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Invocation: fix infinite loop on 'ksh +s'

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When starting ksh +s, it gets stuck in an infinite loop continually
trying to parse its own binary as a shell script and rejecting it:

$ arch/linux.i386-64/bin/ksh +s
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
[...]
$ echo 'echo "this is stdin"' | arch/linux.i386-64/bin/ksh +s
arch/linux.i386-64/bin/ksh: arch/linux.i386-64/bin/ksh: cannot execute [Exec format error]
(no loop, but still ksh trying to parse itself)

src/cmd/ksh93/sh/init.c: sh_init():
- When forcing on the '-s' option upon finding no command
  arguments, also update sh.offoptions, a.k.a. shp->offoptions.
  This avoids the inconsistent state causing this problem.

  In main.c, there is:

  if(sh_isoption(SH_SFLAG))
      fdin = 0;
  else
      (code to open $0 as a file)

  This was entering the else block because sh_isoption(SH_SFLAG)
  was returning 0, and $0 is set to the ksh binary as it is
  supposed to when no other script is provided. When I looked for
  why sh_isoption was returning 0, I found main.c's

  for(i=0; i<elementsof(shp->offoptions.v); i++)
      shp->options.v[i] &= ~shp->offoptions.v[i];

  Before this loop, shp->offoptions tracks which options were
  explicitly disabled by the user on the command line. The effect
  of this loop is to make "explicitly disabled" take precedence
  over "implicitly enabled". My patch removes the registration of
  the +s option.

Fixes: https://github.com/ksh93/ksh/issues/150
Co-authored-by: Martijn Dekker <martijn@inlv.org>
This commit is contained in:
Harald van Dijk 2021-01-03 23:54:36 +00:00 • committed by Martijn Dekker
parent 737438a30f
commit 41ef7f76cf
5 changed files with 14 additions and 3 deletions
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@ -3,6 +3,14 @@ For full details, see the git log at: https://github.com/ksh93/ksh
Any uppercase BUG_* names are modernish shell bug IDs.
2021-01-03:
- The invocation
$ ksh +s
caused an infinite loop and corrupted ~/.sh_history. This is now fixed so
that the '-s' option is automatically turned on if there are no non-option
command arguments, as documented in Bolsky & Korn (1995), p. 261.
2020-10-22:
- Fixed: 'typeset -F0', 'typeset -E0', and 'typeset -X0' floating point