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 <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Tejun Heo <[email protected]> Cc: [email protected] Cc: [email protected] --- 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
