From 423cfa40efe859448b69fbbbce62a5be750bc9fd Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Mon, 13 May 2024 13:11:58 -0400
Subject: xspawn: Mask signals before fork()
This prevents signal handlers from running in the child before execve().
---
src/xspawn.c | 37 +++++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 8 deletions(-)
diff --git a/src/xspawn.c b/src/xspawn.c
index 0b0cea4..5a8277d 100644
--- a/src/xspawn.c
+++ b/src/xspawn.c
@@ -5,9 +5,11 @@
#include "xspawn.h"
#include "alloc.h"
#include "bfstd.h"
+#include "diag.h"
#include "list.h"
#include <errno.h>
#include <fcntl.h>
+#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
@@ -590,30 +592,49 @@ static pid_t bfs_fork_spawn(struct bfs_resolver *res, const struct bfs_spawn *ct
return -1;
}
+ // Block signals before fork() so handlers don't run in the child
+ sigset_t new_mask;
+ if (sigfillset(&new_mask) != 0) {
+ goto fail;
+ }
+ sigset_t old_mask;
+ errno = pthread_sigmask(SIG_BLOCK, &new_mask, &old_mask);
+ if (errno != 0) {
+ goto fail;
+ }
+
pid_t pid = fork();
- if (pid < 0) {
- close_quietly(pipefd[1]);
- close_quietly(pipefd[0]);
- return -1;
- } else if (pid == 0) {
+ if (pid == 0) {
// Child
bfs_spawn_exec(res, ctx, argv, envp, pipefd);
}
- // Parent
+ // Restore the original signal mask
+ int ret = pthread_sigmask(SIG_SETMASK, &old_mask, NULL);
+ bfs_verify(ret == 0, "pthread_sigmask(): %s", xstrerror(ret));
+
+ if (pid < 0) {
+ // fork() failed
+ goto fail;
+ }
+
xclose(pipefd[1]);
int error;
ssize_t nbytes = xread(pipefd[0], &error, sizeof(error));
xclose(pipefd[0]);
if (nbytes == sizeof(error)) {
- int wstatus;
- xwaitpid(pid, &wstatus, 0);
+ xwaitpid(pid, NULL, 0);
errno = error;
return -1;
}
return pid;
+
+fail:
+ close_quietly(pipefd[1]);
+ close_quietly(pipefd[0]);
+ return -1;
}
/** Call the right bfs_spawn() implementation. */
--
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