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 D7F803F0AAC for ; Thu, 28 May 2026 13:11:51 +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=1779973912; cv=none; b=uSAjAeDy6B2mJaZ2HpF1q0uqiq02LPP1N49jN4UIB1AzlCM3CYuWDG3O8zCa+rPzdiMrhBSOS7JamTiPrOMgMZIo/hq6crenttKZi4ac05V4Y2xhVjko1J6bwi0u3vUqXT4gEra3xoNBhA5BUsKfPD4PuTlGDSg7/iexGuv/VvA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779973912; c=relaxed/simple; bh=zZiMmJH7Qc9jz2UF2536OqYvPgDuqidMdCJrlEjtsq8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VAH3cenpd8zyHGrqBnreL231kEJIB1FVybSq79OdF7hHKtzbYnshOITpGuLZK3lQ61mGi+FbCh572WNNOcsg/RfmBG7SEci7hAzwo9drcGtdOTo3kBDrkf7GTHi1/Eh4cD4nVBElkvmBowfluz9DtLxg/p31Q6gSh9Qunjh8lHI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OiY5Kxs2; 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="OiY5Kxs2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2AACA1F00A3A; Thu, 28 May 2026 13:11:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779973911; bh=VrpnDjUd1QiX7kPJn7TspldNReCZfbhP7mEDa/yWeoI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=OiY5Kxs2GV7tgu8Kq3IkS2SUr98NUb33Gwex3B73v3E9f5nE2xgBY2Qw4LPdiyOJf vuzhEGUwj6TbNEIbWnVqe05DVqCmzq6FE3wUnVP7bOMncHPVgKmjsJEO/Q8EWcziap xCUu2kgggG5hhXEnacE6dAFCQMxdUnIPTomJgcDij6uKjP7ZG1BFSsqJHHkkaH0V0j X1ajrOM1L5jgg6T8IZM24y9Q5kJLL/ZphHN/h2F+N4AJdRaw9wZzsDHzGLvqcbwaol r2K6HY4q65Eav1cB7Se7AriKHJsHmxmX6uA9HWb2NBUpmYhfOMO7jTh0/GDcNUmm+i mAz22JGspXxKQ== Date: Thu, 28 May 2026 14:11:45 +0100 From: Lorenzo Stoakes To: Mike Rapoport Cc: Andrew Morton , David Carlier , David Hildenbrand , Heechan Kang , "Liam R. Howlett" , Michael Bommarito , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] userfaultfd: refuse to __mfill_atomic_pte() for unsupported VMAs Message-ID: References: <20260527184751.4147364-1-rppt@kernel.org> <20260527184751.4147364-3-rppt@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: <20260527184751.4147364-3-rppt@kernel.org> On Wed, May 27, 2026 at 09:47:50PM +0300, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" > > __mfill_atomic_pte() unconditionally dereferences ops because there is an > assumption that VMAs that can undergo mfill_* operations are vetted on > registration and must have valid vm_uffd_ops. > > Add a guard against potential bugs and make sure __mfill_atomic_pte() bails > out if ops is NULL. > > Suggested-by: Lorenzo Stoakes > Fixes: ad9ac3081332 ("userfaultfd: introduce vm_uffd_ops->alloc_folio()") > Signed-off-by: Mike Rapoport (Microsoft) LGTM, so: Reviewed-by: Lorenzo Stoakes > --- > mm/userfaultfd.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index e5d2fb3ce2c1..2872c71bbf36 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -552,6 +552,11 @@ static int __mfill_atomic_pte(struct mfill_state *state, > struct folio *folio; > int ret; > > + if (!ops) { > + VM_WARN_ONCE(1, "UFFDIO_COPY for unsupported VMA"); > + return -EOPNOTSUPP; > + } > + > folio = ops->alloc_folio(state->vma, state->dst_addr); > if (!folio) > return -ENOMEM; > -- > 2.53.0 >