On Wed, Feb 17, 2021 at 06:30:44PM -0500, Vivek Goyal wrote: > fuse has an option FUSE_POSIX_ACL which needs to be opted in by fuse > server to enable posix acls. > > Add virtiofsd option "-o posix_acl/no_posix_acl" to let users enable/disable > posix acl support. By default it is disabled as of now. > > Currently even if file server has not opted in for FUSE_POSIX_ACL, user can > still query acl and set acl, and system.posix_acl_access and > system.posix_acl_default xattrs show up listxattr response. > > Miklos said this is confusing. So he said lets block and filter > system.posix_acl_access and system.posix_acl_default xattrs in > getxattr/setxattr/listxattr if user has explicitly disabled > posix acls using -o no_posix_acl.
I forgot to block acl xattrs in lo_removexattr(). Will respin this patch. Vivek > > As of now continuing to keeping the existing behavior if user did not > specify any option to disable acl support due to concerns about backward > compatibility. > > v2: block system.posix_acl_access and system.posix_acl_default xattrs > if user explicitly disabled acls. (Miklos) > > Signed-off-by: Vivek Goyal <[email protected]> > --- > tools/virtiofsd/passthrough_ll.c | 95 +++++++++++++++++++++++++++++++- > 1 file changed, 94 insertions(+), 1 deletion(-) > > diff --git a/tools/virtiofsd/passthrough_ll.c > b/tools/virtiofsd/passthrough_ll.c > index 58d24c0010..26cdfbd1f0 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -169,6 +169,7 @@ struct lo_data { > /* An O_PATH file descriptor to /proc/self/fd/ */ > int proc_self_fd; > int user_killpriv_v2, killpriv_v2; > + int user_posix_acl; > }; > > static const struct fuse_opt lo_opts[] = { > @@ -201,6 +202,8 @@ static const struct fuse_opt lo_opts[] = { > { "announce_submounts", offsetof(struct lo_data, announce_submounts), 1 > }, > { "killpriv_v2", offsetof(struct lo_data, user_killpriv_v2), 1 }, > { "no_killpriv_v2", offsetof(struct lo_data, user_killpriv_v2), 0 }, > + { "posix_acl", offsetof(struct lo_data, user_posix_acl), 1 }, > + { "no_posix_acl", offsetof(struct lo_data, user_posix_acl), 0 }, > FUSE_OPT_END > }; > static bool use_syslog = false; > @@ -661,6 +664,23 @@ static void lo_init(void *userdata, struct > fuse_conn_info *conn) > conn->want &= ~FUSE_CAP_HANDLE_KILLPRIV_V2; > lo->killpriv_v2 = 0; > } > + > + if (lo->user_posix_acl == 1) { > + /* > + * User explicitly asked for this option. Enable it unconditionally. > + * If connection does not have this capability, it should fail > + * in fuse_lowlevel.c > + */ > + fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling posix acl\n"); > + conn->want |= FUSE_CAP_POSIX_ACL; > + } else { > + /* > + * Either user specified to disable posix_acl, or did not specify > + * anything. In both the cases do not enable posix acl. > + */ > + fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling posix_acl\n"); > + conn->want &= ~FUSE_CAP_POSIX_ACL; > + } > } > > static void lo_getattr(fuse_req_t req, fuse_ino_t ino, > @@ -2612,6 +2632,63 @@ static int xattr_map_server(const struct lo_data *lo, > const char *server_name, > return -ENODATA; > } > > +static bool block_xattr(struct lo_data *lo, const char *name) > +{ > + /* > + * If user explicitly enabled posix_acl or did not provide any option, > + * do not block acl. Otherwise block system.posix_acl_access and > + * system.posix_acl_default xattrs. > + */ > + if (lo->user_posix_acl) { > + return false; > + } > + if (!strcmp(name, "system.posix_acl_access") || > + !strcmp(name, "system.posix_acl_default")) > + return true; > + > + return false; > +} > + > +/* > + * Returns number of bytes in xattr_list after filtering on success. This > + * could be zero as well if nothing is left after filtering. > + * > + * Returns negative error code on failure. > + * xattr_list is modified in place. > + */ > +static int remove_blocked_xattrs(struct lo_data *lo, char *xattr_list, > + unsigned in_size) > +{ > + size_t out_index, in_index; > + > + /* > + * As of now we only filter out acl xattrs. If acls are enabled or > + * they have not been explicitly disabled, there is nothing to > + * filter. > + */ > + if (lo->user_posix_acl) { > + return in_size; > + } > + > + out_index = 0; > + in_index = 0; > + while (in_index < in_size) { > + char *in_ptr = xattr_list + in_index; > + > + /* Length of current attribute name */ > + size_t in_len = strlen(xattr_list + in_index) + 1; > + > + if (!block_xattr(lo, in_ptr)) { > + if (in_index != out_index) { > + memmove(xattr_list + out_index, xattr_list + in_index, > in_len); > + } > + out_index += in_len; > + } > + in_index += in_len; > + } > + return out_index; > +} > + > static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, > size_t size) > { > @@ -2625,6 +2702,11 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t > ino, const char *in_name, > int saverr; > int fd = -1; > > + if (block_xattr(lo, in_name)) { > + fuse_reply_err(req, EOPNOTSUPP); > + return; > + } > + > mapped_name = NULL; > name = in_name; > if (lo->xattrmap) { > @@ -2766,7 +2848,6 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t > ino, size_t size) > if (ret == 0) { > goto out; > } > - > if (lo->xattr_map_list) { > /* > * Map the names back, some attributes might be dropped, > @@ -2813,6 +2894,12 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t > ino, size_t size) > goto out; > } > } > + > + ret = remove_blocked_xattrs(lo, value, ret); > + if (ret <= 0) { > + saverr = -ret; > + goto out; > + } > fuse_reply_buf(req, value, ret); > } else { > /* > @@ -2851,6 +2938,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t > ino, const char *in_name, > int saverr; > int fd = -1; > > + if (block_xattr(lo, in_name)) { > + fuse_reply_err(req, EOPNOTSUPP); > + return; > + } > + > mapped_name = NULL; > name = in_name; > if (lo->xattrmap) { > @@ -3604,6 +3696,7 @@ int main(int argc, char *argv[]) > .allow_direct_io = 0, > .proc_self_fd = -1, > .user_killpriv_v2 = -1, > + .user_posix_acl = -1, > }; > struct lo_map_elem *root_elem; > struct lo_map_elem *reserve_elem; > -- > 2.25.4 >
