https://bugzilla.mindrot.org/show_bug.cgi?id=3690
Bug ID: 3690
Summary: sshd: root [priv] process sleeping leads to
unprivileged child proc zombie
Product: Portable OpenSSH
Version: -current
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P5
Component: sshd
Assignee: unassigned-b...@mindrot.org
Reporter: 546554...@qq.com
Created attachment 3814
--> https://bugzilla.mindrot.org/attachment.cgi?id=3814&action=edit
deadlock process call stack
In the `sshd.c` file, the `grace_alarm_handler()` signal handling
function calls `sigdie()`, which in turn calls `sshsigdie()`, and
within this call, functions such as `shlogv()`, `do_log()`,
`{openlog(), syslog(), closelog()}` are invoked. Similarly, within the
main thread, the `privsep_preauth()` function calls
`monitor_child_preauth()`, which then calls `auth_log()`, and this also
results in calls to `{openlog(), syslog(), closelog()}`.
Since these functions are not async-signal-safe and they utilize a
global lock named `syslog_lock`, this can lead to a recursive deadlock
(AA lock). As a result, the pre-authentication process may end up in a
zombie state and fail to exit.
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