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res_agi.c: Ensure SIGCHLD handler functions are properly balanced.

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Calls to `ast_replace_sigchld()` and `ast_unreplace_sigchld()` must be
balanced to ensure that we can capture the exit status of child
processes when we need to. This extends to functions that call
`ast_replace_sigchld()` and `ast_unreplace_sigchld()` such as
`ast_safe_fork()` and `ast_safe_fork_cleanup()`.

The primary change here is ensuring that we do not call
`ast_safe_fork_cleanup()` in `res_agi.c` if we have not previously
called `ast_safe_fork()`.

Additionally we reinforce some of the documentation and add an
assertion to, ideally, catch this sooner were this to happen again.

Fixes #922

(cherry picked from commit e1f2866bb6)
This commit is contained in:
Sean Bright
2024-09-30 11:48:56 -04:00
committed by Asterisk Development Team
parent ab79321a29
commit 682ad186fb
4 changed files with 19 additions and 5 deletions
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2
apps/app_voicemail.c
View File

@@ -15803,7 +15803,6 @@ AST_TEST_DEFINE(test_voicemail_msgcount)
if (!(vmu = find_user(&svm, testcontext, testmailbox)) &&
!(vmu = find_or_create(testcontext, testmailbox))) {
ast_test_status_update(test, "Cannot create vmu structure\n");
ast_unreplace_sigchld();
#ifdef IMAP_STORAGE
chan = ast_channel_unref(chan);
#endif
@@ -15825,7 +15824,6 @@ AST_TEST_DEFINE(test_voicemail_msgcount)
if ((syserr = ast_safe_system(syscmd))) {
ast_test_status_update(test, "Unable to create test voicemail: %s\n",
syserr > 0 ? strerror(syserr) : "unable to fork()");
ast_unreplace_sigchld();
#ifdef IMAP_STORAGE
chan = ast_channel_unref(chan);
#endif

4
include/asterisk/app.h
View File

@@ -1491,6 +1491,10 @@ int ast_safe_fork(int stop_reaper);
/*!
* \brief Common routine to cleanup after fork'ed process is complete (if reaping was stopped)
*
* \note This must <b>not</b> be called unless ast_safe_fork(1) has been called
* previously.
*
* \since 1.6.1
*/
void ast_safe_fork_cleanup(void);

4
main/asterisk.c
View File

@@ -1118,6 +1118,10 @@ void ast_unreplace_sigchld(void)
unsigned int level;
ast_mutex_lock(&safe_system_lock);
/* Wrapping around here is an error */
ast_assert(safe_system_level > 0);
level = --safe_system_level;
/* only restore the handler if we are the last one */

12
res/res_agi.c
View File

@@ -2192,12 +2192,15 @@ static enum agi_result launch_ha_netscript(char *agiurl, char *argv[], int *fds)
return AGI_RESULT_FAILURE;
}
static enum agi_result launch_script(struct ast_channel *chan, char *script, int argc, char *argv[], int *fds, int *efd, int *opid)
static enum agi_result launch_script(struct ast_channel *chan, char *script, int argc, char *argv[], int *fds, int *efd, int *opid, int *safe_fork_called)
{
char tmp[256];
int pid, toast[2], fromast[2], audio[2], res;
struct stat st;
/* We should not call ast_safe_fork_cleanup() if we never call ast_safe_fork(1) */
*safe_fork_called = 0;
if (!strncasecmp(script, "agi://", 6)) {
return (efd == NULL) ? launch_netscript(script, argv, fds) : AGI_RESULT_FAILURE;
}
@@ -2252,6 +2255,8 @@ static enum agi_result launch_script(struct ast_channel *chan, char *script, int
}
}
*safe_fork_called = 1;
if ((pid = ast_safe_fork(1)) < 0) {
ast_log(LOG_WARNING, "Failed to fork(): %s\n", strerror(errno));
return AGI_RESULT_FAILURE;
@@ -4531,6 +4536,7 @@ static int agi_exec_full(struct ast_channel *chan, const char *data, int enhance
enum agi_result res;
char *buf;
int fds[2], efd = -1, pid = -1;
int safe_fork_called = 0;
AST_DECLARE_APP_ARGS(args,
AST_APP_ARG(arg)[MAX_ARGS];
);
@@ -4553,7 +4559,7 @@ static int agi_exec_full(struct ast_channel *chan, const char *data, int enhance
return -1;
}
#endif
res = launch_script(chan, args.arg[0], args.argc, args.arg, fds, enhanced ? &efd : NULL, &pid);
res = launch_script(chan, args.arg[0], args.argc, args.arg, fds, enhanced ? &efd : NULL, &pid, &safe_fork_called);
/* Async AGI do not require run_agi(), so just proceed if normal AGI
or Fast AGI are setup with success. */
if (res == AGI_RESULT_SUCCESS || res == AGI_RESULT_SUCCESS_FAST) {
@@ -4571,7 +4577,9 @@ static int agi_exec_full(struct ast_channel *chan, const char *data, int enhance
if (efd > -1)
close(efd);
}
if (safe_fork_called) {
ast_safe_fork_cleanup();
}
switch (res) {
case AGI_RESULT_SUCCESS: