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authorOleg Nesterov <oleg@redhat.com>2014-04-07 15:38:29 -0700
committerJiri Slaby <jslaby@suse.cz>2014-05-05 14:24:47 +0200
commit61fae6dfba003b302fb16e26e8f815b984ac3e2d (patch)
treecb6dbffd9b742983fded82e105ac3729a52c43fd
parentf3e9310e26ff2391d9007c2c47bd88a720e62c37 (diff)
exit: call disassociate_ctty() before exit_task_namespaces()
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: Jiri Slaby <jslaby@suse.cz>
-rw-r--r--kernel/exit.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 92d7823648f8..dcde2c4b61d0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -790,6 +790,8 @@ 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();
@@ -805,13 +807,9 @@ 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
*/