| From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> |
| Date: Mon, 27 Jan 2020 19:01:32 +0000 |
| Subject: [PATCH] virtiofsd: cap-ng helpers |
| MIME-Version: 1.0 |
| Content-Type: text/plain; charset=UTF-8 |
| Content-Transfer-Encoding: 8bit |
| |
| 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 <dgilbert@redhat.com> |
| Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> |
| Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> |
| (cherry picked from commit 2405f3c0d19eb4d516a88aa4e5c54e5f9c6bbea3) |
| |
| Makefile | 4 +- |
| tools/virtiofsd/passthrough_ll.c | 72 ++++++++++++++++++++++++++++++++ |
| 2 files changed, 74 insertions(+), 2 deletions(-) |
| |
| diff --git a/Makefile b/Makefile |
| index 9a17e34603..14793cad11 100644 |
| |
| |
| @@ -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 |
| @@ -681,7 +681,7 @@ 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 bd8925bd83..97e7c75667 100644 |
| |
| |
| @@ -39,6 +39,7 @@ |
| #include "fuse_virtio.h" |
| #include "fuse_lowlevel.h" |
| #include <assert.h> |
| +#include <cap-ng.h> |
| #include <dirent.h> |
| #include <errno.h> |
| #include <inttypes.h> |
| @@ -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; |
| @@ -2023,6 +2062,35 @@ 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: |