From 23b9129ae975a3e6d5b72fa389567618a7c8025c Mon Sep 17 00:00:00 2001 From: Vincent Mihalkovic Date: Mon, 13 Jan 2025 13:25:40 +0100 Subject: [PATCH] Fix crash on 'exec' after 'unset SHLVL' Resolves: RHEL-74970 --- ksh-1.0.11-SHLVL.patch | 139 +++++++++++++++++++++++++++++++++++++++++ ksh.spec | 9 ++- 2 files changed, 147 insertions(+), 1 deletion(-) create mode 100644 ksh-1.0.11-SHLVL.patch diff --git a/ksh-1.0.11-SHLVL.patch b/ksh-1.0.11-SHLVL.patch new file mode 100644 index 0000000..b08c582 --- /dev/null +++ b/ksh-1.0.11-SHLVL.patch @@ -0,0 +1,139 @@ +From 7c945bdd6ba44bbb490504f44904ac65d705dd17 Mon Sep 17 00:00:00 2001 +From: Martijn Dekker +Date: Sun, 27 Oct 2024 01:34:38 +0000 +Subject: [PATCH] Fix crash on 'exec' after 'unset SHLVL' (re: fa0f9796) +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Vincent Mihalkovič (@vmihalko) reports: +> If the user unsets the SHLVL variable and later replaces the +> shell by executing a command, ksh will segfault. +> +> Reproducer +> +> # unset -v SHLVL +> # exec bash +> Segmaentation fault (core dumped) +> +> Reason +> +> The reason for this is that the SHLVL variable is getting +> decremented without any guard making sure it's still in the +> environment, see: +> +> src/cmd/ksh93/bltins/misc.c: +> 145: /* if the main shell is about to be replaced, decrease SHLVL +> to cancel out a subsequent increase */ +> 146: if(!sh.realsubshell) +> 147: (*SHLVL->nvalue.ip)--; + +This should be fixed so that SHLVL can be unset safely and lose its +special properties like other special variables do. + +src/cmd/ksh93/sh/init.c, +src/cmd/ksh93/include/shell.h: +- Move the static 'shlvl' in init.c to the sh state struct, so that + 'sh.shlvl' can be accessed from the entire ksh93 code base. +- Change its type from int to int32_t -- this is more correct as + nv_getval() uses this type to retrieve the value. In practice, + this makes no difference because sizeof(int) == sizeof(int32_t), + but this is not guaranteed by the standards. + +src/cmd/ksh93/bltins/misc.c: +- Access sh.shlvl directly instead of dereferencing the SHLVL value + pointer, as this pointer is invalidated upon 'unset SHLVL'. This + fixes the bug. + +Resolves: https://github.com/ksh93/ksh/issues/788 +--- + src/cmd/ksh93/bltins/misc.c | 2 +- + src/cmd/ksh93/include/shell.h | 1 + + src/cmd/ksh93/sh/init.c | 7 +++---- + src/cmd/ksh93/tests/variables.sh | 7 +++++++ + 4 files changed, 12 insertions(+), 5 deletions(-) + +diff --git a/src/cmd/ksh93/bltins/misc.c b/src/cmd/ksh93/bltins/misc.c +index cb7e883..1d49162 100644 +--- a/src/cmd/ksh93/bltins/misc.c ++++ b/src/cmd/ksh93/bltins/misc.c +@@ -144,7 +144,7 @@ int b_exec(int argc,char *argv[], Shbltin_t *context) + return 1; + /* if the main shell is about to be replaced, decrease SHLVL to cancel out a subsequent increase */ + if(!sh.realsubshell) +- (*SHLVL->nvalue.ip)--; ++ sh.shlvl--; + sh_onstate(SH_EXEC); + if(sh.subshell && !sh.subshare) + { +diff --git a/src/cmd/ksh93/include/shell.h b/src/cmd/ksh93/include/shell.h +index c28b159..96d982a 100644 +--- a/src/cmd/ksh93/include/shell.h ++++ b/src/cmd/ksh93/include/shell.h +@@ -270,6 +270,7 @@ struct Shell_s + * Programs using libshell should not rely on them as they may change. */ + int subshell; /* set for virtual subshell */ + int realsubshell; /* ${.sh.subshell}, actual subshell level (including virtual and forked) */ ++ int32_t shlvl; /* $SHLVL, non-subshell child shell level */ + char shcomp; /* set when running shcomp */ + unsigned char trapnote; /* set when trap/signal is pending */ + struct sh_scoped st; /* scoped information */ +diff --git a/src/cmd/ksh93/sh/init.c b/src/cmd/ksh93/sh/init.c +index 1242789..1f1b71e 100644 +--- a/src/cmd/ksh93/sh/init.c ++++ b/src/cmd/ksh93/sh/init.c +@@ -220,7 +220,6 @@ static Init_t *nv_init(void); + #if SHOPT_STATS + static void stat_init(void); + #endif +-static int shlvl; + static int rand_shift; + + /* +@@ -1352,7 +1351,7 @@ Shell_t *sh_init(int argc,char *argv[], Shinit_f userinit) + nv_putval(ENVNOD,sfstruse(sh.strbuf),NV_RDONLY); + } + /* increase SHLVL */ +- shlvl++; ++ sh.shlvl++; + #if SHOPT_SPAWN + { + /* +@@ -1672,7 +1671,7 @@ void sh_reinit(void) + else + env_import_attributes(env_init()); + /* Increase SHLVL */ +- shlvl++; ++ sh.shlvl++; + /* call user init function, if any */ + if(sh.userinit) + (*sh.userinit)(&sh, 1); +@@ -1804,7 +1803,7 @@ static Init_t *nv_init(void) + sh.nvfun.last = (char*)&sh; + sh.nvfun.nofree = 1; + sh.var_base = sh.var_tree = sh_inittree(shtab_variables); +- SHLVL->nvalue.ip = &shlvl; ++ SHLVL->nvalue.lp = &sh.shlvl; + ip->IFS_init.hdr.disc = &IFS_disc; + ip->PATH_init.disc = &RESTRICTED_disc; + ip->PATH_init.nofree = 1; +diff --git a/src/cmd/ksh93/tests/variables.sh b/src/cmd/ksh93/tests/variables.sh +index 12a797a..5754085 100755 +--- a/src/cmd/ksh93/tests/variables.sh ++++ b/src/cmd/ksh93/tests/variables.sh +@@ -1619,5 +1619,12 @@ got=$(set +x; { "$SHELL" -c ' + "(expected status 0, $(printf %q "$exp");" \ + "got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"), $(printf %q "$got"))" + ++# ====== ++# exec after unset SHLVL ++# https://github.com/ksh93/ksh/issues/788 ++{ "$SHELL" -c 'unset SHLVL; exec true'; } 2>/dev/null ++(((e=$?)==0)) || err_exit "crash after unsetting SHLVL" \ ++ "(expected status 0, got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))" ++ + # ====== + exit $((Errors<125?Errors:125)) +-- +2.46.2 + diff --git a/ksh.spec b/ksh.spec index 01e8f80..837d31b 100644 --- a/ksh.spec +++ b/ksh.spec @@ -4,12 +4,15 @@ URL: http://www.kornshell.com/ License: EPL-2.0 Epoch: 3 Version: 1.0.10 -Release: 2%{?dist} +Release: 3%{?dist} Source0: https://github.com/ksh93/%{name}/archive/v%{version}/%{name}-%{version}.tar.gz Source1: kshcomp.conf Source2: kshrc.rhs Source3: dotkshrc +#upstream commit: https://github.com/ksh93/ksh/commit/caae9aa23e2851cadf55f858a8f38b9f0de74314 +Patch1: ksh-1.0.11-SHLVL.patch + Conflicts: pdksh Requires: coreutils, diffutils BuildRequires: gcc @@ -138,6 +141,10 @@ fi %config(noreplace) %{_sysconfdir}/binfmt.d/kshcomp.conf %changelog +* Mon Jan 13 2025 Vincent Mihalkovic - 3:1.0.10-3 +- Fix crash on 'exec' after 'unset SHLVL' + Resolves: RHEL-74970 + * Tue Oct 29 2024 Troy Dawson - 3:1.0.10-2 - Bump release for October 2024 mass rebuild: Resolves: RHEL-64018