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process: Fix races on fatal signal handling in process_start().

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To prevent fatal signals in a child process from causing the parent
process's pidfile, etc. to be deleted, we need to block fatal signals
around fork and call fatal_signal_fork() in the child process.

This problem was noticed through code inspection; it has not been observed
in practice.
This commit is contained in:
Ben Pfaff
2009-07-15 12:05:04 -07:00
parent 8c4c1387fd
commit 52dc2ef41b
1 changed files with 7 additions and 0 deletions
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7
lib/process.c
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@@ -27,6 +27,7 @@
#include <unistd.h>
#include "coverage.h"
#include "dynamic-string.h"
#include "fatal-signal.h"
#include "list.h"
#include "poll-loop.h"
#include "socket-util.h"
@@ -51,6 +52,7 @@ static int fds[2];
/* All processes. */
static struct list all_processes = LIST_INITIALIZER(&all_processes);
static bool sigchld_is_blocked(void);
static void block_sigchld(sigset_t *);
static void unblock_sigchld(const sigset_t *);
static void sigchld_handler(int signr UNUSED);
@@ -158,8 +160,10 @@ process_start(char **argv,
free(binary);
block_sigchld(&oldsigs);
fatal_signal_block();
pid = fork();
if (pid < 0) {
fatal_signal_unblock();
unblock_sigchld(&oldsigs);
VLOG_WARN("fork failed: %s", strerror(errno));
return errno;
@@ -176,6 +180,7 @@ process_start(char **argv,
list_push_back(&all_processes, &p->node);
unblock_sigchld(&oldsigs);
fatal_signal_unblock();
*pp = p;
return 0;
@@ -184,6 +189,8 @@ process_start(char **argv,
int fd_max = get_max_fds();
int fd;
fatal_signal_fork();
fatal_signal_unblock();
unblock_sigchld(&oldsigs);
for (fd = 0; fd < fd_max; fd++) {
if (is_member(fd, null_fds, n_null_fds)) {