36f1b16b0
Denys Vlasenko
2025-08-17
Subject
hush: fix infinite loop expanding alias a="nice&&a"
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shell/hush.c+45 -6
| @@ -2937,14 +2937,29 @@ static void i_prepend_to_alias_buffer(struct in_str *i, char *prepend, char ch) | |
| } | |
| i->saved_ibuf = i->p; | |
| i->p = i->albuf = xasprintf("%s%c", prepend, ch); | |
| + | //bb_error_msg("albuf'%s'", i->albuf); |
| } | |
| static void i_free_alias_buffer(struct in_str *i) | |
| { | |
| if (i->saved_ibuf) { | |
| - | /* We are here if there was an alias expansion and it has ended just now */ |
| + | /* We are here if alias expansion has ended just now */ |
| free(i->albuf); | |
| i->p = i->saved_ibuf; | |
| i->saved_ibuf = NULL; | |
| + | /* We re-enable aliases only if expansion has finished, not on command boundaries. |
| + | * Example: |
| + | * alias a="nice&&a" |
| + | * a;a |
| + | * This should run "nice" and then "can't execute 'a': No such file or directory", |
| + | * then should run "nice" again and then "can't execute 'a': No such file or directory" again |
| + | * because the second "a" in alias definition must not expand (to prevent infinite expansion), |
| + | * but the "a" after ; must expand (there is no danger of infinite expansion). |
| + | * alias a="nice&&nice" |
| + | * a;a&&a |
| + | * should execute "nice" six times. |
| + | */ |
| + | debug_printf_parse("end of alias\n"); |
| + | enable_all_aliases(); |
| } | |
| } | |
| #else | |
| @@ -3015,6 +3030,16 @@ static int i_peek(struct in_str *i) | |
| if (i->p) { | |
| /* string-based in_str, or line editing buffer, or alias buffer */ | |
| + | #if ENABLE_HUSH_ALIAS |
| + | if (*i->p == '\0' && i->saved_ibuf) { |
| + | /* corner case: "an_alias&&..." expansion will have |
| + | * i->p = "<alias_expansion>&", i->saved_ibuf = "&..." |
| + | * and at the end of it, we must not return NUL, |
| + | * this would logically split && into & & during parsing. |
| + | */ |
| + | return (unsigned char)*i->saved_ibuf; |
| + | } |
| + | #endif |
| return (unsigned char)*i->p; | |
| } | |
| @@ -6273,8 +6298,6 @@ static struct pipe *parse_stream(char **pstring, | |
| ctx.ctx_res_w = RES_MATCH; /* "we are in PATTERN)" */ | |
| } | |
| #endif | |
| - | finished_cmd_reenable_aliases: |
| - | enable_all_aliases(); /* try: { an_alias; an_alias; } */ |
| finished_cmd: | |
| /* We just finished a cmd. New one may start | |
| * with an assignment */ | |
| @@ -6282,6 +6305,14 @@ static struct pipe *parse_stream(char **pstring, | |
| debug_printf_parse("ctx.is_assignment='%s'\n", assignment_flag[ctx.is_assignment]); | |
| continue; /* get next char */ | |
| case '&': | |
| + | #if ENABLE_HUSH_ALIAS |
| + | /* Check for alias expansion (only for first word of command) */ |
| + | if (G_interactive_fd && !ctx.command->argv) { |
| + | alias = word_matches_alias(&ctx); |
| + | if (alias) |
| + | goto add_to_albuf_and_get_next_char; |
| + | } |
| + | #endif |
| if (done_word(&ctx)) | |
| goto parse_error_exitcode1; | |
| if (ctx.pipe->num_cmds == 0 && IS_NULL_CMD(ctx.command)) { | |
| @@ -6305,7 +6336,7 @@ static struct pipe *parse_stream(char **pstring, | |
| goto parse_error_exitcode1; | |
| } | |
| } | |
| - | goto finished_cmd_reenable_aliases; /* try: an_alias &[&] an_alias */ |
| + | goto finished_cmd; |
| case '|': | |
| #if ENABLE_HUSH_CASE | |
| if (ctx.ctx_res_w == RES_MATCH) { | |
| @@ -6320,6 +6351,14 @@ static struct pipe *parse_stream(char **pstring, | |
| goto parse_error_exitcode1; | |
| continue; /* get next char */ | |
| } | |
| + | #endif |
| + | #if ENABLE_HUSH_ALIAS |
| + | /* Check for alias expansion (only for first word of command) */ |
| + | if (G_interactive_fd && !ctx.command->argv) { |
| + | alias = word_matches_alias(&ctx); |
| + | if (alias) |
| + | goto add_to_albuf_and_get_next_char; |
| + | } |
| #endif | |
| if (done_word(&ctx)) | |
| goto parse_error_exitcode1; | |
| @@ -6345,7 +6384,7 @@ static struct pipe *parse_stream(char **pstring, | |
| } | |
| done_command(&ctx); | |
| } | |
| - | goto finished_cmd_reenable_aliases; /* try: an_alias |[|] an_alias */ |
| + | goto finished_cmd; |
| case '(': | |
| #if ENABLE_HUSH_CASE | |
| /* "case... in (PATTERNS)..."? */ | |
| @@ -6364,7 +6403,7 @@ static struct pipe *parse_stream(char **pstring, | |
| goto parse_error_exitcode1; | |
| debug_printf_heredoc("parse_group done, needs heredocs:%d\n", n); | |
| heredoc_cnt += n; | |
| - | goto finished_cmd_reenable_aliases; |
| + | goto finished_cmd; |
| } | |
| case ')': | |
| #if ENABLE_HUSH_CASE | |