Commit-ID: 382005027fedc50b28d40ae64ef1461cca38953e Gitweb: http://git.kernel.org/tip/382005027fedc50b28d40ae64ef1461cca38953e Author: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> AuthorDate: Wed, 2 Nov 2016 19:50:29 +0900 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 3 Nov 2016 07:27:34 +0100
sched/core: Fix oops in sched_show_task() When CONFIG_THREAD_INFO_IN_TASK=y, it is possible that an exited thread remains in the task list after its stack pointer was already set to NULL. Therefore, thread_saved_pc() and stack_not_used() in sched_show_task() will trigger NULL pointer dereference if an attempt to dump such thread's traces (e.g. SysRq-t, khungtaskd) is made. Since show_stack() in sched_show_task() calls try_get_task_stack() and sched_show_task() is called from interrupt context, calling try_get_task_stack() from sched_show_task() will be safe as well. Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Acked-by: Andy Lutomirski <l...@kernel.org> Acked-by: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: b...@alien8.de Cc: brge...@gmail.com Cc: j...@thejh.net Cc: keesc...@chromium.org Cc: linux-...@vger.kernel.org Cc: tycho.ander...@canonical.com Link: http://lkml.kernel.org/r/201611021950.fej34368.hffjoomltqo...@i-love.sakura.ne.jp Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 42d4027..9abf66b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5192,6 +5192,8 @@ void sched_show_task(struct task_struct *p) int ppid; unsigned long state = p->state; + if (!try_get_task_stack(p)) + return; if (state) state = __ffs(state) + 1; printk(KERN_INFO "%-15.15s %c", p->comm, @@ -5221,6 +5223,7 @@ void sched_show_task(struct task_struct *p) print_worker_info(KERN_INFO, p); show_stack(p, NULL); + put_task_stack(p); } void show_state_filter(unsigned long state_filter)
