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 4B9173DA5CB for ; Fri, 12 Jun 2026 07:01:49 +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=1781247710; cv=none; b=d8VsqXAQlHjaknl74eWhY69lBothah9qgcByuU97aDhewikxqzdxltqNE/17Totv8/612Dot7OlAdtMyHXVeqGf9Fp2Q32bLK5bIXerYBLwW08HW7kNF9tkNzwFR+hFwNHci65Mk+ET8qd2VVvWl0x2Oqa1snxjkE1sT5RvdLb8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781247710; c=relaxed/simple; bh=Xt63ESHFurPqXzdPTYEh90d0MlRn+OEQ2IqU8aBUiKg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iAW+VqfpoxhLWhr+Aif1PLdSJNR5QFYfbdHMRRZbFNBF1zgcf4hx6o+kFPrfT3tv4bdYzoKWh5ytUzsD46aiUr+6toKgzgGoPLQf624CvrpkmvhyjaGCotLeuORZjDRSu+c5GBfmfdywYzE/rso7wsZyKsejS+Ho4dw2fk9Q8bU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=k1E2EpB1; 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="k1E2EpB1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 390011F000E9; Fri, 12 Jun 2026 07:01:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781247708; bh=xNfxQa1vwlWCvaXRQjFfS1B0XulfLE64TNHTVCMhrdo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=k1E2EpB1k5J7CBcJb6cpSck/EYkFoXJ/XOO8TUkLoNokPwku9IASWmksUIjVGuaRH Sij34V1NILT409NuiOjlzlPDCOF6WV5EPJzJoL1kBnHa9F0FmprR92wqyJZDi09Ir7 94eMUFLAmJRdhzNRpiPMevc2+a4sqlCWfkh0ad0B7H1CBFM7wbDYuOqlpb5+ciBe2a AL8VsQs40bUw6r7aiXBtZzfjX7RfbFq/dn4cfFzq/hXbtb9FbFDu5ZI92fvM3n5OMa OfpmLLwptq4WD9EWd9O/znlGB1UnsWh/GDlyLkYy5ehoDsF8692YWhg900C28x+Ya+ YQ4V0+5oJNb5w== Date: Fri, 12 Jun 2026 10:01:41 +0300 From: Mike Rapoport To: Pasha Tatashin Cc: Pratyush Yadav , Tarun Sahu , Andrew Morton , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/memfd_luo: validate serialized_data before conversion Message-ID: References: <2vxzmrx1qjuf.fsf@kernel.org> 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: On Thu, Jun 11, 2026 at 06:11:13PM +0000, Pasha Tatashin wrote: > On 06-11 17:28, Mike Rapoport wrote: > > On Thu, Jun 11, 2026 at 03:37:12PM +0200, Pratyush Yadav wrote: > > > On Thu, Jun 11 2026, Mike Rapoport wrote: > > > > > > > On Thu, Jun 11, 2026 at 10:30:03AM +0000, Tarun Sahu wrote: > > > >> In memfd_luo_finish() and memfd_luo_retrieve(), phys_to_virt() was called > > > >> on args->serialized_data before checking if the physical address is valid. > > > >> Since physical address 0 does not map to virtual NULL (due to direct > > > >> mapping offsets), the subsequent check 'if (!ser)' was ineffective at > > > >> catching a missing serialized_data, leading to unsafe dereferences later. > > > >> > > > >> Validate that args->serialized_data is non-zero before calling > > > >> phys_to_virt(). > > > >> > > > >> Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd") > > > >> Signed-off-by: Tarun Sahu > > > >> --- > > > >> mm/memfd_luo.c | 10 ++++++---- > > > >> 1 file changed, 6 insertions(+), 4 deletions(-) > > > >> > > > >> diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c > > > >> index 59de210bee5f..10f3983b0060 100644 > > > >> --- a/mm/memfd_luo.c > > > >> +++ b/mm/memfd_luo.c > > > >> @@ -397,10 +397,11 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args) > > > >> if (args->retrieve_status) > > > >> return; > > > >> > > > >> - ser = phys_to_virt(args->serialized_data); > > > >> - if (!ser) > > > >> + if (!args->serialized_data) > > > > > > > > We really should make args->serialized_data a KHOSER_PTR > > > > > > Hmm, that would also be a good idea. I suppose then it would be a better > > > to directly convert to using KHOSER_PTR() instead of this patch? > > > > Makes sense. > > I think we should systematically cover all phys_to_virt conversions > and add KOSHER_PTR() , instead of an ad-hoc approach of adding it as we > go. So, let's take this patch and do a series where we properly convert > everything and provide guidance for others to use going forward. It's too late for this patch for -rc1. So let's systematically convert all 4 or 5 direct phys_to_virt() conversions in the next cycle and be done with it. We have enough time to make it by -rc2. > Pasha -- Sincerely yours, Mike.