From: Bernd Schubert Signed-off-by: Bernd Schubert --- util/fusermount.c | 302 +++++++++++++++++++++++++++++++++++++++++++++++++++--- util/meson.build | 2 +- 2 files changed, 291 insertions(+), 13 deletions(-) diff --git a/util/fusermount.c b/util/fusermount.c index d42e16955f6d26f81e6d2a5acb040b1448e20b51..31bf959024ae0cd2a4e50974589bfab30a100b0a 100644 --- a/util/fusermount.c +++ b/util/fusermount.c @@ -11,6 +11,9 @@ #include "fuse_config.h" #include "mount_util.h" #include "util.h" +#if __linux__ +#include "mount_i_linux.h" +#endif #include #include @@ -923,6 +926,7 @@ static void free_mount_params(struct mount_params *mp) free(mp->source); free(mp->type); free(mp->mnt_opts); + memset(mp, 0, sizeof(*mp)); } /* @@ -1309,6 +1313,171 @@ static int open_fuse_device(const char *dev) return fd; } +/* + * Context for split mount operation (sync-init mode) + */ +struct mount_context { + int fd; + const char *dev; + struct stat stbuf; + char *source; + char *mnt_opts; + char *x_opts; + const char *type; +}; + +/* + * Phase 1: Open device and prepare for mount (sync-init mode) + * Returns fd on success, -1 on failure + */ +static int mount_fuse_prepare(const char *mnt, const char *opts, + struct mount_context *ctx) +{ + int res; + int mountpoint_fd = -1; + char *do_mount_opts = NULL; + const char *real_mnt = mnt; + + memset(ctx, 0, sizeof(*ctx)); + ctx->dev = getenv(FUSE_KERN_DEVICE_ENV) ?: FUSE_DEV; + + ctx->fd = open_fuse_device(ctx->dev); + if (ctx->fd == -1) + return -1; + + drop_privs(); + read_conf(); + + if (getuid() != 0 && mount_max != -1) { + int mount_count = count_fuse_fs(); + + if (mount_count >= mount_max) { + fprintf(stderr, + "%s: too many FUSE filesystems mounted; mount_max=N can be set in %s\n", + progname, FUSE_CONF); + goto fail_close_fd; + } + } + + res = extract_x_options(opts, &do_mount_opts, &ctx->x_opts); + if (res) + goto fail_close_fd; + + res = check_perm(&real_mnt, &ctx->stbuf, &mountpoint_fd); + restore_privs(); + + if (mountpoint_fd != -1) + close(mountpoint_fd); + + if (res == -1) + goto fail_close_fd; + + free(do_mount_opts); + return ctx->fd; + +fail_close_fd: + close(ctx->fd); + free(do_mount_opts); + free(ctx->x_opts); + ctx->fd = -1; + return -1; +} + +#ifdef HAVE_NEW_MOUNT_API +/* + * Phase 2: Perform the actual mount using new mount API (sync-init mode) + * Returns 0 on success, -1 on failure + */ +static int mount_fuse_finish_fsmount(const char *mnt, const char *opts, + struct mount_context *ctx, + const char **type) +{ + int res; + char *do_mount_opts = NULL; + char *x_prefixed_opts = NULL; + struct mount_params mp = { + .fd = ctx->fd, + .rootmode = ctx->stbuf.st_mode & S_IFMT, + .dev = ctx->dev, + }; + char *final_mnt_opts = NULL; + + /* Extract x-options */ + res = extract_x_options(opts, &do_mount_opts, &x_prefixed_opts); + if (res) + goto fail; + + res = prepare_mount(do_mount_opts, &mp); + if (res == -1) + goto fail; + + /* Merge x-options if running as root */ + final_mnt_opts = mp.mnt_opts; + if (geteuid() == 0 && ctx->x_opts && strlen(ctx->x_opts) > 0) { + size_t mnt_opts_len = strlen(mp.mnt_opts); + size_t x_mnt_opts_len = mnt_opts_len + strlen(ctx->x_opts) + 2; + char *x_mnt_opts = calloc(1, x_mnt_opts_len); + + if (!x_mnt_opts) + goto fail_free_params; + + if (mnt_opts_len) { + strcpy(x_mnt_opts, mp.mnt_opts); + strncat(x_mnt_opts, ",", 2); + } + strncat(x_mnt_opts, ctx->x_opts, + x_mnt_opts_len - mnt_opts_len - 2); + + final_mnt_opts = x_mnt_opts; + } + + /* Use new mount API */ + res = fuse_kern_fsmount(mnt, mp.flags, mp.blkdev, + mp.fsname, mp.subtype, ctx->dev, + mp.optbuf, final_mnt_opts); + if (res == -1) + goto fail_free_merged; + + /* Change to root directory */ + res = chdir("/"); + if (res == -1) { + fprintf(stderr, "%s: failed to chdir to '/'\n", progname); + goto fail_free_merged; + } + + /* Store results in context */ + ctx->source = mp.source; + ctx->type = mp.type; + ctx->mnt_opts = final_mnt_opts; + *type = mp.type; + + res = 0; + + /* Only free what is not assigned to ctx */ + free(mp.fsname); + free(mp.subtype); + free(mp.optbuf); + if (final_mnt_opts != mp.mnt_opts) + free(mp.mnt_opts); + +out: + free(do_mount_opts); + free(x_prefixed_opts); + + return res; + +fail_free_merged: + if (final_mnt_opts != mp.mnt_opts) + free(final_mnt_opts); +fail_free_params: + free_mount_params(&mp); +fail: + res = -1; + goto out; +} +#endif /* HAVE_NEW_MOUNT_API */ + + static int mount_fuse(const char *mnt, const char *opts, const char **type) { int res; @@ -1404,6 +1573,65 @@ fail_close_fd: goto out_free; } +/* Forward declarations for helper functions */ +static int send_fd(int sock_fd, int fd); +static int wait_for_signal(int sock_fd); + +#ifdef HAVE_NEW_MOUNT_API +/* + * Perform sync-init mount using new mount API + * Returns 0 on success, -1 on failure + */ +static int mount_fuse_sync_init(const char *mnt, const char *opts, + int cfd, const char **type) +{ + struct mount_context ctx; + int fd, res; + int32_t status, send_res; + + /* Phase 1: Open device and prepare */ + fd = mount_fuse_prepare(mnt, opts, &ctx); + if (fd == -1) + return -1; + + /* Send fd to caller so it can start worker thread */ + res = send_fd(cfd, fd); + if (res != 0) { + close(fd); + free(ctx.x_opts); + return -1; + } + + /* Wait for caller to signal that worker thread is ready */ + res = wait_for_signal(cfd); + if (res != 0) { + close(fd); + free(ctx.x_opts); + return -1; + } + + /* Phase 2: Perform the actual mount using new API */ + res = mount_fuse_finish_fsmount(mnt, opts, &ctx, type); + + /* Send mount result back to caller (4-byte error code) */ + status = (res == 0) ? 0 : -(int32_t)errno; + do { + send_res = send(cfd, &status, sizeof(status), 0); + } while (send_res == -1 && errno == EINTR); + if (send_res != sizeof(status)) { + fprintf(stderr, "%s: failed to send mount status: %s\n", + progname, strerror(errno)); + } + + close(fd); + free(ctx.source); + free(ctx.mnt_opts); + free(ctx.x_opts); + + return res; +} +#endif /* HAVE_NEW_MOUNT_API */ + static int send_fd(int sock_fd, int fd) { int retval; @@ -1440,6 +1668,30 @@ static int send_fd(int sock_fd, int fd) return 0; } +/* + * Wait for a signal byte from the caller. + * Returns 0 on success, -1 on error. + */ +static int wait_for_signal(int sock_fd) +{ + char buf[1]; + int res; + + do { + res = recv(sock_fd, buf, sizeof(buf), 0); + } while (res == -1 && errno == EINTR); + if (res != 1) { + if (res == 0) + fprintf(stderr, "%s: connection closed while waiting for signal\n", + progname); + else + fprintf(stderr, "%s: error receiving signal: %s\n", + progname, strerror(errno)); + return -1; + } + return 0; +} + /* Helper for should_auto_unmount * * fusermount typically has the s-bit set - initial open of `mnt` was as root @@ -1631,6 +1883,7 @@ int main(int argc, char *argv[]) const char *opts = ""; const char *type = NULL; int setup_auto_unmount_only = 0; + int sync_init_mode = 0; static const struct option long_opts[] = { {"unmount", no_argument, NULL, 'u'}, @@ -1643,6 +1896,7 @@ int main(int argc, char *argv[]) // They'ne meant for internal use by mount.c {"auto-unmount", no_argument, NULL, 'U'}, {"comm-fd", required_argument, NULL, 'c'}, + {"sync-init", no_argument, NULL, 'S'}, {0, 0, 0, 0}}; progname = strdup(argc > 0 ? argv[0] : "fusermount"); @@ -1677,6 +1931,9 @@ int main(int argc, char *argv[]) case 'c': commfd = optarg; break; + case 'S': + sync_init_mode = 1; + break; case 'z': lazy = 1; break; @@ -1754,21 +2011,42 @@ int main(int argc, char *argv[]) if (setup_auto_unmount_only) goto wait_for_auto_unmount; - fd = mount_fuse(mnt, opts, &type); - if (fd == -1) - goto err_out; + if (sync_init_mode) { +#ifdef HAVE_NEW_MOUNT_API + res = mount_fuse_sync_init(mnt, opts, cfd, &type); + if (res == -1) + goto err_out; - res = send_fd(cfd, fd); - if (res != 0) { - umount2(mnt, MNT_DETACH); /* lazy umount */ + if (!auto_unmount) { + free(mnt); + free((void *) type); + return 0; + } + /* Continue to auto_unmount handling below */ +#else + fprintf(stderr, "%s: sync-init mode requires new mount API support\n", + progname); + fprintf(stderr, "%s: kernel or headers too old (need fsopen/fsmount)\n", + progname); goto err_out; - } - close(fd); +#endif + } else { + fd = mount_fuse(mnt, opts, &type); + if (fd == -1) + goto err_out; - if (!auto_unmount) { - free(mnt); - free((void*) type); - return 0; + res = send_fd(cfd, fd); + if (res != 0) { + umount2(mnt, MNT_DETACH); /* lazy umount */ + goto err_out; + } + close(fd); + + if (!auto_unmount) { + free(mnt); + free((void *) type); + return 0; + } } wait_for_auto_unmount: diff --git a/util/meson.build b/util/meson.build index 0e4b1cce95377e73af7dc45655a7088315497ddb..731ef95488461ac21c21b1972a96d58b1187dc5a 100644 --- a/util/meson.build +++ b/util/meson.build @@ -1,6 +1,6 @@ fuseconf_path = join_paths(get_option('prefix'), get_option('sysconfdir'), 'fuse.conf') -executable('fusermount3', ['fusermount.c', '../lib/mount_util.c', '../lib/util.c'], +executable('fusermount3', ['fusermount.c', '../lib/mount_util.c', '../lib/mount_fsmount.c', '../lib/util.c'], include_directories: include_dirs, install: true, install_dir: get_option('bindir'), -- 2.43.0