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Fix blocked signals after fork(2)ing external command in subshell

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When the classic fork/exec mechanism was used (via sh_fork()) to
run an external command from within a non-forking subshell, SIGINT
was blocked until that subshell was exited. If a subsequent loop
was run in the subshell, it became uninterruptible, e.g.:

   $ arch/*/bin/ksh -c '(/usr/bin/true; while :; do :; done); exit'
   ^C^C^C^C^C

src/cmd/ksh93/sh/xec.c:
- sh_fork() did not reset the savesig variable in the parent part
  of the fork when running in a virtual subshell. This had the
  effect of delaying signal handling until exiting the subshell.
  There is no reason for that subshell check that I can discern, so
  this removes it.
      I've verified that this causes no regression test failures
  even when ksh is compiled with -DSHOPT_SPAWN=0 which means the
  classic fork/exec mechanism is always used.

Fixes: https://github.com/ksh93/ksh/issues/86
This commit is contained in:
Martijn Dekker 2020-07-30 01:22:11 +01:00
parent 56fe602800
commit 70f6d758c0
3 changed files with 11 additions and 8 deletions
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6
NEWS
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@ -3,6 +3,12 @@ For full details, see the git log at: https://github.com/ksh93/ksh
Any uppercase BUG_* names are modernish shell bug IDs. Any uppercase BUG_* names are modernish shell bug IDs.
2020-07-29:
- On a ksh compiled to use fork(2) to run external commands, a bug has been
fixed that caused signals (such as SIGINT, Ctrl+C) to be ignored within a
non-forked subshell after running an external command within that subshell.
2020-07-25: 2020-07-25:
- Fixed BUG_MULTIBIFS: Multibyte characters can now be used as IFS - Fixed BUG_MULTIBIFS: Multibyte characters can now be used as IFS

2
src/cmd/ksh93/include/version.h
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@ -17,4 +17,4 @@
* David Korn <dgk@research.att.com> * * David Korn <dgk@research.att.com> *
* * * *
***********************************************************************/ ***********************************************************************/
#define SH_RELEASE "93u+m 2020-07-25" #define SH_RELEASE "93u+m 2020-07-29"

11
src/cmd/ksh93/sh/xec.c
View file

@ -2951,13 +2951,10 @@ pid_t sh_fork(Shell_t *shp,int flags, int *jobid)
shp->savesig = -1; shp->savesig = -1;
while(_sh_fork(shp,parent=fork(),flags,jobid) < 0); while(_sh_fork(shp,parent=fork(),flags,jobid) < 0);
sh_stats(STAT_FORKS); sh_stats(STAT_FORKS);
if(!shp->subshell) sig = shp->savesig;
{ shp->savesig = 0;
sig = shp->savesig; if(sig>0)
shp->savesig = 0; kill(getpid(),sig);
if(sig>0)
kill(getpid(),sig);
}
job_fork(parent); job_fork(parent);
return(parent); return(parent);
} }