From: Stefan Hajnoczi <stefa...@redhat.com> 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 <stefa...@redhat.com> --- tools/virtiofsd/passthrough_ll.c | 59 ++++++++++++++++++++++++++++---- 1 file changed, 53 insertions(+), 6 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 1faae2753f..84e9d8916f 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -133,6 +133,21 @@ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n); static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st); +static int is_dot_or_dotdot(const char *name) +{ + return name[0] == '.' && + (name[1] == '\0' || (name[1] == '.' && name[2] == '\0')); +} + +/* Is `path` a single path component that is not "." or ".."? */ +static int is_safe_path_component(const char *path) +{ + if (strchr(path, '/')) { + return 0; + } + + return !is_dot_or_dotdot(path); +} static struct lo_data *lo_data(fuse_req_t req) { @@ -681,6 +696,15 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) parent, name); } + /* + * Don't use is_safe_path_component(), allow "." and ".." for NFS export + * support. + */ + if (strchr(name, '/')) { + fuse_reply_err(req, EINVAL); + return; + } + err = lo_do_lookup(req, parent, name, &e); if (err) { fuse_reply_err(req, err); @@ -745,6 +769,11 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, struct fuse_entry_param e; struct lo_cred old = {}; + if (!is_safe_path_component(name)) { + fuse_reply_err(req, EINVAL); + return; + } + dir = lo_inode(req, parent); if (!dir) { fuse_reply_err(req, EBADF); @@ -846,6 +875,11 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, struct fuse_entry_param e; int saverr; + if (!is_safe_path_component(name)) { + fuse_reply_err(req, EINVAL); + return; + } + inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); @@ -887,6 +921,10 @@ out_err: static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name) { int res; + if (!is_safe_path_component(name)) { + fuse_reply_err(req, EINVAL); + return; + } res = unlinkat(lo_fd(req, parent), name, AT_REMOVEDIR); @@ -899,6 +937,11 @@ static void lo_rename(fuse_req_t req, fuse_ino_t parent, const char *name, { int res; + if (!is_safe_path_component(name) || !is_safe_path_component(newname)) { + fuse_reply_err(req, EINVAL); + return; + } + if (flags) { fuse_reply_err(req, EINVAL); return; @@ -913,6 +956,11 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name) { int res; + if (!is_safe_path_component(name)) { + fuse_reply_err(req, EINVAL); + return; + } + res = unlinkat(lo_fd(req, parent), name, 0); fuse_reply_err(req, res == -1 ? errno : 0); @@ -1076,12 +1124,6 @@ out_err: fuse_reply_err(req, error); } -static int is_dot_or_dotdot(const char *name) -{ - return name[0] == '.' && - (name[1] == '\0' || (name[1] == '.' && name[2] == '\0')); -} - static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset, struct fuse_file_info *fi, int plus) { @@ -1231,6 +1273,11 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, parent, name); } + if (!is_safe_path_component(name)) { + fuse_reply_err(req, EINVAL); + return; + } + err = lo_change_cred(req, &old); if (err) { goto out; -- 2.23.0