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Thu, 24 Oct 2019 11:27:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571916455; 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=4FPgYQFbJ3wa5Enj07AEd7Fjkhsti21C0RndqxjWCWY=; b=VQDHu1Y969YbchyvyxlB7wz7ksDIH1spQ1hPTT5s3EbRIhOX0c+g+GjrOHizYqjcPupuNI ybKNQiDQNQdGuoZf5zL10HuryfQ8ak6BDadakIdGhjezD2vcUK9IW/1/n0mxOUVDVHwf2U 3vEWXUJtJJCdLAX2mnXa1n5j2YObV/0= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, renzhen@linux.alibaba.com, eguan@linux.alibaba.com, ganesh.mahalingam@intel.com, m.mizuma@jp.fujitsu.com, mszeredi@redhat.com, misono.tomohiro@jp.fujitsu.com, tao.peng@linux.alibaba.com, piaojun@huawei.com, stefanha@redhat.com, vgoyal@redhat.com, mst@redhat.com, berrange@redhat.com Subject: [PATCH 01/25] virtiofsd: passthrough_ll: create new files in caller's context Date: Thu, 24 Oct 2019 12:26:54 +0100 Message-Id: <20191024112718.34657-2-dgilbert@redhat.com> In-Reply-To: <20191024112718.34657-1-dgilbert@redhat.com> References: <20191024112718.34657-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: Yg2AnGDPMAGt8oGVVt1gXA-1 X-Mimecast-Spam-Score: 0 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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 callers context. Otherwise afer creating file, caller himself 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 backto 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 --- contrib/virtiofsd/passthrough_ll.c | 75 ++++++++++++++++++++++++++++-- 1 file changed, 71 insertions(+), 4 deletions(-) diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthr= ough_ll.c index 2a1a880224..2de35d4d3d 100644 --- a/contrib/virtiofsd/passthrough_ll.c +++ b/contrib/virtiofsd/passthrough_ll.c @@ -49,6 +49,7 @@ #include #include #include +#include #include =20 #include "passthrough_helpers.h" @@ -78,6 +79,11 @@ 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, @@ -376,6 +382,51 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t paren= t, const char *name) fuse_reply_entry(req, &e); } =20 +/* + * 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(SYS_setresgid, -1,fuse_req_ctx(req)->gid, -1); + 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) @@ -384,12 +435,20 @@ 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; =20 @@ -768,23 +827,31 @@ 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_NOFOLLOW, 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