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ws_pipe_spawn_*: fix deadlock in g_spawn on Linux with threads 

The deadlock can be observed with a slow malloc implementation, e.g.

    ASAN_OPTIONS=fast_unwind_on_malloc=0 tshark --version

(This calls extcap_run_all which uses threads and ws_pipe_spawn_sync.)

Change-Id: Iff329c465c53ed177980368cd645f59222f88dd3
Reviewed-on: https://code.wireshark.org/review/30777
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>
This commit is contained in:
Peter Wu 2018-11-24 15:20:22 +01:00 committed by Anders Broman
parent 9ae02a5918
commit 5e304f7718
1 changed files with 96 additions and 2 deletions
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98
wsutil/ws_pipe.c
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@ -30,9 +30,91 @@
#include <glib.h>
#include <log.h>
#ifdef __linux__
#define HAS_G_SPAWN_LINUX_THREAD_SAFETY_BUG
#include <fcntl.h>
#include <sys/syscall.h> /* for syscall and SYS_getdents64 */
#include <wsutil/file_util.h> /* for ws_open -> open to pacify checkAPIs.pl */
#endif
#include "wsutil/filesystem.h"
#include "wsutil/ws_pipe.h"
#ifdef HAS_G_SPAWN_LINUX_THREAD_SAFETY_BUG
struct linux_dirent64 {
guint64 d_ino; /* 64-bit inode number */
guint64 d_off; /* 64-bit offset to next structure */
unsigned short d_reclen; /* Size of this dirent */
unsigned char d_type; /* File type */
char d_name[]; /* Filename (null-terminated) */
};
/* Async-signal-safe string to integer conversion. */
static gint
filename_to_fd(const char *p)
{
char c;
int fd = 0;
const int cutoff = G_MAXINT / 10;
const int cutlim = G_MAXINT % 10;
if (*p == '\0')
return -1;
while ((c = *p++) != '\0') {
if (!g_ascii_isdigit(c))
return -1;
c -= '0';
/* Check for overflow. */
if (fd > cutoff || (fd == cutoff && c > cutlim))
return -1;
fd = fd * 10 + c;
}
return fd;
}
static void
close_non_standard_fds_linux(gpointer user_data _U_)
{
/*
* GLib 2.14.2 and newer (up to at least GLib 2.58.1) on Linux with multiple
* threads can deadlock in the child process due to use of opendir (which
* is not async-signal-safe). To avoid this, disable the broken code path
* and manually close file descriptors using async-signal-safe code only.
* Use CLOEXEC to allow reporting of execve errors to the parent via a pipe.
* https://gitlab.gnome.org/GNOME/glib/issues/1014
* https://gitlab.gnome.org/GNOME/glib/merge_requests/490
*/
int dir_fd = ws_open("/proc/self/fd", O_RDONLY | O_DIRECTORY);
if (dir_fd >= 0) {
char buf[4096];
int nread, fd;
struct linux_dirent64 *de;
while ((nread = (int) syscall(SYS_getdents64, dir_fd, buf, sizeof(buf))) > 0) {
for (int pos = 0; pos < nread; pos += de->d_reclen) {
de = (struct linux_dirent64 *)(buf + pos);
fd = filename_to_fd(de->d_name);
if (fd > STDERR_FILENO && fd != dir_fd) {
/* Close all other (valid) file descriptors above stderr. */
fcntl(fd, F_SETFD, FD_CLOEXEC);
}
}
}
close(dir_fd);
} else {
/* Slow fallback in case /proc is not mounted */
for (int fd = STDERR_FILENO + 1; fd < getdtablesize(); fd++) {
fcntl(fd, F_SETFD, FD_CLOEXEC);
}
}
}
#endif
gboolean ws_pipe_spawn_sync(const gchar *working_directory, const gchar *command, gint argc, gchar **args, gchar **command_output)
{
gboolean status = FALSE;
@ -212,8 +294,14 @@ gboolean ws_pipe_spawn_sync(const gchar *working_directory, const gchar *command
g_setenv("PATH", oldpath, TRUE);
#else
GSpawnFlags flags = (GSpawnFlags)0;
GSpawnChildSetupFunc child_setup = NULL;
#ifdef HAS_G_SPAWN_LINUX_THREAD_SAFETY_BUG
flags = (GSpawnFlags)(flags | G_SPAWN_LEAVE_DESCRIPTORS_OPEN);
child_setup = close_non_standard_fds_linux;
#endif
status = g_spawn_sync(working_directory, argv, NULL,
(GSpawnFlags) 0, NULL, NULL, &local_output, NULL, &exit_status, NULL);
flags, child_setup, NULL, &local_output, NULL, &exit_status, NULL);
if (status && exit_status != 0)
status = FALSE;
@ -346,8 +434,14 @@ GPid ws_pipe_spawn_async(ws_pipe_t *ws_pipe, GPtrArray *args)
g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_DEBUG, "async spawn params: %s", spawn_args->str);
GError *error = NULL;
GSpawnFlags flags = G_SPAWN_DO_NOT_REAP_CHILD;
GSpawnChildSetupFunc child_setup = NULL;
#ifdef HAS_G_SPAWN_LINUX_THREAD_SAFETY_BUG
flags = (GSpawnFlags)(flags | G_SPAWN_LEAVE_DESCRIPTORS_OPEN);
child_setup = close_non_standard_fds_linux;
#endif
gboolean spawned = g_spawn_async_with_pipes(NULL, (gchar **)args->pdata, NULL,
(GSpawnFlags) G_SPAWN_DO_NOT_REAP_CHILD, NULL, NULL,
flags, child_setup, NULL,
&pid, &ws_pipe->stdin_fd, &ws_pipe->stdout_fd, &ws_pipe->stderr_fd, &error);
if (!spawned) {
g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_DEBUG, "Error creating async pipe: %s", error->message);