From 9f59d175e2ca96f0b87f534dba69ea547dd35945 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 12 Mar 2019 15:48:50 +0000 Subject: [PATCH] virtiofsd: use /proc/self/fd/ O_PATH file descriptor MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sandboxing will remove /proc from the mount namespace so we can no longer build string paths into "/proc/self/fd/...". Keep an O_PATH file descriptor so we can still re-open fds via /proc/self/fd. Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 130 ++++++++++++++++++++++++------- 1 file changed, 103 insertions(+), 27 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index e3d65c3676..e2e2211ea1 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -110,6 +110,9 @@ struct lo_data { struct lo_map ino_map; /* protected by lo->mutex */ struct lo_map dirp_map; /* protected by lo->mutex */ struct lo_map fd_map; /* protected by lo->mutex */ + + /* An O_PATH file descriptor to /proc/self/fd/ */ + int proc_self_fd; }; static const struct fuse_opt lo_opts[] = { @@ -379,9 +382,9 @@ static int lo_parent_and_name(struct lo_data *lo, struct lo_inode *inode, int res; retry: - sprintf(procname, "/proc/self/fd/%i", inode->fd); + sprintf(procname, "%i", inode->fd); - res = readlink(procname, path, PATH_MAX); + res = readlinkat(lo->proc_self_fd, procname, path, PATH_MAX); if (res < 0) { fuse_log(FUSE_LOG_WARNING, "%s: readlink failed: %m\n", __func__); goto fail_noretry; @@ -477,9 +480,9 @@ static int utimensat_empty(struct lo_data *lo, struct lo_inode *inode, } return res; } - sprintf(path, "/proc/self/fd/%i", inode->fd); + sprintf(path, "%i", inode->fd); - return utimensat(AT_FDCWD, path, tv, 0); + return utimensat(lo->proc_self_fd, path, tv, 0); fallback: res = lo_parent_and_name(lo, inode, path, &parent); @@ -535,8 +538,8 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr, if (fi) { res = fchmod(fd, attr->st_mode); } else { - sprintf(procname, "/proc/self/fd/%i", ifd); - res = chmod(procname, attr->st_mode); + sprintf(procname, "%i", ifd); + res = fchmodat(lo->proc_self_fd, procname, attr->st_mode, 0); } if (res == -1) { goto out_err; @@ -552,11 +555,23 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr, } } if (valid & FUSE_SET_ATTR_SIZE) { + int truncfd; + if (fi) { - res = ftruncate(fd, attr->st_size); + truncfd = fd; } else { - sprintf(procname, "/proc/self/fd/%i", ifd); - res = truncate(procname, attr->st_size); + sprintf(procname, "%i", ifd); + truncfd = openat(lo->proc_self_fd, procname, O_RDWR); + if (truncfd < 0) { + goto out_err; + } + } + + res = ftruncate(truncfd, attr->st_size); + if (!fi) { + saverr = errno; + close(truncfd); + errno = saverr; } if (res == -1) { goto out_err; @@ -874,9 +889,9 @@ static int linkat_empty_nofollow(struct lo_data *lo, struct lo_inode *inode, return res; } - sprintf(path, "/proc/self/fd/%i", inode->fd); + sprintf(path, "%i", inode->fd); - return linkat(AT_FDCWD, path, dfd, name, AT_SYMLINK_FOLLOW); + return linkat(lo->proc_self_fd, path, dfd, name, AT_SYMLINK_FOLLOW); fallback: res = lo_parent_and_name(lo, inode, path, &parent); @@ -1404,8 +1419,8 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) fi->flags &= ~O_APPEND; } - sprintf(buf, "/proc/self/fd/%i", lo_fd(req, ino)); - fd = open(buf, fi->flags & ~O_NOFOLLOW); + sprintf(buf, "%i", lo_fd(req, ino)); + fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); if (fd == -1) { return (void)fuse_reply_err(req, errno); } @@ -1458,7 +1473,6 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync, struct fuse_file_info *fi) { int res; - (void)ino; int fd; char *buf; @@ -1466,12 +1480,14 @@ static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync, (void *)fi); if (!fi) { - res = asprintf(&buf, "/proc/self/fd/%i", lo_fd(req, ino)); + struct lo_data *lo = lo_data(req); + + res = asprintf(&buf, "%i", lo_fd(req, ino)); if (res == -1) { return (void)fuse_reply_err(req, errno); } - fd = open(buf, O_RDWR); + fd = openat(lo->proc_self_fd, buf, O_RDWR); free(buf); if (fd == -1) { return (void)fuse_reply_err(req, errno); @@ -1587,11 +1603,13 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi, static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, size_t size) { + struct lo_data *lo = lo_data(req); char *value = NULL; char procname[64]; struct lo_inode *inode; ssize_t ret; int saverr; + int fd = -1; inode = lo_inode(req, ino); if (!inode) { @@ -1616,7 +1634,11 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, goto out; } - sprintf(procname, "/proc/self/fd/%i", inode->fd); + sprintf(procname, "%i", inode->fd); + fd = openat(lo->proc_self_fd, procname, O_RDONLY); + if (fd < 0) { + goto out_err; + } if (size) { value = malloc(size); @@ -1624,7 +1646,7 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, goto out_err; } - ret = getxattr(procname, name, value, size); + ret = fgetxattr(fd, name, value, size); if (ret == -1) { goto out_err; } @@ -1635,7 +1657,7 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, fuse_reply_buf(req, value, ret); } else { - ret = getxattr(procname, name, NULL, 0); + ret = fgetxattr(fd, name, NULL, 0); if (ret == -1) { goto out_err; } @@ -1644,6 +1666,10 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, } out_free: free(value); + + if (fd >= 0) { + close(fd); + } return; out_err: @@ -1655,11 +1681,13 @@ out: static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) { + struct lo_data *lo = lo_data(req); char *value = NULL; char procname[64]; struct lo_inode *inode; ssize_t ret; int saverr; + int fd = -1; inode = lo_inode(req, ino); if (!inode) { @@ -1683,7 +1711,11 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) goto out; } - sprintf(procname, "/proc/self/fd/%i", inode->fd); + sprintf(procname, "%i", inode->fd); + fd = openat(lo->proc_self_fd, procname, O_RDONLY); + if (fd < 0) { + goto out_err; + } if (size) { value = malloc(size); @@ -1691,7 +1723,7 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) goto out_err; } - ret = listxattr(procname, value, size); + ret = flistxattr(fd, value, size); if (ret == -1) { goto out_err; } @@ -1702,7 +1734,7 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) fuse_reply_buf(req, value, ret); } else { - ret = listxattr(procname, NULL, 0); + ret = flistxattr(fd, NULL, 0); if (ret == -1) { goto out_err; } @@ -1711,6 +1743,10 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) } out_free: free(value); + + if (fd >= 0) { + close(fd); + } return; out_err: @@ -1724,9 +1760,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name, const char *value, size_t size, int flags) { char procname[64]; + struct lo_data *lo = lo_data(req); struct lo_inode *inode; ssize_t ret; int saverr; + int fd = -1; inode = lo_inode(req, ino); if (!inode) { @@ -1751,21 +1789,31 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name, goto out; } - sprintf(procname, "/proc/self/fd/%i", inode->fd); + sprintf(procname, "%i", inode->fd); + fd = openat(lo->proc_self_fd, procname, O_RDWR); + if (fd < 0) { + saverr = errno; + goto out; + } - ret = setxattr(procname, name, value, size, flags); + ret = fsetxattr(fd, name, value, size, flags); saverr = ret == -1 ? errno : 0; out: + if (fd >= 0) { + close(fd); + } fuse_reply_err(req, saverr); } static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name) { char procname[64]; + struct lo_data *lo = lo_data(req); struct lo_inode *inode; ssize_t ret; int saverr; + int fd = -1; inode = lo_inode(req, ino); if (!inode) { @@ -1789,12 +1837,20 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name) goto out; } - sprintf(procname, "/proc/self/fd/%i", inode->fd); + sprintf(procname, "%i", inode->fd); + fd = openat(lo->proc_self_fd, procname, O_RDWR); + if (fd < 0) { + saverr = errno; + goto out; + } - ret = removexattr(procname, name); + ret = fremovexattr(fd, name); saverr = ret == -1 ? errno : 0; out: + if (fd >= 0) { + close(fd); + } fuse_reply_err(req, saverr); } @@ -1887,12 +1943,25 @@ static void print_capabilities(void) printf("}\n"); } +static void setup_proc_self_fd(struct lo_data *lo) +{ + lo->proc_self_fd = open("/proc/self/fd", O_PATH); + if (lo->proc_self_fd == -1) { + fuse_log(FUSE_LOG_ERR, "open(/proc/self/fd, O_PATH): %m\n"); + exit(1); + } +} + int main(int argc, char *argv[]) { struct fuse_args args = FUSE_ARGS_INIT(argc, argv); struct fuse_session *se; struct fuse_cmdline_opts opts; - struct lo_data lo = { .debug = 0, .writeback = 0 }; + struct lo_data lo = { + .debug = 0, + .writeback = 0, + .proc_self_fd = -1, + }; struct lo_map_elem *root_elem; int ret = -1; @@ -2003,6 +2072,9 @@ int main(int argc, char *argv[]) fuse_daemonize(opts.foreground); + /* Must be after daemonize to get the right /proc/self/fd */ + setup_proc_self_fd(&lo); + /* Block until ctrl+c or fusermount -u */ ret = virtio_loop(se); @@ -2018,6 +2090,10 @@ err_out1: lo_map_destroy(&lo.dirp_map); lo_map_destroy(&lo.ino_map); + if (lo.proc_self_fd >= 0) { + close(lo.proc_self_fd); + } + if (lo.root.fd >= 0) { close(lo.root.fd); }