jiangcuo/node
1
0
Fork 0
mirror of https://github.com/nodejs/node.git synced 2025-05-08 20:39:30 +00:00
Code Issues Actions 12 Packages Projects Releases Wiki Activity

uv: cherry-pick libuv commit 041d60e into node

Browse Source 
Fixes execve-after-fork race in uv_spawn().
This commit is contained in:
Ben Noordhuis 2011-08-05 04:27:18 +02:00
parent 5a49522ba7
commit 2fe4558c10
1 changed files with 71 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

75
deps/uv/src/uv-unix.c vendored
View File

@ -42,6 +42,14 @@
#include <arpa/inet.h>
#include <limits.h> /* PATH_MAX */
#include <sys/uio.h> /* writev */
#include <poll.h>
#ifdef __linux__
#include <linux/version.h>
/* pipe2() requires linux >= 2.6.27 and glibc >= 2.9 */
#define HAVE_PIPE2 \
defined(LINUX_VERSION_CODE) && defined(__GLIBC_PREREQ) && LINUX_VERSION_CODE >= 0x2061B && __GLIBC_PREREQ(2, 9))
#endif
#ifdef __sun
# include <sys/types.h>
@ -2218,6 +2226,9 @@ int uv_spawn(uv_process_t* process, uv_process_options_t options) {
int stdin_pipe[2] = { -1, -1 };
int stdout_pipe[2] = { -1, -1 };
int stderr_pipe[2] = { -1, -1 };
int signal_pipe[2] = { -1, -1 };
struct pollfd pfd;
int status;
pid_t pid;
uv__handle_init((uv_handle_t*)process, UV_PROCESS);
@ -2258,8 +2269,49 @@ int uv_spawn(uv_process_t* process, uv_process_options_t options) {
}
}
/* This pipe is used by the parent to wait until
* the child has called `execve()`. We need this
* to avoid the following race condition:
*
* if ((pid = fork()) > 0) {
* kill(pid, SIGTERM);
* }
* else if (pid == 0) {
* execve("/bin/cat", argp, envp);
* }
*
* The parent sends a signal immediately after forking.
* Since the child may not have called `execve()` yet,
* there is no telling what process receives the signal,
* our fork or /bin/cat.
*
* To avoid ambiguity, we create a pipe with both ends
* marked close-on-exec. Then, after the call to `fork()`,
* the parent polls the read end until it sees POLLHUP.
*/
#ifdef HAVE_PIPE2
if (pipe2(signal_pipe, O_CLOEXEC | O_NONBLOCK) < 0) {
goto error;
}
#else
if (pipe(signal_pipe) < 0) {
goto error;
}
uv__cloexec(signal_pipe[0]);
uv__cloexec(signal_pipe[1]);
uv__nonblock(signal_pipe[0]);
uv__nonblock(signal_pipe[1]);
#endif
pid = fork();
if (pid == -1) {
uv__close(signal_pipe[0]);
uv__close(signal_pipe[1]);
environ = save_our_env;
goto error;
}
if (pid == 0) {
if (stdin_pipe[0] >= 0) {
uv__close(stdin_pipe[1]);
@ -2287,10 +2339,6 @@ int uv_spawn(uv_process_t* process, uv_process_options_t options) {
perror("execvp()");
_exit(127);
/* Execution never reaches here. */
} else if (pid == -1) {
/* Restore environment. */
environ = save_our_env;
goto error;
}
/* Parent. */
@ -2298,6 +2346,25 @@ int uv_spawn(uv_process_t* process, uv_process_options_t options) {
/* Restore environment. */
environ = save_our_env;
/* POLLHUP signals child has exited or execve()'d. */
uv__close(signal_pipe[1]);
do {
pfd.fd = signal_pipe[0];
pfd.events = POLLIN|POLLHUP;
pfd.revents = 0;
errno = 0, status = poll(&pfd, 1, -1);
}
while (status == -1 && (errno == EINTR || errno == ENOMEM));
uv__close(signal_pipe[0]);
assert((status == 1)
&& "poll() on pipe read end failed");
assert((pfd.revents & POLLIN) == 0
&& "unexpected POLLIN on pipe read end");
assert((pfd.revents & POLLHUP) == POLLHUP
&& "no POLLHUP on pipe read end");
process->pid = pid;
ev_child_init(&process->child_watcher, uv__chld, pid, 0);