[PATCH] ptrace: exit: re-trigger PTRACE_EVENT_EXIT after coredump finished

From: Vladimir Divjak
Date: Sun Nov 21 2021 - 20:01:14 EST


Re-trigger PTRACE_EVENT_EXIT
(if one is requested with PTRACE_SEIZE setting PTRACE_O_TRACEEXIT option)
for a process being core-dumped, after the coredump is finished.

This enables a potential tracer - coredump user mode helper
(or any other tracer started after the coredump was initiated)
to receive the PTRACE_EVENT_EXIT for all threads of the crashing process.

Rationale:

For zapped threads, PTRACE_EVENT_EXIT is triggered early during do_exit(),
before the point at which they sleep, waiting for
coredump to finish - in exit_mm(), and before a potential
coredump user mode helper process is launched.

That makes it impossible for the coredump user mode helper process to
receive PTRACE_EVENT_EXIT events for all threads of the crashing process,
except for the thread handling the core-dump, which will trigger
the PTRACE_EVENT_EXIT after the coredump has been finished.

Signed-off-by: Vladimir Divjak <vladimir.divjak@xxxxxx>
---
kernel/exit.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/exit.c b/kernel/exit.c
index fd1c04193e18..0157507e75a2 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -473,6 +473,13 @@ static void exit_mm(void)
break;
freezable_schedule();
}
+ /*
+ * Re-trigger PTRACE_EVENT_EXIT for a process being core-dumped,
+ * after the coredump finished (see above).
+ * This enables the coredump user mode helper to receive PTRACE_EVENT_EXIT
+ * for each thread of the dying process.
+ */
+ ptrace_event(PTRACE_EVENT_EXIT, current->exit_code);
__set_current_state(TASK_RUNNING);
mmap_read_lock(mm);
}
--
2.25.1