hush: fixes and small shrink for HUSH_JOB!=y

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

1 files changed, 17 insertions, 10 deletions

diff --git a/shell/hush.c b/shell/hush.c
index bb95d6318..132b974f0 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -805,9 +805,9 @@ struct globals {
         unsigned special_sig_mask;
 #if ENABLE_HUSH_JOB
         unsigned fatal_sig_mask;
-#define G_fatal_sig_mask G.fatal_sig_mask
+# define G_fatal_sig_mask G.fatal_sig_mask
 #else
-#define G_fatal_sig_mask 0
+# define G_fatal_sig_mask 0
 #endif
         char **traps; /* char *traps[NSIG] */
         sigset_t pending_set;
@@ -1414,6 +1414,9 @@ static void restore_G_args(save_arg_t *sv, char **argv)
  * Standard says "When a subshell is entered, traps that are not being ignored
  * are set to the default actions". bash interprets it so that traps which
  * are set to '' (ignore) are NOT reset to defaults. We do the same.
+ *
+ * TODO: don't use signal() to install sighandlers: need to mask ALL signals
+ * while handler runs. I saw signal nesting in one strace, race window isn't small.
  */
 enum {
         SPECIAL_INTERACTIVE_SIGS = 0
@@ -1486,12 +1489,13 @@ static sighandler_t pick_sighandler(unsigned sig)
                 unsigned sigmask = (1 << sig);
 
 #if ENABLE_HUSH_JOB
-                /* sig is fatal? */
+                /* is sig fatal? */
                 if (G_fatal_sig_mask & sigmask)
                         handler = sigexit;
+                else
 #endif
                 /* sig has special handling? */
-                else if (G.special_sig_mask & sigmask) {
+                if (G.special_sig_mask & sigmask) {
                         handler = record_pending_signo;
                         /* TTIN/TTOU/TSTP can't be set to record_pending_signo
                          * in order to ignore them: they will be raised
@@ -5604,9 +5608,6 @@ static void re_execute_shell(char ***to_free, const char *s,
          * _inside_ group (just before echo 1), it works.
          *
          * I conclude it means we don't need to pass active traps here.
-         * Even if we would use signal handlers instead of signal masking
-         * in order to implement trap handling,
-         * exec syscall below resets signals to SIG_DFL for us.
          */
         *pp++ = (char *) "-c";
         *pp++ = (char *) s;
@@ -5623,7 +5624,9 @@ static void re_execute_shell(char ***to_free, const char *s,
 
  do_exec:
         debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s);
-        switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
+        /* Don't propagate SIG_IGN to the child */
+        if (SPECIAL_JOBSTOP_SIGS != 0)
+                switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
         execve(bb_busybox_exec_path, argv, pp);
         /* Fallback. Useful for init=/bin/hush usage etc */
         if (argv[0][0] == '/')
@@ -6277,7 +6280,9 @@ static void execvp_or_die(char **argv) NORETURN;
 static void execvp_or_die(char **argv)
 {
         debug_printf_exec("execing '%s'\n", argv[0]);
-        switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
+        /* Don't propagate SIG_IGN to the child */
+        if (SPECIAL_JOBSTOP_SIGS != 0)
+                switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
         execvp(argv[0], argv);
         bb_perror_msg("can't execute '%s'", argv[0]);
         _exit(127); /* bash compat */
@@ -6409,7 +6414,9 @@ static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save,
 # endif
                         /* Re-exec ourselves */
                         debug_printf_exec("re-execing applet '%s'\n", argv[0]);
-                        switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
+                        /* Don't propagate SIG_IGN to the child */
+                        if (SPECIAL_JOBSTOP_SIGS != 0)
+                                switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
                         execv(bb_busybox_exec_path, argv);
                         /* If they called chroot or otherwise made the binary no longer
                          * executable, fall through */