Fix crash on 'exec' after 'unset SHLVL'
Resolves: RHEL-74970
This commit is contained in:
Vincent Mihalkovic
parent
bc7b8cb367
commit
23b9129ae9
139
ksh-1.0.11-SHLVL.patch
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139
ksh-1.0.11-SHLVL.patch
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@ -0,0 +1,139 @@
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From 7c945bdd6ba44bbb490504f44904ac65d705dd17 Mon Sep 17 00:00:00 2001
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From: Martijn Dekker <martijn@inlv.org>
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Date: Sun, 27 Oct 2024 01:34:38 +0000
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Subject: [PATCH] Fix crash on 'exec' after 'unset SHLVL' (re: fa0f9796)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Vincent Mihalkovič (@vmihalko) reports:
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> If the user unsets the SHLVL variable and later replaces the
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> shell by executing a command, ksh will segfault.
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>
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> Reproducer
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>
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> # unset -v SHLVL
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> # exec bash
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> Segmaentation fault (core dumped)
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>
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> Reason
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>
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> The reason for this is that the SHLVL variable is getting
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> decremented without any guard making sure it's still in the
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> environment, see:
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>
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> src/cmd/ksh93/bltins/misc.c:
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> 145: /* if the main shell is about to be replaced, decrease SHLVL
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> to cancel out a subsequent increase */
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> 146: if(!sh.realsubshell)
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> 147: (*SHLVL->nvalue.ip)--;
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This should be fixed so that SHLVL can be unset safely and lose its
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special properties like other special variables do.
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src/cmd/ksh93/sh/init.c,
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src/cmd/ksh93/include/shell.h:
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- Move the static 'shlvl' in init.c to the sh state struct, so that
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'sh.shlvl' can be accessed from the entire ksh93 code base.
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- Change its type from int to int32_t -- this is more correct as
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nv_getval() uses this type to retrieve the value. In practice,
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this makes no difference because sizeof(int) == sizeof(int32_t),
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but this is not guaranteed by the standards.
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src/cmd/ksh93/bltins/misc.c:
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- Access sh.shlvl directly instead of dereferencing the SHLVL value
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pointer, as this pointer is invalidated upon 'unset SHLVL'. This
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fixes the bug.
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Resolves: https://github.com/ksh93/ksh/issues/788
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---
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src/cmd/ksh93/bltins/misc.c | 2 +-
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src/cmd/ksh93/include/shell.h | 1 +
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src/cmd/ksh93/sh/init.c | 7 +++----
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src/cmd/ksh93/tests/variables.sh | 7 +++++++
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4 files changed, 12 insertions(+), 5 deletions(-)
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diff --git a/src/cmd/ksh93/bltins/misc.c b/src/cmd/ksh93/bltins/misc.c
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index cb7e883..1d49162 100644
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--- a/src/cmd/ksh93/bltins/misc.c
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+++ b/src/cmd/ksh93/bltins/misc.c
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@@ -144,7 +144,7 @@ int b_exec(int argc,char *argv[], Shbltin_t *context)
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return 1;
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/* if the main shell is about to be replaced, decrease SHLVL to cancel out a subsequent increase */
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if(!sh.realsubshell)
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- (*SHLVL->nvalue.ip)--;
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+ sh.shlvl--;
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sh_onstate(SH_EXEC);
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if(sh.subshell && !sh.subshare)
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{
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diff --git a/src/cmd/ksh93/include/shell.h b/src/cmd/ksh93/include/shell.h
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index c28b159..96d982a 100644
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--- a/src/cmd/ksh93/include/shell.h
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+++ b/src/cmd/ksh93/include/shell.h
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@@ -270,6 +270,7 @@ struct Shell_s
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* Programs using libshell should not rely on them as they may change. */
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int subshell; /* set for virtual subshell */
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int realsubshell; /* ${.sh.subshell}, actual subshell level (including virtual and forked) */
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+ int32_t shlvl; /* $SHLVL, non-subshell child shell level */
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char shcomp; /* set when running shcomp */
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unsigned char trapnote; /* set when trap/signal is pending */
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struct sh_scoped st; /* scoped information */
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diff --git a/src/cmd/ksh93/sh/init.c b/src/cmd/ksh93/sh/init.c
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index 1242789..1f1b71e 100644
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--- a/src/cmd/ksh93/sh/init.c
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+++ b/src/cmd/ksh93/sh/init.c
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@@ -220,7 +220,6 @@ static Init_t *nv_init(void);
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#if SHOPT_STATS
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static void stat_init(void);
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#endif
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-static int shlvl;
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static int rand_shift;
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/*
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@@ -1352,7 +1351,7 @@ Shell_t *sh_init(int argc,char *argv[], Shinit_f userinit)
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nv_putval(ENVNOD,sfstruse(sh.strbuf),NV_RDONLY);
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}
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/* increase SHLVL */
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- shlvl++;
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+ sh.shlvl++;
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#if SHOPT_SPAWN
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{
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/*
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@@ -1672,7 +1671,7 @@ void sh_reinit(void)
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else
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env_import_attributes(env_init());
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/* Increase SHLVL */
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- shlvl++;
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+ sh.shlvl++;
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/* call user init function, if any */
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if(sh.userinit)
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(*sh.userinit)(&sh, 1);
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@@ -1804,7 +1803,7 @@ static Init_t *nv_init(void)
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sh.nvfun.last = (char*)&sh;
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sh.nvfun.nofree = 1;
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sh.var_base = sh.var_tree = sh_inittree(shtab_variables);
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- SHLVL->nvalue.ip = &shlvl;
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+ SHLVL->nvalue.lp = &sh.shlvl;
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ip->IFS_init.hdr.disc = &IFS_disc;
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ip->PATH_init.disc = &RESTRICTED_disc;
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ip->PATH_init.nofree = 1;
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diff --git a/src/cmd/ksh93/tests/variables.sh b/src/cmd/ksh93/tests/variables.sh
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index 12a797a..5754085 100755
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--- a/src/cmd/ksh93/tests/variables.sh
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+++ b/src/cmd/ksh93/tests/variables.sh
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@@ -1619,5 +1619,12 @@ got=$(set +x; { "$SHELL" -c '
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"(expected status 0, $(printf %q "$exp");" \
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"got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"), $(printf %q "$got"))"
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+# ======
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+# exec after unset SHLVL
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+# https://github.com/ksh93/ksh/issues/788
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+{ "$SHELL" -c 'unset SHLVL; exec true'; } 2>/dev/null
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+(((e=$?)==0)) || err_exit "crash after unsetting SHLVL" \
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+ "(expected status 0, got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"))"
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+
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# ======
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exit $((Errors<125?Errors:125))
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--
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2.46.2
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9
ksh.spec
9
ksh.spec
@ -4,12 +4,15 @@ URL: http://www.kornshell.com/
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License: EPL-2.0
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Epoch: 3
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Version: 1.0.10
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Release: 2%{?dist}
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Release: 3%{?dist}
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Source0: https://github.com/ksh93/%{name}/archive/v%{version}/%{name}-%{version}.tar.gz
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Source1: kshcomp.conf
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Source2: kshrc.rhs
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Source3: dotkshrc
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#upstream commit: https://github.com/ksh93/ksh/commit/caae9aa23e2851cadf55f858a8f38b9f0de74314
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Patch1: ksh-1.0.11-SHLVL.patch
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Conflicts: pdksh
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Requires: coreutils, diffutils
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BuildRequires: gcc
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@ -138,6 +141,10 @@ fi
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%config(noreplace) %{_sysconfdir}/binfmt.d/kshcomp.conf
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%changelog
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* Mon Jan 13 2025 Vincent Mihalkovic <vmihalko@redhat.com> - 3:1.0.10-3
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- Fix crash on 'exec' after 'unset SHLVL'
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Resolves: RHEL-74970
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* Tue Oct 29 2024 Troy Dawson <tdawson@redhat.com> - 3:1.0.10-2
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- Bump release for October 2024 mass rebuild:
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Resolves: RHEL-64018
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