diff -rup vim74/src/option.c vim74-new/src/option.c --- vim74/src/option.c 2013-07-17 12:39:13.000000000 -0700 +++ vim74-new/src/option.c 2016-11-28 16:59:31.763889780 -0800 @@ -5653,6 +5653,21 @@ set_string_option(opt_idx, value, opt_fl } /* + * Return TRUE if "val" is a valid 'filetype' name. + * Also used for 'syntax' and 'keymap'. + */ + static int +valid_filetype(char_u *val) +{ + char_u *s; + + for (s = val; *s != NUL; ++s) + if (!ASCII_ISALNUM(*s) && vim_strchr((char_u *)".-_", *s) == NULL) + return FALSE; + return TRUE; +} + +/* * Handle string options that need some action to perform when changed. * Returns NULL for success, or an error message for an error. */ @@ -6043,8 +6058,11 @@ did_set_string_option(opt_idx, varp, new #ifdef FEAT_KEYMAP else if (varp == &curbuf->b_p_keymap) { - /* load or unload key mapping tables */ - errmsg = keymap_init(); + if (!valid_filetype(*varp)) + errmsg = e_invarg; + else + /* load or unload key mapping tables */ + errmsg = keymap_init(); if (errmsg == NULL) { @@ -6990,6 +7008,22 @@ did_set_string_option(opt_idx, varp, new } #endif +#ifdef FEAT_AUTOCMD + else if (gvarp == &p_ft) + { + if (!valid_filetype(*varp)) + errmsg = e_invarg; + } +#endif + +#ifdef FEAT_SYN_HL + else if (gvarp == &p_syn) + { + if (!valid_filetype(*varp)) + errmsg = e_invarg; + } +#endif + /* Options that are a list of flags. */ else {