Commit 2deb4be2 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/dumpstack: When OOPSing, rewind the stack before do_exit() 



If we call do_exit() with a clean stack, we greatly reduce the risk of
recursive oopses due to stack overflow in do_exit, and we allow
do_exit to work even if we OOPS from an IST stack.  The latter gives
us a much better chance of surviving long enough after we detect a
stack overflow to write out our logs.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/32f73ceb372ec61889598da5e5b145889b9f2e19.1468527351.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 46aea387

arch/x86/entry/entry_32.S

+11 −0
Original line number Diff line number Diff line
@@ -1153,3 +1153,14 @@ ENTRY(async_page_fault) 
	jmp	error_code

END(async_page_fault)

#endif



ENTRY(rewind_stack_do_exit)

	/* Prevent any naive code from trying to unwind to our caller. */

	xorl	%ebp, %ebp



	movl	PER_CPU_VAR(cpu_current_top_of_stack), %esi

	leal	-TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp



	call	do_exit

1:	jmp 1b

END(rewind_stack_do_exit)

arch/x86/entry/entry_64.S

+11 −0
Original line number Diff line number Diff line
@@ -1423,3 +1423,14 @@ ENTRY(ignore_sysret) 
	mov	$-ENOSYS, %eax

	sysret

END(ignore_sysret)



ENTRY(rewind_stack_do_exit)

	/* Prevent any naive code from trying to unwind to our caller. */

	xorl	%ebp, %ebp



	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rax

	leaq	-TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp



	call	do_exit

1:	jmp 1b

END(rewind_stack_do_exit)

arch/x86/kernel/dumpstack.c

+9 −1
Original line number Diff line number Diff line
@@ -234,6 +234,8 @@ unsigned long oops_begin(void) 
EXPORT_SYMBOL_GPL(oops_begin);

NOKPROBE_SYMBOL(oops_begin);



void __noreturn rewind_stack_do_exit(int signr);



void oops_end(unsigned long flags, struct pt_regs *regs, int signr)

{

	if (regs && kexec_should_crash(current))
@@ -255,7 +257,13 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) 
		panic("Fatal exception in interrupt");

	if (panic_on_oops)

		panic("Fatal exception");

	do_exit(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.

	 */

	rewind_stack_do_exit(signr);

}

NOKPROBE_SYMBOL(oops_end);

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