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path_pwd(): Fix use after free (re: 11177d44)

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Of course, we should not free the 'cp' pointer when we still need
to use it.

Resolves: https://github.com/ksh93/ksh/issues/467
Thanks to @atheik for the report.
This commit is contained in:
Martijn Dekker 2022-02-19 21:45:01 +01:00
parent f43bb4981f
commit bc6c5dbdd9
2 changed files with 13 additions and 4 deletions
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8
src/cmd/ksh93/sh/path.c
View file

@ -183,6 +183,7 @@ static pid_t command_xargs(const char *path, char *argv[],char *const envp[], in
char *path_pwd(void) char *path_pwd(void)
{ {
register char *cp; register char *cp;
char tofree = 0;
Namval_t *pwdnod; Namval_t *pwdnod;
/* Don't bother if PWD already set */ /* Don't bother if PWD already set */
if(sh.pwd) if(sh.pwd)
@ -198,7 +199,6 @@ char *path_pwd(void)
{ {
/* Check if $HOME is a path to the PWD; this ensures $PWD == $HOME /* Check if $HOME is a path to the PWD; this ensures $PWD == $HOME
at login, even if $HOME is a path that contains symlinks */ at login, even if $HOME is a path that contains symlinks */
char tofree = 0;
cp = nv_getval(sh_scoped(HOME)); cp = nv_getval(sh_scoped(HOME));
if(!(cp && *cp=='/' && test_inode(cp,e_dot))) if(!(cp && *cp=='/' && test_inode(cp,e_dot)))
{ {
@ -214,8 +214,6 @@ char *path_pwd(void)
pwdnod = sh_assignok(pwdnod,1); pwdnod = sh_assignok(pwdnod,1);
nv_putval(pwdnod,cp,NV_RDONLY); nv_putval(pwdnod,cp,NV_RDONLY);
} }
if(tofree)
free((void*)cp);
} }
nv_onattr(pwdnod,NV_EXPORT); nv_onattr(pwdnod,NV_EXPORT);
/* Neither obtained the pwd nor can fall back to sane-ish $PWD: fall back to "." */ /* Neither obtained the pwd nor can fall back to sane-ish $PWD: fall back to "." */
@ -224,7 +222,9 @@ char *path_pwd(void)
if(!cp || *cp!='/') if(!cp || *cp!='/')
nv_putval(pwdnod,cp=(char*)e_dot,NV_RDONLY); nv_putval(pwdnod,cp=(char*)e_dot,NV_RDONLY);
/* Set shell PWD */ /* Set shell PWD */
sh.pwd = sh_strdup(cp); if(!tofree)
cp = sh_strdup(cp);
sh.pwd = cp;
return((char*)sh.pwd); return((char*)sh.pwd);
} }

9
src/cmd/ksh93/tests/path.sh
View file

@ -944,6 +944,15 @@ cd "$tmp/testdir"
wait "$!" 2>/dev/null wait "$!" 2>/dev/null
((!(e = $?))) || err_exit 'shell crashes on failure obtain the PWD on init' \ ((!(e = $?))) || err_exit 'shell crashes on failure obtain the PWD on init' \
"(got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))" "(got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))"
cd "$tmp"
# ======
# https://github.com/ksh93/ksh/issues/467
[[ -d emptydir ]] || mkdir emptydir
got=$(unset PWD; "$SHELL" -c 'echo "$PWD"; pwd; cd emptydir' 2>&1)
exp=$PWD$'\n'$PWD
[[ $got == "$exp" ]] || err_exit "child shell failed to obtain PWD" \
"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
# ====== # ======
exit $((Errors<125?Errors:125)) exit $((Errors<125?Errors:125))