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| author | Denys Vlasenko | 2021-09-09 16:26:41 +0200 |
|---|---|---|
| committer | Denys Vlasenko | 2021-09-09 16:29:37 +0200 |
| commit | eb607777697f4c5eb2dfd86e5837a8c379f65979 (patch) | |
| tree | b623e6d90bd7a2dfdb2e48226e3c4757e11affdd | |
| parent | 48cb983b136fb74c61db594a30e18bdc42b7264c (diff) | |
| download | busybox-eb607777697f4c5eb2dfd86e5837a8c379f65979.zip busybox-eb607777697f4c5eb2dfd86e5837a8c379f65979.tar.gz | |
ash: eval: Prevent recursive PS4 expansion
Date: Wed, 27 May 2020 13:19:10 +1000
eval: Prevent recursive PS4 expansion
Yaroslav Halchenko <yoh@onerussian.com> wrote:
> I like to (ab)use PS4 and set -x for tracing execution of scripts.
> Reporting time and PID is very useful in this context.
>
> I am not 100% certain if bash's behavior (of actually running the command
> embedded within PS4 string, probably eval'ing it) is actually POSIX
> compliant, posh seems to not do that; but I think it is definitely not
> desired for dash to just stall:
>
> - the script:
> #!/bin/sh
> set -x
> export PS4='+ $(date +%T.%N) [$$] '
> echo "lets go"
> sleep 1
> echo "done $var"
>
> - bash:
> /tmp > bash --posix test.sh
> +export 'PS4=+ $(date +%T.%N) [$$] '
> +PS4='+ $(date +%T.%N) [$$] '
> + 09:15:48.982296333 [2764323] echo 'lets go'
> lets go
> + 09:15:48.987829613 [2764323] sleep 1
> + 09:15:49.994485037 [2764323] echo 'done '
> done
>
...
> - dash: (stalls it set -x)
> /tmp > dash test.sh
> +export PS4=+ $(date +%T.%N) [$$]
> ^C^C
This patch fixes the infinite loop caused by repeated expansions
of PS4.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -rw-r--r-- | shell/ash.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/shell/ash.c b/shell/ash.c index ba116d8..3524d04 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -404,6 +404,7 @@ struct globals_misc { uint8_t exitstatus; /* exit status of last command */ uint8_t back_exitstatus;/* exit status of backquoted command */ smallint job_warning; /* user was warned about stopped jobs (can be 2, 1 or 0). */ + smallint inps4; /* Prevent PS4 nesting. */ int savestatus; /* exit status of last command outside traps */ int rootpid; /* pid of main shell */ /* shell level: 0 for the main shell, 1 for its children, and so on */ @@ -492,6 +493,7 @@ extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc; #define exitstatus (G_misc.exitstatus ) #define back_exitstatus (G_misc.back_exitstatus ) #define job_warning (G_misc.job_warning) +#define inps4 (G_misc.inps4 ) #define savestatus (G_misc.savestatus ) #define rootpid (G_misc.rootpid ) #define shlvl (G_misc.shlvl ) @@ -10423,10 +10425,12 @@ evalcommand(union node *cmd, int flags) } /* Print the command if xflag is set. */ - if (xflag) { + if (xflag && !inps4) { const char *pfx = ""; + inps4 = 1; fdprintf(preverrout_fd, "%s", expandstr(ps4val(), DQSYNTAX)); + inps4 = 0; sp = varlist.list; while (sp) { @@ -14323,6 +14327,7 @@ exitreset(void) } evalskip = 0; loopnest = 0; + inps4 = 0; /* from expand.c: */ ifsfree(); |