Public issue detail
sshd-auth is stuck in a likely busy poll loop: 100.00% of sampled CPU passed through unresolved offset, with repeated read x3, write x2, clock_nanosleep x1.
Last seen: 2026-10-22 20:40 UTC. Public JSON: /v1/issues/019e1519-78c6-7813-bebb-aeb6177e1897
This diff is preserved as useful evidence, but a manual disposition supersedes the original harvest blockers. Use the patch to understand the failure mode; do not send it upstream unchanged.
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report and patch proposal were created locally.
sshd-auth: enforce LoginGraceTime during pre-authenticationCommit message.
Fixer observed `sshd-auth`, the split helper that handles pre-authentication SSH key exchange and user authentication, in a short trace around sleep, monitor writes, and `ppoll`. The trace does not prove an infinite spin, but it does show the pre-auth helper in the area that should be bounded by `LoginGraceTime`.
`sshd-session.c` already arms that timer before pre-authentication. Mirror that bounded timer setup in `sshd-auth.c`, and clear it after authentication succeeds.
Problem. sshd-auth is stuck in a likely busy poll loop: 100.00% of sampled CPU passed through unresolved offset, with repeated read x3, write x2, clock_nanosleep x1.
How this patch connects to the issue.
Fixer observed an `sshd-auth: root [net]` process with profiler evidence in `sshd-auth`, a dominant syscall sequence of `clock_nanosleep`, `write`, and `ppoll`, `/proc` state sleeping in `unix_stream_read_generic`, and a captured strace ending with `ECONNRESET` and exit. This was observed by Fixer and not independently reproduced.
The cautious code-level cause is that split `sshd-auth.c` reset `SIGALRM` to the default action and then entered key exchange and authentication without arming the configured `LoginGraceTime` alarm. I improved the prior Fixer patch by keeping the same bounded linear control flow, cleaning up style, and adding only the timer setup/clear logic already used by the nearby session path.
The change uses existing OpenSSH conventions and helpers: `ssh_signal`, `setitimer`, `timerclear`, `arc4random_uniform`, `fatal`, and `_exit(EXIT_LOGIN_GRACE)`. `README.md` was the only contribution/style document found; no relevant local file-I/O, path, process-spawn, allocation, or locking helper was needed for this change. The expected effect is that slow or wedged `sshd-auth` pre-authentication workers are terminated by the configured login grace timeout instead of being allowed to remain in pre-authentication indefinitely.
sshd-auth.cmanual fixer defect: Do not submit retained LoginGraceTime patch; current upstream already arms the parent-side LoginGraceTime alarm unless a reproducer proves bypass.
These blockers remain on the preserved local diff, but the manual disposition above is the current handoff.
diff --git a/sshd-auth.c b/sshd-auth.c
index 502a342..07384ca 100644
--- a/sshd-auth.c
+++ b/sshd-auth.c
@@ -175,6 +175,17 @@ mm_is_monitor(void)
return 0;
}
+/*
+ * Signal handler for the alarm after the login grace period has expired.
+ * As usual, this may only take signal-safe actions, even though it is
+ * terminal.
+ */
+static void
+grace_alarm_handler(int sig)
+{
+ _exit(EXIT_LOGIN_GRACE);
+}
+
static void
privsep_child_demote(void)
{
@@ -445,6 +456,7 @@ main(int ac, char **av)
Authctxt *authctxt;
struct connection_info *connection_info = NULL;
sigset_t sigmask;
+ struct itimerval itv;
uint64_t timing_secret = 0;
closefrom(PRIVSEP_MIN_FREE_FD);
@@ -725,6 +737,27 @@ main(int ac, char **av)
ssh_signal(SIGQUIT, SIG_DFL);
ssh_signal(SIGCHLD, SIG_DFL);
+ /*
+ * We don't want to listen forever unless the other side
+ * successfully authenticates itself. So we set up an alarm which is
+ * cleared after successful authentication. A limit of zero
+ * indicates no limit. Note that we don't set the alarm in debugging
+ * mode; it is just annoying to have the server exit just when you
+ * are about to discover the bug.
+ */
+ ssh_signal(SIGALRM, grace_alarm_handler);
+ if (!debug_flag && options.login_grace_time > 0) {
+ int ujitter = arc4random_uniform(4 * 1000000);
+
+ timerclear(&itv.it_interval);
+ itv.it_value.tv_sec = options.login_grace_time;
+ itv.it_value.tv_sec += ujitter / 1000000;
+ itv.it_value.tv_usec = ujitter % 1000000;
+
+ if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
+ fatal("login grace time setitimer failed");
+ }
+
/* Prepare the channels layer */
channel_init_channels(ssh);
channel_set_af(ssh, options.address_family);
@@ -761,6 +794,16 @@ main(int ac, char **av)
do_ssh2_kex(ssh);
do_authentication2(ssh);
+ /*
+ * Cancel the alarm we set to limit the time taken for
+ * authentication.
+ */
+ timerclear(&itv.it_interval);
+ timerclear(&itv.it_value);
+ if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
+ fatal("login grace time clear failed");
+ ssh_signal(SIGALRM, SIG_DFL);
+
/*
* The unprivileged child now transfers the current keystate and exits.
*/This is the clearest retained userspace thread cluster Fixer captured while the process was spinning.
unix_stream_read_generic
unix_stream_recvmsg
sock_recvmsg
sock_read_iter
vfs_read
ksys_read
do_syscall_64
entry_SYSCALL_64_after_hwframeThese are suggestions based on sanitized trigram similarity plus structured fields like package, subsystem, classification, and wait site. They are not auto-merged.
sshd-auth is stuck in a likely busy poll loop: 100.00% of sampled CPU passed through tcp_event_new_data_sent, with repeated read x5, write x5, clock_nanosleep x2.
Why this looks related: same classification, same package, same source package, same subsystem, same target, same wait site
Last seen: 2026-10-22 19:58 UTC. Public page: /issues/019e5b4d-626d-7493-8c66-015e945a13ab. Public JSON: /v1/issues/019e5b4d-626d-7493-8c66-015e945a13ab
sshd-session is stuck in a likely unclassified userspace loop: 19.46% of sampled CPU passed through unresolved offset, with repeated thread backtraces show 1 thread(s) around 0x00007f19f549a7d2 in ?? () from target:<path>.
Why this looks related: same package, same source package, same subsystem
Last seen: 2026-10-22 20:40 UTC. Public page: /issues/019e5500-abf8-7a11-8504-fbba3c540a4f. Public JSON: /v1/issues/019e5500-abf8-7a11-8504-fbba3c540a4f
sshd-session is stuck in a likely unclassified userspace loop: 100.00% of sampled CPU passed through sock_poll, with repeated thread backtraces show 1 thread(s) around 0x00007f35fa09a7d2 in ?? () from target:<path>.
Why this looks related: same package, same source package, same subsystem
Last seen: 2026-10-22 19:58 UTC. Public page: /issues/019dff15-4a95-7fb3-b680-40595c35ee68. Public JSON: /v1/issues/019dff15-4a95-7fb3-b680-40595c35ee68
sshd-session is stuck in a likely unclassified userspace loop: 21.93% of sampled CPU passed through locks_remove_file, with repeated thread backtraces show 1 thread(s) around 0x00007f726ec9a7d2 in ?? () from target:<path>.
Why this looks related: same package, same source package, same subsystem
Last seen: 2026-10-22 19:58 UTC. Public page: /issues/019e6049-7500-76f3-8131-a20112312129. Public JSON: /v1/issues/019e6049-7500-76f3-8131-a20112312129
sshd-session is stuck in a likely unclassified userspace loop: 10.43% of sampled CPU passed through truncate_inode_pages_range, with repeated thread backtraces show 1 thread(s) around 0x00007f2b2e89a7d2 in ?? () from target:<path>.
Why this looks related: same package, same source package, same subsystem
Last seen: 2026-10-22 19:58 UTC. Public page: /issues/019e5b4d-6246-75b1-9f7c-e4a8d5a2e4a9. Public JSON: /v1/issues/019e5b4d-6246-75b1-9f7c-e4a8d5a2e4a9
This issue has 772 recorded worker attempts. Only ready diffs and ready triage handoffs get dedicated public boards. Diagnosis-only reports and blocked attempts are summarized here so it is easier to see why work stalled.
No explained impossible attempts or other attempt states.
Showing the 25 most recent attempts below and summarizing 747 older attempts here. Show all published attempts for this issue.
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked
sshd-auth likely remains stuck in a busy-poll loop. A diagnosis report was created, but the automated patch attempt stopped before completion: No such file or directory (os error 2)
automatic-patch-blocked
Likely owner: external dependency or workload outside the current source tree
Reason: automatic-patch-blocked