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[23.128.96.18]) by mx.google.com with ESMTP id u8si1561093edp.357.2020.06.11.02.22.37; Thu, 11 Jun 2020 02:22:59 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727119AbgFKJTy (ORCPT + 99 others); Thu, 11 Jun 2020 05:19:54 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:43309 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727039AbgFKJTw (ORCPT ); Thu, 11 Jun 2020 05:19:52 -0400 Received: from ip5f5af183.dynamic.kabel-deutschland.de ([95.90.241.131] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jjJN9-0007JQ-NC; Thu, 11 Jun 2020 09:19:43 +0000 Date: Thu, 11 Jun 2020 11:19:42 +0200 From: Christian Brauner To: Kees Cook Cc: Sargun Dhillon , containers@lists.linux-foundation.org, Giuseppe Scrivano , Robert Sesek , Chris Palmer , Jann Horn , Greg Kroah-Hartman , Daniel Wagner , linux-kernel@vger.kernel.org, Matt Denton , John Fastabend , linux-fsdevel@vger.kernel.org, Tejun Heo , Al Viro , cgroups@vger.kernel.org, stable@vger.kernel.org, "David S . Miller" Subject: Re: [PATCH v3 1/4] fs, net: Standardize on file_receive helper to move fds across processes Message-ID: <20200611091942.jni2glnpmxisnant@wittgenstein> References: <202006031845.F587F85A@keescook> <20200604125226.eztfrpvvuji7cbb2@wittgenstein> <20200605075435.GA3345@ircssh-2.c.rugged-nimbus-611.internal> <202006091235.930519F5B@keescook> <20200609200346.3fthqgfyw3bxat6l@wittgenstein> <202006091346.66B79E07@keescook> <037A305F-B3F8-4CFA-B9F8-CD4C9EF9090B@ubuntu.com> <202006092227.D2D0E1F8F@keescook> <20200610081237.GA23425@ircssh-2.c.rugged-nimbus-611.internal> <202006101953.899EFB53@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <202006101953.899EFB53@keescook> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 10, 2020 at 07:59:55PM -0700, Kees Cook wrote: > On Wed, Jun 10, 2020 at 08:12:38AM +0000, Sargun Dhillon wrote: > > As an aside, all of this junk should be dropped: > > + ret = get_user(size, &uaddfd->size); > > + if (ret) > > + return ret; > > + > > + ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size); > > + if (ret) > > + return ret; > > > > and the size member of the seccomp_notif_addfd struct. I brought this up > > off-list with Tycho that ioctls have the size of the struct embedded in them. We > > should just use that. The ioctl definition is based on this[2]: > > #define _IOC(dir,type,nr,size) \ > > (((dir) << _IOC_DIRSHIFT) | \ > > ((type) << _IOC_TYPESHIFT) | \ > > ((nr) << _IOC_NRSHIFT) | \ > > ((size) << _IOC_SIZESHIFT)) > > > > > > We should just use copy_from_user for now. In the future, we can either > > introduce new ioctl names for new structs, or extract the size dynamically from > > the ioctl (and mask it out on the switch statement in seccomp_notify_ioctl. > > Yeah, that seems reasonable. Here's the diff for that part: > > diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h > index 7b6028b399d8..98bf19b4e086 100644 > --- a/include/uapi/linux/seccomp.h > +++ b/include/uapi/linux/seccomp.h > @@ -118,7 +118,6 @@ struct seccomp_notif_resp { > > /** > * struct seccomp_notif_addfd > - * @size: The size of the seccomp_notif_addfd datastructure > * @id: The ID of the seccomp notification > * @flags: SECCOMP_ADDFD_FLAG_* > * @srcfd: The local fd number > @@ -126,7 +125,6 @@ struct seccomp_notif_resp { > * @newfd_flags: The O_* flags the remote FD should have applied > */ > struct seccomp_notif_addfd { > - __u64 size; > __u64 id; > __u32 flags; > __u32 srcfd; > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > index 3c913f3b8451..00cbdad6c480 100644 > --- a/kernel/seccomp.c > +++ b/kernel/seccomp.c > @@ -1297,14 +1297,9 @@ static long seccomp_notify_addfd(struct seccomp_filter *filter, > struct seccomp_notif_addfd addfd; > struct seccomp_knotif *knotif; > struct seccomp_kaddfd kaddfd; > - u64 size; > int ret; > > - ret = get_user(size, &uaddfd->size); > - if (ret) > - return ret; > - > - ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size); > + ret = copy_from_user(&addfd, uaddfd, sizeof(addfd)); > if (ret) > return ret; > > > > > > ---- > > +#define SECCOMP_IOCTL_NOTIF_ADDFD SECCOMP_IOR(3, \ > > + struct seccomp_notif_addfd) > > > > Lastly, what I believe to be a small mistake, it should be SECCOMP_IOW, based on > > the documentation in ioctl.h -- "_IOW means userland is writing and kernel is > > reading." > > Oooooh. Yeah; good catch. Uhm, that means SECCOMP_IOCTL_NOTIF_ID_VALID > is wrong too, yes? Tycho, Christian, how disruptive would this be to > fix? (Perhaps support both and deprecate the IOR version at some point > in the future?) We have custom defines in our source code, i.e. #define SECCOMP_IOCTL_NOTIF_ID_VALID SECCOMP_IOR(2, __u64) so ideally we'd have a SECCOMP_IOCTL_NOTIF_ID_VALID_V2 Does that sound ok? Christian