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https://github.com/clearlinux/graphene.git
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b525fd8e62
Previously, Graphene forgot to reset signal handlers to defaults. This led to segfaults when parent process installed a signal handler (e.g., SIGCHLD), spawned a child via execve(), and the child spawned a grand-child via e.g. fork(). When the grand-child terminated, the child noticed that it had some SIGCHLD handler installed and tried to call it, but the memory region where the handler was in parent didn't exist any more, so Graphene crashed with segfault. This commit resets signal handlers on execve() to fix this bug. New LibOS test is added. Kudos to Manoj Gopalakrishnan for reporting this bug.
63 lines
1.7 KiB
C
63 lines
1.7 KiB
C
#define _XOPEN_SOURCE 700
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#include <errno.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/wait.h>
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#include <unistd.h>
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static void child_handler(int sig) {
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(void)sig;
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/* should never be printed because child doesn't inherit this handler */
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printf("Handled SIGCHLD\n");
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fflush(stdout);
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}
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int main(int argc, const char** argv, const char** envp) {
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if (argc > 1) {
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/* execv'ed child: do dummy fork, wait, and exit */
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pid_t child_pid = fork();
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if (child_pid == 0) {
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/* child just exits */
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return 0;
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} else if (child_pid > 0) {
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/* parent waits for child termination */
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int status;
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pid_t pid = wait(&status);
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if (pid != child_pid) {
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perror("wait failed");
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return 1;
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}
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if (WIFEXITED(status))
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printf("child exited with status: %d\n", WEXITSTATUS(status));
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} else {
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/* error */
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perror("fork failed");
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return 1;
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}
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puts("test completed successfully");
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return 0;
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}
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/* set signal handler for SIGCHLD signal */
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struct sigaction sa = {0};
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sa.sa_handler = child_handler;
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int ret = sigaction(SIGCHLD, &sa, NULL);
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if (ret < 0) {
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perror("sigaction error");
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return 1;
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}
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printf("Set up handler for SIGCHLD\n");
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fflush(stdout);
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/* SIGCHLD signal handler must *not* be inherited by execv'ed child */
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char* const new_argv[] = {(char*)argv[0], "dummy", NULL};
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execv(new_argv[0], new_argv);
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perror("execv failed");
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return 1;
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}
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