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[82.29.237.198]) by smtp.gmail.com with ESMTPSA id c7sm15552340wrs.23.2021.06.28.11.51.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Jun 2021 11:51:37 -0700 (PDT) Date: Mon, 28 Jun 2021 19:51:36 +0100 From: "Dr. David Alan Gilbert" To: Vivek Goyal Subject: Re: [PATCH v7 5/7] virtiofsd: Add capability to change/restore umask Message-ID: References: <20210622150852.1507204-1-vgoyal@redhat.com> <20210622150852.1507204-6-vgoyal@redhat.com> <20210628181218.GF1803896@redhat.com> <20210628184636.GH1803896@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210628184636.GH1803896@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.375, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Cc: virtio-fs@redhat.com, miklos@szeredi.hu, qemu-devel@nongnu.org, lhenriques@suse.de Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Vivek Goyal (vgoyal@redhat.com) wrote: > On Mon, Jun 28, 2021 at 07:36:18PM +0100, Dr. David Alan Gilbert wrote: > > * Vivek Goyal (vgoyal@redhat.com) wrote: > > > On Mon, Jun 28, 2021 at 05:12:13PM +0100, Dr. David Alan Gilbert wrote: > > > > * Vivek Goyal (vgoyal@redhat.com) wrote: > > > > > When parent directory has default acl and a file is created in that > > > > > directory, then umask is ignored and final file permissions are > > > > > determined using default acl instead. (man 2 umask). > > > > > > > > > > Currently, fuse applies the umask and sends modified mode in create > > > > > request accordingly. fuse server can set FUSE_DONT_MASK and tell > > > > > fuse client to not apply umask and fuse server will take care of > > > > > it as needed. > > > > > > > > > > With posix acls enabled, requirement will be that we want umask > > > > > to determine final file mode if parent directory does not have > > > > > default acl. > > > > > > > > > > So if posix acls are enabled, opt in for FUSE_DONT_MASK. virtiofsd > > > > > will set umask of the thread doing file creation. And host kernel > > > > > should use that umask if parent directory does not have default > > > > > acls, otherwise umask does not take affect. > > > > > > > > > > Miklos mentioned that we already call unshare(CLONE_FS) for > > > > > every thread. That means umask has now become property of per > > > > > thread and it should be ok to manipulate it in file creation path. > > > > > > > > > > This patch only adds capability to change umask and restore it. It > > > > > does not enable it yet. Next few patches will add capability to enable it > > > > > based on if user enabled posix_acl or not. > > > > > > > > > > This should fix fstest generic/099. > > > > > > > > > > Reported-by: Luis Henriques > > > > > Signed-off-by: Vivek Goyal > > > > > Reviewed-by: Stefan Hajnoczi > > > > > --- > > > > > tools/virtiofsd/passthrough_ll.c | 22 ++++++++++++++++------ > > > > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > > > > > > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > > > > > index 9f5cd98fb5..0c9084ea15 100644 > > > > > --- a/tools/virtiofsd/passthrough_ll.c > > > > > +++ b/tools/virtiofsd/passthrough_ll.c > > > > > @@ -122,6 +122,7 @@ struct lo_inode { > > > > > struct lo_cred { > > > > > uid_t euid; > > > > > gid_t egid; > > > > > + mode_t umask; > > > > > }; > > > > > > > > > > enum { > > > > > @@ -172,6 +173,8 @@ struct lo_data { > > > > > /* An O_PATH file descriptor to /proc/self/fd/ */ > > > > > int proc_self_fd; > > > > > int user_killpriv_v2, killpriv_v2; > > > > > + /* If set, virtiofsd is responsible for setting umask during creation */ > > > > > + bool change_umask; > > > > > }; > > > > > > > > > > static const struct fuse_opt lo_opts[] = { > > > > > @@ -1134,7 +1137,8 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) > > > > > * ownership of caller. > > > > > * TODO: What about selinux context? > > > > > */ > > > > > -static int lo_change_cred(fuse_req_t req, struct lo_cred *old) > > > > > +static int lo_change_cred(fuse_req_t req, struct lo_cred *old, > > > > > + bool change_umask) > > > > > { > > > > > int res; > > > > > > > > > > @@ -1154,11 +1158,14 @@ static int lo_change_cred(fuse_req_t req, struct lo_cred *old) > > > > > return errno_save; > > > > > } > > > > > > > > > > + if (change_umask) { > > > > > + old->umask = umask(req->ctx.umask); > > > > > + } > > > > > return 0; > > > > > } > > > > > > > > > > /* Regain Privileges */ > > > > > -static void lo_restore_cred(struct lo_cred *old) > > > > > +static void lo_restore_cred(struct lo_cred *old, bool restore_umask) > > > > > { > > > > > int res; > > > > > > > > > > @@ -1173,6 +1180,9 @@ static void lo_restore_cred(struct lo_cred *old) > > > > > fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid); > > > > > exit(1); > > > > > } > > > > > + > > > > > + if (restore_umask) > > > > > + umask(old->umask); > > > > > } > > > > > > > > > > static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, > > > > > @@ -1202,7 +1212,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, > > > > > return; > > > > > } > > > > > > > > > > - saverr = lo_change_cred(req, &old); > > > > > + saverr = lo_change_cred(req, &old, lo->change_umask && !S_ISLNK(mode)); > > > > > > > > Can you explain what these ISLNK checks are for (insid mknod_symlink, so > > > > is that always true or irrelevant?) > > > > > > I think I put this check in because if we are creating symlink then we > > > don't have to change umask as symlink will always get a some fix > > > mode (usually 777) and umask will not have an affect. So this is > > > just an optimization to avoid switching umask in some cases. I > > > can't think of any other reason. > > > > But this is in 'lo_mknod_symlink' - so when do we call that except for > > making symlinks? > > I think it is called for other mknod paths as well and not limited to > symlink only. > > > static void lo_mknod(fuse_req_t req, fuse_ino_t parent, const char *name, > mode_t mode, dev_t rdev) > { > lo_mknod_symlink(req, parent, name, mode, rdev, NULL); > } > > static void lo_mkdir(fuse_req_t req, fuse_ino_t parent, const char *name, > mode_t mode) > { > lo_mknod_symlink(req, parent, name, S_IFDIR | mode, 0, NULL); > } > > static void lo_symlink(fuse_req_t req, const char *link, fuse_ino_t parent, > const char *name) > { > lo_mknod_symlink(req, parent, name, S_IFLNK, 0, link); > } Oh, I see, yeh that confused me - it all then goes through mknod_wrapper. Right, Reviewed-by: Dr. David Alan Gilbert > Vivek > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK