From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51C19C33C8C for ; Mon, 6 Jan 2020 14:31:11 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 18DBC2072E for ; Mon, 6 Jan 2020 14:31:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HfK7OGuv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18DBC2072E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52488 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ioTPS-0006d4-7C for qemu-devel@archiver.kernel.org; Mon, 06 Jan 2020 09:31:10 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37280) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ioTOe-0006Ab-9O for qemu-devel@nongnu.org; Mon, 06 Jan 2020 09:30:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ioTOc-0000Yg-Ay for qemu-devel@nongnu.org; Mon, 06 Jan 2020 09:30:19 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:22996 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ioTOc-0000Xz-5T for qemu-devel@nongnu.org; Mon, 06 Jan 2020 09:30:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578321017; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=W+1ExaiqAqfQEXrhdhHvUzGCY2SKObqsetW6umjBdkI=; b=HfK7OGuvkFpfzxV5aZstMFlfQwsQsdPlI8orIbBQid/mWsRdbM7Wy4vfjva4TGQ+bvjYX8 Av0Rl07wjzzf3o0YGzfXosyv9uUn1m1Dbq9ihje57Kb2WdPiAZNHovRkqGckcBzL31ZUi8 pMHUOizmyYDRGhFYX/HsnLOHVpnwY0g= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-322-vWZuVs-kM9GfFjdAqFui8g-1; Mon, 06 Jan 2020 09:30:15 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 081D41800D4E for ; Mon, 6 Jan 2020 14:30:15 +0000 (UTC) Received: from redhat.com (unknown [10.42.16.105]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A2A2D858A2; Mon, 6 Jan 2020 14:30:11 +0000 (UTC) Date: Mon, 6 Jan 2020 14:30:11 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Dr. David Alan Gilbert (git)" Subject: Re: [PATCH 032/104] virtiofsd: passthrough_ll: create new files in caller's context Message-ID: <20200106143011.GK2930416@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> <20191212163904.159893-33-dgilbert@redhat.com> MIME-Version: 1.0 In-Reply-To: <20191212163904.159893-33-dgilbert@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: vWZuVs-kM9GfFjdAqFui8g-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Dec 12, 2019 at 04:37:52PM +0000, Dr. David Alan Gilbert (git) wrot= e: > From: Vivek Goyal >=20 > We need to create files in the caller's context. Otherwise after > creating a file, the caller might not be able to do file operations on > that file. >=20 > Changed effective uid/gid to caller's uid/gid, create file and then > switch back to uid/gid 0. >=20 > Use syscall(setresuid, ...) otherwise glibc does some magic to change EUI= D > in all threads, which is not what we want. >=20 > Signed-off-by: Vivek Goyal > Signed-off-by: Miklos Szeredi > --- > tools/virtiofsd/passthrough_ll.c | 79 ++++++++++++++++++++++++++++++-- > 1 file changed, 74 insertions(+), 5 deletions(-) >=20 > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrou= gh_ll.c > index 68bacb6fc5..0188cd9ad6 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > +static int lo_change_cred(fuse_req_t req, struct lo_cred *old) > +{ > + int res; > + > + old->euid =3D geteuid(); > + old->egid =3D getegid(); > + > + res =3D syscall(SYS_setresgid, -1, fuse_req_ctx(req)->gid, -1); Do we need to be using SYS_setres[u,g]id32 instead... [quote setresgid(2)] The original Linux setresuid() and setresgid() system calls supported only 16-bit user and group IDs. Subsequently, Linux 2.4 added setresuid32() and setresgid32(), supporting 32-bit IDs. The glibc setresuid() and setresgid() wrapper functions transparently deal with the variations across ker=E2=80=90 nel versions. [/quote] > + if (res =3D=3D -1) { > + return errno; > + } > + > + res =3D syscall(SYS_setresuid, -1, fuse_req_ctx(req)->uid, -1); > + if (res =3D=3D -1) { > + int errno_save =3D errno; > + > + syscall(SYS_setresgid, -1, old->egid, -1); > + return errno_save; > + } > + > + return 0; > +} > + > +/* Regain Privileges */ > +static void lo_restore_cred(struct lo_cred *old) > +{ > + int res; > + > + res =3D syscall(SYS_setresuid, -1, old->euid, -1); > + if (res =3D=3D -1) { > + fuse_log(FUSE_LOG_ERR, "seteuid(%u): %m\n", old->euid); > + exit(1); > + } > + > + res =3D syscall(SYS_setresgid, -1, old->egid, -1); > + if (res =3D=3D -1) { > + fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid); > + exit(1); > + } > +} > + > static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, > const char *name, mode_t mode, dev_t rdev, > const char *link) > @@ -391,12 +443,21 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_i= no_t parent, > int saverr; > struct lo_inode *dir =3D lo_inode(req, parent); > struct fuse_entry_param e; > + struct lo_cred old =3D {}; > =20 > saverr =3D ENOMEM; > =20 > + saverr =3D lo_change_cred(req, &old); > + if (saverr) { > + goto out; > + } > + > res =3D mknod_wrapper(dir->fd, name, link, mode, rdev); > =20 > saverr =3D errno; > + > + lo_restore_cred(&old); > + > if (res =3D=3D -1) { > goto out; > } > @@ -794,26 +855,34 @@ static void lo_create(fuse_req_t req, fuse_ino_t pa= rent, const char *name, > struct lo_data *lo =3D lo_data(req); > struct fuse_entry_param e; > int err; > + struct lo_cred old =3D {}; > =20 > if (lo_debug(req)) { > fuse_log(FUSE_LOG_DEBUG, "lo_create(parent=3D%" PRIu64 ", name= =3D%s)\n", > parent, name); > } > =20 > + err =3D lo_change_cred(req, &old); > + if (err) { > + goto out; > + } > + > fd =3D openat(lo_fd(req, parent), name, (fi->flags | O_CREAT) & ~O_N= OFOLLOW, > mode); > - if (fd =3D=3D -1) { > - return (void)fuse_reply_err(req, errno); > - } > + err =3D fd =3D=3D -1 ? errno : 0; > + lo_restore_cred(&old); > =20 > - fi->fh =3D fd; > + if (!err) { > + fi->fh =3D fd; > + err =3D lo_do_lookup(req, parent, name, &e); > + } > if (lo->cache =3D=3D CACHE_NEVER) { > fi->direct_io =3D 1; > } else if (lo->cache =3D=3D CACHE_ALWAYS) { > fi->keep_cache =3D 1; > } > =20 > - err =3D lo_do_lookup(req, parent, name, &e); > +out: > if (err) { > fuse_reply_err(req, err); > } else { > --=20 > 2.23.0 >=20 >=20 Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|