ash: eval: Reset handler when entering a subshell

Upstream commit:

    Date: Sun, 3 Mar 2019 21:57:50 +0800
    eval: Reset handler when entering a subshell

    As it is a subshell can execute code that is only meant for the
    parent shell when it executes a longjmp that is caught by something
    like evalcommand.  This patch fixes it by resetting the handler
    when entering a subshell.

function                                             old     new   delta
evalsubshell                                         169     183     +14
evalpipe                                             342     356     +14
argstr                                              1406    1416     +10
ash_main                                            1236    1226     -10
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/1 up/down: 65/-10)             Total: 28 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/shell/ash.c b/shell/ash.c
index a88fb804a..2c501993b 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -493,6 +493,8 @@ struct globals_misc {
 
         /* Rarely referenced stuff */
 
+        struct jmploc main_handler;
+
         /* Cached supplementary group array (for testing executable'ity of files) */
         struct cached_groupinfo groupinfo;
 
@@ -529,6 +531,7 @@ extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc;
 #define may_have_traps    (G_misc.may_have_traps   )
 #define trap        (G_misc.trap       )
 #define trap_ptr    (G_misc.trap_ptr   )
+#define main_handler      (G_misc.main_handler     )
 #define groupinfo   (G_misc.groupinfo  )
 #define random_gen  (G_misc.random_gen )
 #define backgndpid  (G_misc.backgndpid )
@@ -594,6 +597,14 @@ sigclearmask(void)
         sigprocmask_allsigs(SIG_UNBLOCK);
 }
 
+/* Reset handler when entering a subshell */
+static void
+reset_exception_handler(void)
+{
+        exception_handler = &main_handler;
+}
+
+
 /* ============ Parser data */
 
 /*
@@ -6720,6 +6731,7 @@ evalbackcmd(union node *n, struct backcmd *result
         jp = (ctl == CTLBACKQ) ? makejob(1) : NULL;
         if (forkshell(jp, n, FORK_NOJOB) == 0) {
                 /* child */
+                reset_exception_handler();
                 FORCEINTON;
                 close(pip[ip]);
                 /* ic is index of child end of pipe *and* fd to connect it to */
@@ -9705,6 +9717,7 @@ evalsubshell(union node *n, int flags)
                 if (backgnd)
                         flags &= ~EV_TESTED;
  nofork:
+                reset_exception_handler();
                 redirect(n->nredir.redirect, 0);
                 evaltreenr(n->nredir.n, flags);
                 /* never returns */
@@ -9817,6 +9830,7 @@ evalpipe(union node *n, int flags)
                 }
                 if (forkshell(jp, lp->n, n->npipe.pipe_backgnd) == 0) {
                         /* child */
+                        reset_exception_handler();
                         INTON;
                         if (pip[1] >= 0) {
                                 close(pip[0]);
@@ -14851,7 +14865,6 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
 /* note: 'argc' is used only if embedded scripts are enabled */
 {
         volatile smallint state;
-        struct jmploc jmploc;
         struct stackmark smark;
         int login_sh;
 
@@ -14869,7 +14882,7 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
 #endif
 
         state = 0;
-        if (setjmp(jmploc.loc)) {
+        if (setjmp(main_handler.loc)) {
                 smallint e;
                 smallint s;
 
@@ -14897,7 +14910,7 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
                         goto state3;
                 goto state4;
         }
-        exception_handler = &jmploc;
+        exception_handler = &main_handler;
         rootpid = getpid();
 
         init();