kthread uses stack and keeps completion structure on it to be woken up on vfork_done completion.
In commit 2deb4be28 Andy Lutomirski rewinds the stack unconditionally and further completion of task->vfork_done for any kthread leads to stack corruption (or infinite spin on attempt to spin lock on garbage memory). Signed-off-by: Roman Pen <roman.peny...@profitbricks.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@redhat.com> Cc: Tejun Heo <t...@kernel.org> Cc: x...@kernel.org Cc: linux-kernel@vger.kernel.org --- arch/x86/kernel/dumpstack.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index e0648f7..74be764 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -250,9 +250,14 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) /* * We're not going to return, but we might be on an IST stack or * have very little stack space left. Rewind the stack and kill - * the task. + * the task. But kthread is a special case, since kthread uses + * stack to keep completion structure to be woken on vfork_done + * completion. */ - rewind_stack_do_exit(signr); + if (current->flags & PF_KTHREAD) + do_exit(signr); + else + rewind_stack_do_exit(signr); } NOKPROBE_SYMBOL(oops_end); -- 2.9.3