0806e401d
Denys Vlasenko
2011-05-12
Subject
hush: install signal handlers with filled sigmask
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shell/hush.c+28 -9
| @@ -815,6 +815,7 @@ struct globals { | |
| unsigned long memleak_value; | |
| int debug_indent; | |
| #endif | |
| + | struct sigaction sa; |
| char user_input_buf[ENABLE_FEATURE_EDITING ? CONFIG_FEATURE_EDITING_MAX_LEN : 2]; | |
| }; | |
| #define G (*ptr_to_globals) | |
| @@ -823,6 +824,9 @@ struct globals { | |
| * is global, thus "G." prefix is a useful hint */ | |
| #define INIT_G() do { \ | |
| SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \ | |
| + | /* memset(&G.sa, 0, sizeof(G.sa)); */ \ |
| + | sigfillset(&G.sa.sa_mask); \ |
| + | G.sa.sa_flags = SA_RESTART; \ |
| } while (0) | |
| @@ -1414,9 +1418,6 @@ 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 | |
| @@ -1444,6 +1445,24 @@ static void record_pending_signo(int sig) | |
| #endif | |
| } | |
| + | static sighandler_t install_sighandler(int sig, sighandler_t handler) |
| + | { |
| + | struct sigaction old_sa; |
| + | |
| + | /* We could use signal() to install handlers... almost: |
| + | * except that we need to mask ALL signals while handlers run. |
| + | * I saw signal nesting in strace, race window isn't small. |
| + | * SA_RESTART is also needed, but in Linux, signal() |
| + | * sets SA_RESTART too. |
| + | */ |
| + | /* memset(&G.sa, 0, sizeof(G.sa)); - already done */ |
| + | /* sigfillset(&G.sa.sa_mask); - already done */ |
| + | /* G.sa.sa_flags = SA_RESTART; - already done */ |
| + | G.sa.sa_handler = handler; |
| + | sigaction(sig, &G.sa, &old_sa); |
| + | return old_sa.sa_handler; |
| + | } |
| + | |
| #if ENABLE_HUSH_JOB | |
| /* After [v]fork, in child: do not restore tty pgrp on xfunc death */ | |
| @@ -5451,7 +5470,7 @@ static void switch_off_special_sigs(unsigned mask) | |
| G.traps[sig] = NULL; | |
| } | |
| /* We are here only if no trap or trap was not '' */ | |
| - | signal(sig, SIG_DFL); |
| + | install_sighandler(sig, SIG_DFL); |
| } | |
| } | |
| @@ -5496,7 +5515,7 @@ static void reset_traps_to_defaults(void) | |
| /* There is no signal for trap 0 (EXIT) */ | |
| if (sig == 0) | |
| continue; | |
| - | signal(sig, pick_sighandler(sig)); |
| + | install_sighandler(sig, pick_sighandler(sig)); |
| } | |
| } | |
| @@ -7524,7 +7543,7 @@ static void install_sighandlers(unsigned mask) | |
| sig++; | |
| if (!(mask & 1)) | |
| continue; | |
| - | old_handler = signal(sig, pick_sighandler(sig)); |
| + | old_handler = install_sighandler(sig, pick_sighandler(sig)); |
| /* POSIX allows shell to re-enable SIGCHLD | |
| * even if it was SIG_IGN on entry. | |
| * Therefore we skip IGN check for it: | |
| @@ -7533,7 +7552,7 @@ static void install_sighandlers(unsigned mask) | |
| continue; | |
| if (old_handler == SIG_IGN) { | |
| /* oops... restore back to IGN, and record this fact */ | |
| - | signal(sig, old_handler); |
| + | install_sighandler(sig, old_handler); |
| if (!G.traps) | |
| G.traps = xzalloc(sizeof(G.traps[0]) * NSIG); | |
| free(G.traps[sig]); | |
| @@ -7854,7 +7873,7 @@ int hush_main(int argc, char **argv) | |
| for (sig = 1; sig < NSIG; sig++) { | |
| if (empty_trap_mask & (1LL << sig)) { | |
| G.traps[sig] = xzalloc(1); /* == xstrdup(""); */ | |
| - | signal(sig, SIG_IGN); |
| + | install_sighandler(sig, SIG_IGN); |
| } | |
| } | |
| } | |
| @@ -8389,7 +8408,7 @@ static int FAST_FUNC builtin_trap(char **argv) | |
| else | |
| /* We are removing trap handler */ | |
| handler = pick_sighandler(sig); | |
| - | signal(sig, handler); |
| + | install_sighandler(sig, handler); |
| } | |
| return ret; | |
| } | |