virtiofsd: validate path components
Several FUSE requests contain single path components. A correct FUSE client sends well-formed path components but there is currently no input validation in case something went wrong or the client is malicious. Refuse ".", "..", and paths containing '/' when we expect a path component. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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@ -133,6 +133,21 @@ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n);
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static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st);
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static int is_dot_or_dotdot(const char *name)
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{
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return name[0] == '.' &&
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(name[1] == '\0' || (name[1] == '.' && name[2] == '\0'));
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}
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/* Is `path` a single path component that is not "." or ".."? */
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static int is_safe_path_component(const char *path)
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{
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if (strchr(path, '/')) {
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return 0;
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}
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return !is_dot_or_dotdot(path);
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}
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static struct lo_data *lo_data(fuse_req_t req)
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{
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@ -681,6 +696,15 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
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parent, name);
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}
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/*
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* Don't use is_safe_path_component(), allow "." and ".." for NFS export
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* support.
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*/
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if (strchr(name, '/')) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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err = lo_do_lookup(req, parent, name, &e);
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if (err) {
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fuse_reply_err(req, err);
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@ -762,6 +786,11 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
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struct fuse_entry_param e;
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struct lo_cred old = {};
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if (!is_safe_path_component(name)) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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dir = lo_inode(req, parent);
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if (!dir) {
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fuse_reply_err(req, EBADF);
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@ -863,6 +892,11 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent,
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struct fuse_entry_param e;
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int saverr;
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if (!is_safe_path_component(name)) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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inode = lo_inode(req, ino);
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if (!inode) {
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fuse_reply_err(req, EBADF);
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@ -904,6 +938,10 @@ out_err:
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static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name)
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{
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int res;
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if (!is_safe_path_component(name)) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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res = unlinkat(lo_fd(req, parent), name, AT_REMOVEDIR);
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@ -916,6 +954,11 @@ static void lo_rename(fuse_req_t req, fuse_ino_t parent, const char *name,
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{
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int res;
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if (!is_safe_path_component(name) || !is_safe_path_component(newname)) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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if (flags) {
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fuse_reply_err(req, EINVAL);
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return;
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@ -930,6 +973,11 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name)
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{
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int res;
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if (!is_safe_path_component(name)) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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res = unlinkat(lo_fd(req, parent), name, 0);
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fuse_reply_err(req, res == -1 ? errno : 0);
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@ -1093,12 +1141,6 @@ out_err:
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fuse_reply_err(req, error);
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}
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static int is_dot_or_dotdot(const char *name)
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{
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return name[0] == '.' &&
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(name[1] == '\0' || (name[1] == '.' && name[2] == '\0'));
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}
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static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
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off_t offset, struct fuse_file_info *fi, int plus)
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{
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@ -1248,6 +1290,11 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
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parent, name);
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}
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if (!is_safe_path_component(name)) {
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fuse_reply_err(req, EINVAL);
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return;
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}
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err = lo_change_cred(req, &old);
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if (err) {
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goto out;
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