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process-util: add new FORK_DEATHSIG_SIGKILL flag, rename FORK_DEATHSIG → FORK_DEATHSIG_SIGTERM

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Sometimes it makes sense to hard kill a client if we die. Let's hence
add a third FORK_DEATHSIG flag for this purpose: FORK_DEATHSIG_SIGKILL.

To make things less confusing this also renames FORK_DEATHSIG to
FORK_DEATHSIG_SIGTERM to make clear it sends SIGTERM. We already had
FORK_DEATHSIG_SIGINT, hence this makes things nicely symmetric.

A bunch of users are switched over for FORK_DEATHSIG_SIGKILL where we
know it's safe to abort things abruptly. This should make some kernel
cases more robust, since we cannot get confused by signal masks or such.

While we are at it, also fix a bunch of bugs where we didn't take
FORK_DEATHSIG_SIGINT into account in safe_fork()
This commit is contained in:
Lennart Poettering
2023-11-02 14:09:23 +01:00
parent 61c062f896
commit e9ccae3135
65 changed files with 125 additions and 116 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/process-util.c
+17 -9
View File
@@ -1380,6 +1380,12 @@ pid_t clone_with_nested_stack(int (*fn)(void *), int flags, void *userdata) {
return pid;
}
static int fork_flags_to_signal(ForkFlags flags) {
return (flags & FORK_DEATHSIG_SIGTERM) ? SIGTERM :
(flags & FORK_DEATHSIG_SIGINT) ? SIGINT :
SIGKILL;
}
int safe_fork_full(
const char *name,
const int stdio_fds[3],
@@ -1409,9 +1415,10 @@ int safe_fork_full(
fflush(stderr); /* This one shouldn't be necessary, stderr should be unbuffered anyway, but let's better be safe than sorry */
}
if (flags & (FORK_RESET_SIGNALS|FORK_DEATHSIG)) {
/* We temporarily block all signals, so that the new child has them blocked initially. This way, we can
* be sure that SIGTERMs are not lost we might send to the child. */
if (flags & (FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM|FORK_DEATHSIG_SIGINT)) {
/* We temporarily block all signals, so that the new child has them blocked initially. This
* way, we can be sure that SIGTERMs are not lost we might send to the child. (Note that for
* FORK_DEATHSIG_SIGKILL we don't bother, since it cannot be blocked anyway.) */
assert_se(sigfillset(&ss) >= 0);
block_signals = block_all = true;
@@ -1512,8 +1519,8 @@ int safe_fork_full(
r, "Failed to rename process, ignoring: %m");
}
if (flags & (FORK_DEATHSIG|FORK_DEATHSIG_SIGINT))
if (prctl(PR_SET_PDEATHSIG, (flags & FORK_DEATHSIG_SIGINT) ? SIGINT : SIGTERM) < 0) {
if (flags & (FORK_DEATHSIG_SIGTERM|FORK_DEATHSIG_SIGINT|FORK_DEATHSIG_SIGKILL))
if (prctl(PR_SET_PDEATHSIG, fork_flags_to_signal(flags)) < 0) {
log_full_errno(prio, errno, "Failed to set death signal: %m");
_exit(EXIT_FAILURE);
}
@@ -1538,7 +1545,7 @@ int safe_fork_full(
}
}
if (flags & FORK_DEATHSIG) {
if (flags & (FORK_DEATHSIG_SIGTERM|FORK_DEATHSIG_SIGKILL|FORK_DEATHSIG_SIGINT)) {
pid_t ppid;
/* Let's see if the parent PID is still the one we started from? If not, then the parent
* already died by the time we set PR_SET_PDEATHSIG, hence let's emulate the effect */
@@ -1547,8 +1554,9 @@ int safe_fork_full(
if (ppid == 0)
/* Parent is in a different PID namespace. */;
else if (ppid != original_pid) {
log_debug("Parent died early, raising SIGTERM.");
(void) raise(SIGTERM);
int sig = fork_flags_to_signal(flags);
log_debug("Parent died early, raising %s.", signal_to_string(sig));
(void) raise(sig);
_exit(EXIT_FAILURE);
}
}
@@ -1664,7 +1672,7 @@ int namespace_fork(
r = safe_fork_full(outer_name,
NULL,
except_fds, n_except_fds,
(flags|FORK_DEATHSIG) & ~(FORK_REOPEN_LOG|FORK_NEW_MOUNTNS|FORK_MOUNTNS_SLAVE), ret_pid);
(flags|FORK_DEATHSIG_SIGINT|FORK_DEATHSIG_SIGTERM|FORK_DEATHSIG_SIGKILL) & ~(FORK_REOPEN_LOG|FORK_NEW_MOUNTNS|FORK_MOUNTNS_SLAVE), ret_pid);
if (r < 0)
return r;
if (r == 0) {