From nobody Fri Oct 3 11:32:56 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1579808306; cv=none; d=zohomail.com; s=zohoarc; b=J1cZ9sluPRpAsd0pUC9lKB8CH6XpGeIsFL1nDqRjkNAdEsuL8tWt9inKuq+xSI2ThqkV2QdX3ptvU0t5qYIj776jE4CstpHIKvBk9jeQSm/j8a/UCu47IeImmQC6JH6MRmesHe86UtFqaTP0pg4E0Z4u3Yw+aJtuUOThRX6N15Y= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1579808306; h=Content-Type:Content-Transfer-Encoding:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=pRi6vYFNhs/j1llGXVOGVhSwK/ObAljmvQ/qv9tM0tY=; b=mN3x5dP8aLvMYXtO4nwO4KW44YCj7yYhGeXnT5Tros/aVxQPaMw0yR6rBEeq8YRC8CeZzzzCcmXapr68L6DaJ8RA0DO5i0bCX1A2Y2UvVBWRXjyQ9BmuDWp8631hzdlEHR2OrYD5zHr3lRFcgJR35N5JHIEJO/lyyjlFw2qDdnQ= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 15798083063121001.0094515131556; Thu, 23 Jan 2020 11:38:26 -0800 (PST) Received: from localhost ([::1]:60270 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iuiJ7-00011L-4b for importer@patchew.org; Thu, 23 Jan 2020 14:38:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41186) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iufdl-0004lc-2m for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iufdj-0006Rt-QJ for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:33 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:33705 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 1iufdj-0006Rl-No for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:31 -0500 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-23-K0JJm_mFNjiBGk8LgEePBg-1; Thu, 23 Jan 2020 11:47:30 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 13309107ACC4 for ; Thu, 23 Jan 2020 16:47:29 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-110.ams2.redhat.com [10.36.116.110]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5EB3A19C69; Thu, 23 Jan 2020 16:47:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579798051; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pRi6vYFNhs/j1llGXVOGVhSwK/ObAljmvQ/qv9tM0tY=; b=JSdybYzLKUn81jsl9DNBhNgjfQU/y4A8jhael0Y5oJ9WtJsuwkvAho4LBs/B2MBSb5vuzS Cd919+s9TRtxCNHySfW4+kukQF+WBg53ZrljjWopnXFpvLSunFWPs42s8sIcTvhDxpgjy9 Sz4JE1A6OWwxrOF/ezpSeExj8cGEczQ= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com Subject: [PULL 034/108] virtiofsd: passthrough_ll: create new files in caller's context Date: Thu, 23 Jan 2020 16:45:16 +0000 Message-Id: <20200123164630.91498-35-dgilbert@redhat.com> In-Reply-To: <20200123164630.91498-1-dgilbert@redhat.com> References: <20200123164630.91498-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: K0JJm_mFNjiBGk8LgEePBg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 207.211.31.81 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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: Vivek Goyal 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. Changed effective uid/gid to caller's uid/gid, create file and then switch back to uid/gid 0. Use syscall(setresuid, ...) otherwise glibc does some magic to change EUID in all threads, which is not what we want. Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 96 ++++++++++++++++++++++++++++++-- 1 file changed, 91 insertions(+), 5 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index cd27c09f59..5e061797d4 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -50,6 +50,7 @@ #include #include #include +#include #include #include =20 @@ -83,6 +84,11 @@ struct lo_inode { uint64_t refcount; /* protected by lo->mutex */ }; =20 +struct lo_cred { + uid_t euid; + gid_t egid; +}; + enum { CACHE_NEVER, CACHE_NORMAL, @@ -383,6 +389,69 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t paren= t, const char *name) } } =20 +/* + * On some archs, setres*id is limited to 2^16 but they + * provide setres*id32 variants that allow 2^32. + * Others just let setres*id do 2^32 anyway. + */ +#ifdef SYS_setresgid32 +#define OURSYS_setresgid SYS_setresgid32 +#else +#define OURSYS_setresgid SYS_setresgid +#endif + +#ifdef SYS_setresuid32 +#define OURSYS_setresuid SYS_setresuid32 +#else +#define OURSYS_setresuid SYS_setresuid +#endif + +/* + * Change to uid/gid of caller so that file is created with + * ownership of caller. + * TODO: What about selinux context? + */ +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(OURSYS_setresgid, -1, fuse_req_ctx(req)->gid, -1); + if (res =3D=3D -1) { + return errno; + } + + res =3D syscall(OURSYS_setresuid, -1, fuse_req_ctx(req)->uid, -1); + if (res =3D=3D -1) { + int errno_save =3D errno; + + syscall(OURSYS_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(OURSYS_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(OURSYS_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 +460,21 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino= _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 +872,34 @@ static void lo_create(fuse_req_t req, fuse_ino_t pare= nt, 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_NOF= OLLOW, 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 2.24.1