From f62613d8058bcb60b26727d980a37537103b0033 Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Mon, 27 Jan 2020 19:01:32 +0100 Subject: [PATCH 061/116] virtiofsd: cap-ng helpers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Dr. David Alan Gilbert Message-id: <20200127190227.40942-58-dgilbert@redhat.com> Patchwork-id: 93512 O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 057/112] virtiofsd: cap-ng helpers Bugzilla: 1694164 RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Sergio Lopez Pascual From: "Dr. David Alan Gilbert" libcap-ng reads /proc during capng_get_caps_process, and virtiofsd's sandboxing doesn't have /proc mounted; thus we have to do the caps read before we sandbox it and save/restore the state. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Daniel P. Berrangé Signed-off-by: Dr. David Alan Gilbert (cherry picked from commit 2405f3c0d19eb4d516a88aa4e5c54e5f9c6bbea3) Signed-off-by: Miroslav Rezanina --- Makefile | 4 +-- tools/virtiofsd/passthrough_ll.c | 72 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 74 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index 6879a06..ff05c30 100644 --- a/Makefile +++ b/Makefile @@ -330,7 +330,7 @@ endif endif endif -ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy) +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy) HELPERS-y += virtiofsd$(EXESUF) vhost-user-json-y += tools/virtiofsd/50-qemu-virtiofsd.json endif @@ -682,7 +682,7 @@ rdmacm-mux$(EXESUF): $(rdmacm-mux-obj-y) $(COMMON_LDADDS) $(call LINK, $^) # relies on Linux-specific syscalls -ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy) +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy) virtiofsd$(EXESUF): $(virtiofsd-obj-y) libvhost-user.a $(COMMON_LDADDS) $(call LINK, $^) endif diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index bd8925b..97e7c75 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -39,6 +39,7 @@ #include "fuse_virtio.h" #include "fuse_lowlevel.h" #include +#include #include #include #include @@ -139,6 +140,13 @@ static const struct fuse_opt lo_opts[] = { static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n); +static struct { + pthread_mutex_t mutex; + void *saved; +} cap; +/* That we loaded cap-ng in the current thread from the saved */ +static __thread bool cap_loaded = 0; + static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st); static int is_dot_or_dotdot(const char *name) @@ -162,6 +170,37 @@ static struct lo_data *lo_data(fuse_req_t req) return (struct lo_data *)fuse_req_userdata(req); } +/* + * Load capng's state from our saved state if the current thread + * hadn't previously been loaded. + * returns 0 on success + */ +static int load_capng(void) +{ + if (!cap_loaded) { + pthread_mutex_lock(&cap.mutex); + capng_restore_state(&cap.saved); + /* + * restore_state free's the saved copy + * so make another. + */ + cap.saved = capng_save_state(); + if (!cap.saved) { + fuse_log(FUSE_LOG_ERR, "capng_save_state (thread)\n"); + return -EINVAL; + } + pthread_mutex_unlock(&cap.mutex); + + /* + * We want to use the loaded state for our pid, + * not the original + */ + capng_setpid(syscall(SYS_gettid)); + cap_loaded = true; + } + return 0; +} + static void lo_map_init(struct lo_map *map) { map->elems = NULL; @@ -2024,6 +2063,35 @@ static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) } /* + * Capture the capability state, we'll need to restore this for individual + * threads later; see load_capng. + */ +static void setup_capng(void) +{ + /* Note this accesses /proc so has to happen before the sandbox */ + if (capng_get_caps_process()) { + fuse_log(FUSE_LOG_ERR, "capng_get_caps_process\n"); + exit(1); + } + pthread_mutex_init(&cap.mutex, NULL); + pthread_mutex_lock(&cap.mutex); + cap.saved = capng_save_state(); + if (!cap.saved) { + fuse_log(FUSE_LOG_ERR, "capng_save_state\n"); + exit(1); + } + pthread_mutex_unlock(&cap.mutex); +} + +static void cleanup_capng(void) +{ + free(cap.saved); + cap.saved = NULL; + pthread_mutex_destroy(&cap.mutex); +} + + +/* * Make the source directory our root so symlinks cannot escape and no other * files are accessible. Assumes unshare(CLONE_NEWNS) was already called. */ @@ -2216,12 +2284,16 @@ int main(int argc, char *argv[]) fuse_daemonize(opts.foreground); + /* Must be before sandbox since it wants /proc */ + setup_capng(); + setup_sandbox(&lo, se); /* Block until ctrl+c or fusermount -u */ ret = virtio_loop(se); fuse_session_unmount(se); + cleanup_capng(); err_out3: fuse_remove_signal_handlers(se); err_out2: -- 1.8.3.1