hush: plug the leak on NOMMU re-execute path

function                                             old     new   delta
clean_up_after_re_execute                              -      58     +58
re_execute_shell                                     226     244     +18
run_pipe                                            1271    1276      +5
generate_stream_from_string                          133     138      +5
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/0 up/down: 86/0)               Total: 86 bytes

1 files changed, 32 insertions, 3 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 8ffdfb1a8..47eff0fb8 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -481,11 +481,14 @@ struct globals {
         smallint fake_mode;
         /* These four support $?, $#, and $1 */
         smalluint last_return_code;
-        /* is global_argv and global_argv[1..n] malloced? (note: not [0]) */
+        /* are global_argv and global_argv[1..n] malloced? (note: not [0]) */
         smalluint global_args_malloced;
         /* how many non-NULL argv's we have. NB: $# + 1 */
         int global_argc;
         char **global_argv;
+#if !BB_MMU
+        char **argv_for_re_execing;
+#endif
 #if ENABLE_HUSH_LOOPS
         unsigned depth_break_continue;
         unsigned depth_of_loop;
@@ -1127,7 +1130,9 @@ static int set_local_var(char *str, int flg_export, int flg_read_only)
 
  set_str_and_exp:
         cur->varstr = str;
+#if !BB_MMU
         cur->flg_read_only = flg_read_only;
+#endif
  exp:
         if (flg_export == 1)
                 cur->flg_export = 1;
@@ -2338,6 +2343,7 @@ static void pseudo_exec_argv(nommu_save_t *nommu_save,
         _exit(EXIT_FAILURE);
 }
 
+#if !BB_MMU
 static void re_execute_shell(const char *s) NORETURN;
 static void re_execute_shell(const char *s)
 {
@@ -2354,7 +2360,7 @@ static void re_execute_shell(const char *s)
                         cnt += 2;
         }
 //TODO: need to free these strings in parent!
-        argv = pp = xmalloc(sizeof(argv[0]) * cnt);
+        G.argv_for_re_execing = pp = xmalloc(sizeof(argv[0]) * cnt);
         *pp++ = (char *) applet_name;
         *pp++ = xasprintf("-$%u", G.root_pid);
         *pp++ = xasprintf("-?%u", G.last_return_code);
@@ -2379,11 +2385,28 @@ static void re_execute_shell(const char *s)
 //TODO: pass traps and functions
 
         debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s);
-        execv(bb_busybox_exec_path, argv);
+        sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
+        execv(bb_busybox_exec_path, G.argv_for_re_execing);
 //TODO: fallback for init=/bin/hush?
         _exit(127);
 }
 
+static void clean_up_after_re_execute(void)
+{
+        char **pp = G.argv_for_re_execing;
+        if (pp) {
+                /* Must match re_execute_shell's allocations */
+                free(pp[1]);
+                free(pp[2]);
+                free(pp[3]);
+                free(pp);
+                G.argv_for_re_execing = NULL;
+        }
+}
+#else
+#define clean_up_after_re_execute() ((void)0)
+#endif
+
 static int run_list(struct pipe *pi);
 
 /* Called after [v]fork() in run_pipe()
@@ -2892,9 +2915,11 @@ static int run_pipe(struct pipe *pi)
                         pseudo_exec((nommu_save_t*) &nommu_save, command, argv_expanded);
                         /* pseudo_exec() does not return */
                 }
+
                 /* parent */
 #if !BB_MMU
                 /* Clean up after vforked child */
+                clean_up_after_re_execute();
                 free(nommu_save.argv);
                 free_strings_and_unsetenv(nommu_save.new_env, 1);
                 putenv_all(nommu_save.old_env);
@@ -3890,6 +3915,7 @@ static FILE *generate_stream_from_string(const char *s)
         }
 
         /* parent */
+        clean_up_after_re_execute();
         close(channel[1]);
         pf = fdopen(channel[0], "r");
         return pf;
@@ -4827,6 +4853,9 @@ static struct pipe *parse_stream(char **pstring,
                  * while if false; then false; fi do break; done
                  * (bash accepts it)
                  * while if false; then false; fi; do break; fi
+                 * Samples to catch leaks at execution:
+                 * while if (true | {true;}); then echo ok; fi; do break; done
+                 * while if (true | {true;}); then echo ok; fi; do (if echo ok; break; then :; fi) | cat; break; done
                  */
                 pctx = &ctx;
                 do {