pid_namespace: make zap_pid_ns_processes() freezable

When the init of a pid namespace exits, zap_pid_ns_processes() waits
until all other pids in the namespace are freed. A tracer outside the
namespace that does not reap its traced zombies keeps those pids
allocated, so this wait has no upper bound, and while it lasts every
suspend attempt fails:

  Freezing user space processes failed after 20.006 seconds (2 tasks refusing to freeze, wq_busy=0):

Neither wait is freezable. The first loop sleeps in do_wait(), which
returns -ERESTARTSYS on the freezer's fake signal; the loop then clears
TIF_SIGPENDING and waits again without ever freezing. The final loop
sleeps in TASK_INTERRUPTIBLE, and since nothing clears TIF_SIGPENDING
there, schedule() returns immediately after the first freeze attempt
and the task spins until the wait ends.

Sleep in TASK_INTERRUPTIBLE | TASK_FREEZABLE in do_wait(), so that the
freezer can freeze tasks waiting there directly, and in TASK_IDLE |
TASK_FREEZABLE in the final loop, like coredump_task_exit() does.

This was hit with Chromium-based browsers: crashpad ptrace-attaches the
threads of a crashed renderer, which is a pid namespace init, and does
not reap those killed during the dump.

Fixes: 3eb07c8c8adb ("pid namespaces: destroy pid namespace on init's death")
Fixes: b9a985db9896 ("pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes")
Cc: stable@vger.kernel.org # 6.1+
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Aviv Vaknin <vaknins33@gmail.com>
Link: https://patch.msgid.link/20261002202820.3433318-1-vaknins33@gmail.com
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions