Configuration Information [Automatically generated, do not change]: Machine: x86_64 OS: linux-gnu Compiler: gcc Compilation CFLAGS: -march=native -O3 uname output: Linux chatoyancy 5.6.13-100.fc30.x86_64 #1 SMP Fri May 15 00:36:06 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux Machine Type: x86_64-pc-linux-gnu
Bash Version: 5.1
Patch Level: 0
Release Status: release
Description:
When a command string with an incomplete construct is supplied to
the `eval' builtin in interactive sessions, the process will be
terminated. This does not happen before Bash 5.0. This does not
happen in non-interactive modes.
Repeat-By:
The entire interactive session ends with `eval {'.
bash-5.0$ eval {
bash-5.0: syntax error: unexpected end of file
exit
This does not happen in bash-4.4 and before. The session will not
close, and one can enter and execute the next command.
bash-4.4$ eval {
bash-4.4: syntax error: unexpected end of file
bash-4.4$ echo $?
1
bash-4.4$
This also happens when `eval {' is executed in a function. The
session closes.
bash-5.0$ function fun { eval {; }
bash-5.0$ fun
bash-5.0: syntax error: unexpected end of file
exit
This does not happen when `eval {' is executed in the
non-interactive mode. The commands following `eval {' will be
executed as normal.
bash-5.0$ cat test18.sh
echo Begin eval
eval {
echo End eval
bash-5.0$ bash-5.0 test18.sh
Begin eval
test18.sh: eval: line 2: syntax error: unexpected end of file
End eval
bash-5.0$ . test18.sh
Begin eval
test18.sh: eval: line 2: syntax error: unexpected end of file
End eval
Fix:
* This behavior has been introduced in `parse.y' in commit 8a10051
(commit bash-20170511 snapshot) to solve the infinite loop found by
fuzzing reported at
https://lists.gnu.org/archive/html/bug-bash/2017-05/msg00076.html.
I extracted the related section of the commit change:
> From 8a100514480a55ad73966e516e38778509f6ace6 Mon Sep 17 00:00:00 2001
> From: Chet Ramey <chet.ra...@case.edu>
> Date: Thu, 11 May 2017 14:45:50 -0400
> Subject: [PATCH] commit bash-20170511 snapshot
>
> diff --git a/CWRU/CWRU.chlog b/CWRU/CWRU.chlog
> index 7892ce94..8ea60a39 100644
> --- a/CWRU/CWRU.chlog
> +++ b/CWRU/CWRU.chlog
> @@ -13840,3 +13840,18 @@ builtins/read.def
> a CTLESC the last time through the loop (skip_ctlesc == 0),
> especially if i == 0. Another fuzzing bug from Eduardo Bustamante
> <dual...@gmail.com>
> +
> + 5/9
> + ---
> +parse.y
> + - GRAMMAR: add 'error yacc_EOF' production to handle a syntax error
> + that's immediately followed by an EOF after resynchronization.
> + Fixes another fuzzing bug
> diff --git a/parse.y b/parse.y
> index 7ca4a64e..dcc628e7 100644
> --- a/parse.y
> +++ b/parse.y
> @@ -411,7 +411,14 @@ inputunit: simple_list simple_list_terminator
> YYABORT;
> }
> }
> + | error yacc_EOF
> + {
> + /* EOF after an error. Do ignoreeof or not. Really
> + only interesting in non-interactive shells */
> + global_command = (COMMAND *)NULL;
> + handle_eof_input_unit ();
> + YYACCEPT;
> + }
> | yacc_EOF
> {
> /* Case of EOF seen by itself. Do ignoreeof or
> --
> 2.21.3
The problem here is that `handle_eof_input_unit' terminates the
entire shell when it is in the interactive mode even when the shell
is processing the string passed to `eval' command.
The special treatment of EOF for exiting shell should be processed
only when the shell processes the top-level commands (i.e., not the
command strings executed through `eval', etc.)
I attach a patch for the devel branch (see
0001-Fix-a-bug-that-syntax-errors-in-eval-causes-the-inte.patch). I
moved the position of the line `handle_eof_input_unit ();' so that
it is only executed when `parse_and_execute_level == 0'.
[ Note: The current code in `parse.y' has additional fixes after
2017-05-09, so the code looks slightly different from that in the
commit 2017-05-09 [for details, see Appendix A below], but the `eval
{' problem is still present. ]
--
Koichi
----------------------------------------------------------------------
Appendix A:
One of the fix has been made to solve another problem introduced by
2017-05-09 fix: Even in non-interactive modes, the exit status of
`eval {' becomes 0 althogh it prints the error messages of syntax
errors. This second problem has been already reported by Martijn at
https://lists.gnu.org/archive/html/bug-bash/2017-06/msg00236.html
The fix to this second problem has been made in the commit d7d836dfc
(commit bash-snap-20170620 snapshot). I extract the corresponding
section:
> From d7d836dfc55b937f463f601ba5117d6442053089 Mon Sep 17 00:00:00 2001
> From: Chet Ramey <chet.ra...@case.edu>
> Date: Tue, 20 Jun 2017 10:38:13 -0400
> Subject: [PATCH] commit bash-snap-20170620 snapshot
>
> diff --git a/CWRU/CWRU.chlog b/CWRU/CWRU.chlog
> index 31724be0..7dd09a3f 100644
> --- a/CWRU/CWRU.chlog
> +++ b/CWRU/CWRU.chlog
> @@ -14102,3 +14102,11 @@ parse.y
> lib/readline/display.c
> - update_line: when wrapping multibyte characters, make sure we deal
> with WCWIDTH returning -1. Fixes a fuzzing bug
> +
> + 6/17
> + ----
> +parse.y
> + - augment `error yacc_EOF' production to call YYABORT in non-interactive
> + shells or calls to parse_and_execute (eval, command substitution,
> + etc.) Fixes bug reported by Martijn Dekker <mart...@inlv.org>
> +
> diff --git a/parse.y b/parse.y
> index d8d8e885..92da96b9 100644
> --- a/parse.y
> +++ b/parse.y
> @@ -416,9 +416,16 @@ inputunit: simple_list simple_list_terminator
> /* EOF after an error. Do ignoreeof or not. Really
> only interesting in non-interactive shells */
> global_command = (COMMAND *)NULL;
> + last_command_exit_value = 1;
> handle_eof_input_unit ();
> - YYACCEPT;
> + if (interactive && parse_and_execute_level == 0)
> + {
> + YYACCEPT;
> + }
> + else
> + {
> + YYABORT;
> + }
> }
> | yacc_EOF
> {
> --
> 2.21.3
Further lines are added in the commit ab8ded9c3 (commit
bash-20181214 snapshot), but this change is not relevant for now, so
I skip the details of the commit.
----------------------------------------------------------------------
0001-Fix-a-bug-that-syntax-errors-in-eval-causes-the-inte.patch
Description: Binary data
