| From | Luis Henriques <> | Subject | [PATCH 3.11 136/182] exit: call disassociate_ctty() before exit_task_namespaces() | Date | Thu, 24 Apr 2014 09:51:01 +0100 |
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3.11.10.9 -stable review patch. If anyone has any objections, please let me know.
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From: Oleg Nesterov <oleg@redhat.com>
commit c39df5fa37b0623589508c95515b4aa1531c524e upstream.
Commit 8aac62706ada ("move exit_task_namespaces() outside of exit_notify()") breaks pppd and the exiting service crashes the kernel:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000028 IP: ppp_register_channel+0x13/0x20 [ppp_generic] Call Trace: ppp_asynctty_open+0x12b/0x170 [ppp_async] tty_ldisc_open.isra.2+0x27/0x60 tty_ldisc_hangup+0x1e3/0x220 __tty_hangup+0x2c4/0x440 disassociate_ctty+0x61/0x270 do_exit+0x7f2/0xa50
ppp_register_channel() needs ->net_ns and current->nsproxy == NULL.
Move disassociate_ctty() before exit_task_namespaces(), it doesn't make sense to delay it after perf_event_exit_task() or cgroup_exit().
This also allows to use task_work_add() inside the (nontrivial) code paths in disassociate_ctty().
Investigated by Peter Hurley.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Sree Harsha Totakura <sreeharsha@totakura.in> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Sree Harsha Totakura <sreeharsha@totakura.in> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Andrey Vagin <avagin@openvz.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- kernel/exit.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c index a949819..b79d882 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -783,6 +783,8 @@ void do_exit(long code) exit_shm(tsk); exit_files(tsk); exit_fs(tsk); + if (group_dead) + disassociate_ctty(1); exit_task_namespaces(tsk); exit_task_work(tsk); check_stack_usage(); @@ -798,13 +800,9 @@ void do_exit(long code) cgroup_exit(tsk, 1); - if (group_dead) - disassociate_ctty(1); - module_put(task_thread_info(tsk)->exec_domain->module); proc_exit_connector(tsk); - /* * FIXME: do that only when needed, using sched_exit tracepoint */ -- 1.9.1
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