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cd - shouldn't ignore $OLDPWD when in a new scope (#249)

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This bug was first reported at <https://github.com/att/ast/issues/8>.
The 'cd' command currently takes the value of $OLDPWD from the
wrong scope. In the following example 'cd -' will change the
directory to /bin instead of /tmp:

    $ OLDPWD=/bin ksh93 -c 'OLDPWD=/tmp cd -'
    /bin

src/cmd/ksh93/bltins/cd_pwd.c:
- Use sh_scoped() to obtain the correct value of $OLDPWD.
- Fix a use-after-free bug. Make the 'oldpwd' variable a static
  char that points to freeable memory. Each time cd is used, this
  variable is freed if it points to a freeable memory address and
  isn't also a pointer to shp->pwd.

src/cmd/ksh93/sh/path.c: path_pwd():
- Simplify and add comments.
- Scope $PWD properly.

src/cmd/ksh93/tests/builtins.sh,
src/cmd/ksh93/tests/leaks.sh:
- Backport the ksh2020 regression tests for 'cd -' when $OLDPWD is
  set.
- Add test for $OLDPWD and $PWD after subshare.
- Add test for $PWD after 'cd'.
- Add test for possible memory leak.
- Add testing for 'unset' on OLDPWD and PWD.

src/cmd/ksh93/COMPATIBILITY:
- Add compatibility note about changes to $PWD and $OLDPWD.

Co-authored-by: Martijn Dekker <martijn@inlv.org>
This commit is contained in:
Johnothan King 2021-04-01 17:19:19 -07:00 • committed by GitHub
parent ed478ab7e3
commit ca2443b58c
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7 changed files with 148 additions and 41 deletions
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56
src/cmd/ksh93/sh/path.c
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@ -244,49 +244,35 @@ static pid_t path_xargs(Shell_t *shp,const char *path, char *argv[],char *const
char *path_pwd(Shell_t *shp,int flag)
{
register char *cp;
register int count = 0;
Namval_t *pwdnod;
NOT_USED(flag);
/* Don't bother if PWD already set */
if(shp->pwd)
return((char*)shp->pwd);
while(1)
/* First see if PWD variable is correct */
pwdnod = sh_scoped(shp,PWDNOD);
cp = nv_getval(pwdnod);
if(!(cp && *cp=='/' && test_inode(cp,e_dot)))
{
/* try from lowest to highest */
switch(count++)
/* Check if $HOME is a path to the PWD; this ensures $PWD == $HOME
at login, even if $HOME is a path that contains symlinks */
cp = nv_getval(sh_scoped(shp,HOME));
if(!(cp && *cp=='/' && test_inode(cp,e_dot)))
{
case 0:
cp = nv_getval(PWDNOD);
break;
case 1:
cp = nv_getval(HOME);
break;
case 2:
cp = "/";
break;
case 3:
{
if(cp=getcwd(NIL(char*),0))
{
nv_offattr(PWDNOD,NV_NOFREE);
_nv_unset(PWDNOD,0);
PWDNOD->nvalue.cp = cp;
goto skip;
}
break;
}
case 4:
/* Get physical PWD (no symlinks) using getcwd(3), fall back to "." */
cp = getcwd(NIL(char*),0);
if(!cp)
return((char*)e_dot);
}
if(cp && *cp=='/' && test_inode(cp,e_dot))
break;
/* Store in PWD variable */
if(shp->subshell)
pwdnod = sh_assignok(pwdnod,1);
nv_offattr(pwdnod,NV_NOFREE);
nv_putval(pwdnod,cp,NV_RDONLY);
}
if(count>1)
{
nv_offattr(PWDNOD,NV_NOFREE);
nv_putval(PWDNOD,cp,NV_RDONLY);
}
skip:
nv_onattr(PWDNOD,NV_NOFREE|NV_EXPORT);
shp->pwd = (char*)(PWDNOD->nvalue.cp);
nv_onattr(pwdnod,NV_NOFREE|NV_EXPORT);
/* Set shell PWD */
shp->pwd = (char*)(pwdnod->nvalue.cp);
return(cp);
}