hush: use SA_RESTARTed signal handlers across read.

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

2 files changed, 42 insertions, 29 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 71972f751..509bd415b 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -792,8 +792,13 @@ struct globals {
         unsigned handled_SIGCHLD;
         smallint we_have_children;
 #endif
-        /* which signals have non-DFL handler (even with no traps set)? */
-        unsigned non_DFL_mask;
+        /* Which signals have non-DFL handler (even with no traps set)?
+         * Set at the start to:
+         * (SIGQUIT + maybe SPECIAL_INTERACTIVE_SIGS + maybe SPECIAL_JOB_SIGS)
+         * SPECIAL_INTERACTIVE_SIGS are cleared after fork.
+         * Other than these two times, never modified.
+         */
+        unsigned special_sig_mask;
         char **traps; /* char *traps[NSIG] */
         /* Signal mask on the entry to the (top-level) shell. Never modified. */
         sigset_t inherited_set;
@@ -1341,11 +1346,11 @@ static void restore_G_args(save_arg_t *sv, char **argv)
  * After each pipe execution, we extract any pending signals via sigtimedwait()
  * and act on them.
  *
- * unsigned non_DFL_mask: a mask of such "special" signals
+ * unsigned special_sig_mask: a mask of such "special" signals
  * sigset_t blocked_set:  current blocked signal set
  *
  * "trap - SIGxxx":
- *    clear bit in blocked_set unless it is also in non_DFL_mask
+ *    clear bit in blocked_set unless it is also in special_sig_mask
  * "trap 'cmd' SIGxxx":
  *    set bit in blocked_set (even if 'cmd' is '')
  * after [v]fork, if we plan to be a shell:
@@ -5376,7 +5381,7 @@ static void reset_traps_to_defaults(void)
          * Testcase: (while :; do :; done) + ^Z should background.
          * Same goes for SIGTERM, SIGHUP, SIGINT.
          */
-        if (!G.traps && !(G.non_DFL_mask & SPECIAL_INTERACTIVE_SIGS))
+        if (!G.traps && !(G.special_sig_mask & SPECIAL_INTERACTIVE_SIGS))
                 return; /* already no traps and no SPECIAL_INTERACTIVE_SIGS */
 
         /* Switching off SPECIAL_INTERACTIVE_SIGS.
@@ -5394,10 +5399,10 @@ static void reset_traps_to_defaults(void)
                 }
         }
         /* Our homegrown sig mask is saner to work with :) */
-        G.non_DFL_mask &= ~SPECIAL_INTERACTIVE_SIGS;
+        G.special_sig_mask &= ~SPECIAL_INTERACTIVE_SIGS;
 
         /* Resetting all traps to default except empty ones */
-        mask = G.non_DFL_mask;
+        mask = G.special_sig_mask;
         if (G.traps) for (sig = 0; sig < NSIG; sig++, mask >>= 1) {
                 if (!G.traps[sig] || !G.traps[sig][0])
                         continue;
@@ -7440,9 +7445,6 @@ static void init_sigmasks(void)
 
         /* POSIX allows shell to re-enable SIGCHLD
          * even if it was SIG_IGN on entry */
-#if ENABLE_HUSH_FAST
-        G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
-#endif
         if (!G.inherited_set_is_saved) {
 #if ENABLE_HUSH_FAST
                 signal(SIGCHLD, SIGCHLD_handler);
@@ -7460,7 +7462,7 @@ static void init_sigmasks(void)
                 if (G_saved_tty_pgrp) /* we have ctty, job control sigs work */
                         mask |= SPECIAL_JOB_SIGS;
         }
-        G.non_DFL_mask = mask;
+        G.special_sig_mask = mask;
 
         /* Block them. And unblock SIGCHLD */
         sig = 0;
@@ -7504,10 +7506,10 @@ static void set_fatal_handlers_to_sigexit(void)
                 /*+ (1 << SIGINT )*/
         ;
 
-        /* non_DFL_mask'ed signals are, well, masked,
+        /* special_sig_mask'ed signals are, well, masked,
          * no need to set handler for them.
          */
-        fatal_sigs &= ~G.non_DFL_mask;
+        fatal_sigs &= ~G.special_sig_mask;
 
         /* For each sig in fatal_sigs... */
         sig = 0;
@@ -7571,8 +7573,11 @@ int hush_main(int argc, char **argv)
         struct variable *shell_ver;
 
         INIT_G();
-        if (EXIT_SUCCESS) /* if EXIT_SUCCESS == 0, it is already done */
+        if (EXIT_SUCCESS != 0) /* if EXIT_SUCCESS == 0, it is already done */
                 G.last_exitcode = EXIT_SUCCESS;
+#if ENABLE_HUSH_FAST
+        G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
+#endif
 #if !BB_MMU
         G.argv0_for_re_execing = argv[0];
 #endif
@@ -8303,7 +8308,7 @@ static int FAST_FUNC builtin_trap(char **argv)
                                 /* There was a trap handler, we are removing it
                                  * (if sig has non-DFL handling,
                                  * we don't need to do anything) */
-                                if (sig < 32 && (G.non_DFL_mask & (1 << sig)))
+                                if (sig < sizeof(G.special_sig_mask)*8 && (G.special_sig_mask & (1 << sig)))
                                         continue;
                                 sigdelset(&G.blocked_set, sig);
                         }
@@ -8565,7 +8570,7 @@ static int FAST_FUNC builtin_read(char **argv)
 
                 memset(&sa, 0, sizeof(sa));
                 sigfillset(&sa.sa_mask);
-                /*sa.sa_flags = 0;*/
+                sa.sa_flags = SA_RESTART;
                 sa.sa_handler = record_signal;
 
                 sig = 0;
diff --git a/shell/shell_common.c b/shell/shell_common.c
index a5c455c8e..bbc22ed34 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -159,32 +159,40 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
         bufpos = 0;
         do {
                 char c;
+                struct pollfd pfd[1];
+                int timeout;
 
-                errno = 0;
+                if ((bufpos & 0xff) == 0)
+                        buffer = xrealloc(buffer, bufpos + 0x100);
 
+                timeout = -1;
                 if (end_ms) {
-                        int timeout;
-                        struct pollfd pfd[1];
-
-                        pfd[0].fd = fd;
-                        pfd[0].events = POLLIN;
                         timeout = end_ms - (unsigned)monotonic_ms();
-                        if (timeout <= 0 /* already late? */
-                         || poll(pfd, 1, timeout) != 1 /* no? wait... */
-                        ) { /* timed out! */
-                                err = errno;
+                        if (timeout <= 0) { /* already late? */
                                 retval = (const char *)(uintptr_t)1;
                                 goto ret;
                         }
                 }
 
-                if ((bufpos & 0xff) == 0)
-                        buffer = xrealloc(buffer, bufpos + 0x100);
-                if (nonblock_immune_read(fd, &buffer[bufpos], 1, /*loop_on_EINTR:*/ 0) != 1) {
+                /* We must poll even if timeout is -1:
+                 * we want to be interrupted if signal arrives,
+                 * regardless of SA_RESTART-ness of that signal!
+                 */
+                errno = 0;
+                pfd[0].fd = fd;
+                pfd[0].events = POLLIN;
+                if (poll(pfd, 1, timeout) != 1) {
+                        /* timed out, or EINTR */
+                        err = errno;
+                        retval = (const char *)(uintptr_t)1;
+                        goto ret;
+                }
+                if (read(fd, &buffer[bufpos], 1) != 1) {
                         err = errno;
                         retval = (const char *)(uintptr_t)1;
                         break;
                 }
+
                 c = buffer[bufpos];
                 if (c == '\0')
                         continue;