Re: [libvirt] [PATCH] Make domain save work on root-squash NFS

Move *all* file operations related to creation and writing of libvirt header to the domain save file into a hook function that is called by virFileOperation. First try to call virFileOperation as root. If that fails with EACCESS, and (in the case of Linux) statfs says that we're trying to save the file on an NFS share, rerun virFileOperation, telling it to fork a child process and setuid to the qemu user. This is the only way we can successfully create a file on a root-squashed NFS server. This patch (along with setting dynamic_ownership=0 in qemu.conf) makes qemudDomainSave work on root-squashed NFS.

+#ifdef __linux__ + /* On Linux we can also verify the FS-type of the directory. */ + struct statfs st; + char *dirpath, *p;

+ + if ((p = strrchr(dirpath, '/')) == NULL) { + qemuReportError(VIR_ERR_INVALID_ARG, + _("Invalid path '%s' for domain save file"), + path); + VIR_FREE(dirpath); + goto endjob; + } + + if (p == dirpath) + *(p+1) = '\0'; + else + *p = '\0';

+ if (statfs(dirpath, &st) == -1) { + virReportSystemError(rc, + _("Failed to create domain save file '%s'" + " statfs of '%s' failed (%d)"), + path, errno); + VIR_FREE(dirpath); + goto endjob; + } + + VIR_FREE(dirpath); + + if (st.f_type != NFS_SUPER_MAGIC) { + virReportSystemError(rc, + _("Failed to create domain save file '%s' (fstype 0x%X"), + path, st.f_type); + goto endjob; + }

+#endif + + /* Retry creating the file as driver->user */ + + if ((rc = virFileOperation(path, O_CREAT|O_TRUNC|O_WRONLY, + S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP, + driver->user, driver->group, + qemudDomainSaveFileOpHook, &hdata, + VIR_FILE_OP_AS_UID)) != 0) { + virReportSystemError(rc, _("Error from child process creating '%s'"), + path); + goto endjob; + } + + /* Since we had to setuid to create the file, and the fstype + is NFS, we assume it's a root-squashing NFS share, and that + the security driver stuff would have failed anyway */ + + bypassSecurityDriver = 1; } - fd = -1; - if (driver->securityDriver && + + if ((!bypassSecurityDriver) && + driver->securityDriver && driver->securityDriver->domainSetSavedStateLabel && driver->securityDriver->domainSetSavedStateLabel(vm, path) == -1) goto endjob; @@ -4081,7 +4181,8 @@ static int qemudDomainSave(virDomainPtr dom, if (rc < 0) goto endjob; - if (driver->securityDriver && + if ((!bypassSecurityDriver) && + driver->securityDriver && driver->securityDriver->domainRestoreSavedStateLabel && driver->securityDriver->domainRestoreSavedStateLabel(vm, path) == -1) goto endjob; @@ -4106,8 +4207,6 @@ endjob: vm = NULL; cleanup: - if (fd != -1) - close(fd); VIR_FREE(xml); if (ret != 0) unlink(path);