graf , Pasha Tatashin , Pratyush Yadav , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com Subject: Re: [PATCH] kho: validate order in deserialize_bitmap() Message-ID: References: <20260214010013.3027519-1-elver@google.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260214010013.3027519-1-elver@google.com> Hi Marco, On Sat, Feb 14, 2026 at 01:57:51AM +0100, Marco Elver wrote: > The function deserialize_bitmap() calculates the reservation size using: > > int sz = 1 << (order + PAGE_SHIFT); > > If a corrupted KHO image provides an order >= 20 (on systems with 4KB > pages), the shift amount becomes >= 32, which overflows the 32-bit > integer. This results in a zero-size memory reservation. > > Furthermore, the physical address calculation: > > phys_addr_t phys = elm->phys_start + (bit << (order + PAGE_SHIFT)); > > can also overflow and wrap around if the order is large. This allows a > corrupt KHO image to cause out-of-bounds updates to page->private of > arbitrary physical pages during early boot. > > Fix this by adding a bounds check for the order field. > > Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation") > Signed-off-by: Marco Elver > --- > kernel/liveupdate/kexec_handover.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index b851b09a8e99..ec353e4b68a6 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -463,6 +463,11 @@ static void __init deserialize_bitmap(unsigned int order, > struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap); > unsigned long bit; > > + if (order > MAX_PAGE_ORDER) { Preserved order can be larger than MAX_PAGE_ORDER. Let's make 'sz' unsigned long and add checks that calculations won't overflow. > + pr_warn("invalid order %u for preserved bitmap\n", order); > + return; > + } > + > for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) { > int sz = 1 << (order + PAGE_SHIFT); > phys_addr_t phys = > -- > 2.53.0.335.g19a08e0c02-goog -- Sincerely yours, Mike.