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Thu, 25 Jun 2020 16:29:41 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-114-254.ams2.redhat.com [10.36.114.254]) by smtp.corp.redhat.com (Postfix) with ESMTP id E9E0CA09BF; Thu, 25 Jun 2020 16:29:40 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, virtio-fs@redhat.com, stefanha@redhat.com, vgoyal@redhat.com Subject: [PATCH 3/3] virtiofsd: Allow addition or removal of capabilities Date: Thu, 25 Jun 2020 17:29:29 +0100 Message-Id: <20200625162929.46672-4-dgilbert@redhat.com> In-Reply-To: <20200625162929.46672-1-dgilbert@redhat.com> References: <20200625162929.46672-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=207.211.31.120; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/25 01:47:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: "Dr. David Alan Gilbert" Allow capabilities to be added or removed from the allowed set for the daemon; e.g. default: CapPrm: 00000000880000df CapEff: 00000000880000df -o modcaps=+sys_admin CapPrm: 00000000882000df CapEff: 00000000882000df -o modcaps=+sys_admin:-chown CapPrm: 00000000882000de CapEff: 00000000882000de Signed-off-by: Dr. David Alan Gilbert --- docs/tools/virtiofsd.rst | 5 ++++ tools/virtiofsd/helper.c | 2 ++ tools/virtiofsd/passthrough_ll.c | 50 ++++++++++++++++++++++++++++++-- 3 files changed, 55 insertions(+), 2 deletions(-) diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst index 378594c422..824e713491 100644 --- a/docs/tools/virtiofsd.rst +++ b/docs/tools/virtiofsd.rst @@ -54,6 +54,11 @@ Options * flock|no_flock - Enable/disable flock. The default is ``no_flock``. + * modcaps=CAPLIST + Modify the list of capabilities allowed; CAPLIST is a colon separated + list of capabilities, each preceded by either + or -, e.g. + ''+sys_admin:-chown''. + * log_level=LEVEL - Print only log messages matching LEVEL or more severe. LEVEL is one of ``err``, ``warn``, ``info``, or ``debug``. The default is ``info``. diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c index 00a1ef666a..3105b6c23a 100644 --- a/tools/virtiofsd/helper.c +++ b/tools/virtiofsd/helper.c @@ -174,6 +174,8 @@ void fuse_cmdline_help(void) " default: no_writeback\n" " -o xattr|no_xattr enable/disable xattr\n" " default: no_xattr\n" + " -o modcaps=CAPLIST Modify the list of capabilities\n" + " e.g. -o modcaps=+sys_admin:-chown\n" " --rlimit-nofile= set maximum number of file descriptors\n" " (0 leaves rlimit unchanged)\n" " default: min(1000000, fs.file-max - 16384)\n" diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 99d562046a..9d2cbc70ca 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -145,6 +145,7 @@ struct lo_data { int posix_lock; int xattr; char *source; + char *modcaps; double timeout; int cache; int timeout_set; @@ -170,6 +171,7 @@ static const struct fuse_opt lo_opts[] = { { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 }, { "xattr", offsetof(struct lo_data, xattr), 1 }, { "no_xattr", offsetof(struct lo_data, xattr), 0 }, + { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 }, { "timeout=%lf", offsetof(struct lo_data, timeout), 0 }, { "timeout=", offsetof(struct lo_data, timeout_set), 1 }, { "cache=none", offsetof(struct lo_data, cache), CACHE_NONE }, @@ -2571,7 +2573,7 @@ static void setup_mounts(const char *source) /* * Only keep whitelisted capabilities that are needed for file system operation */ -static void setup_capabilities(void) +static void setup_capabilities(struct lo_data *lo) { pthread_mutex_lock(&cap.mutex); capng_restore_state(&cap.saved); @@ -2604,6 +2606,50 @@ static void setup_capabilities(void) exit(1); } + /* + * The modcaps option is a colon separated list of caps, + * each preceded by either + or -. + */ + while (lo->modcaps) { + capng_act_t action; + int cap; + + char *next = strchr(lo->modcaps, ':'); + if (next) { + *next = '\0'; + next++; + } + + switch (lo->modcaps[0]) { + case '+': + action = CAPNG_ADD; + break; + + case '-': + action = CAPNG_DROP; + break; + + default: + fuse_log(FUSE_LOG_ERR, + "%s: Expecting '+'/'-' in modcaps but found '%c'\n", + __func__, lo->modcaps[0]); + exit(1); + } + cap = capng_name_to_capability(lo->modcaps + 1); + if (cap < 0) { + fuse_log(FUSE_LOG_ERR, "%s: Unknown capability '%s'\n", __func__, + lo->modcaps); + exit(1); + } + if (capng_update(action, CAPNG_PERMITTED | CAPNG_EFFECTIVE, cap)) { + fuse_log(FUSE_LOG_ERR, "%s: capng_update failed for '%s'\n", + __func__, lo->modcaps); + exit(1); + } + + lo->modcaps = next; + } + if (capng_apply(CAPNG_SELECT_BOTH)) { fuse_log(FUSE_LOG_ERR, "%s: capng_apply failed\n", __func__); exit(1); @@ -2627,7 +2673,7 @@ static void setup_sandbox(struct lo_data *lo, struct fuse_session *se, setup_namespaces(lo, se); setup_mounts(lo->source); setup_seccomp(enable_syslog); - setup_capabilities(); + setup_capabilities(lo); } /* Set the maximum number of open file descriptors */