Commit 14fc9fbc authored by Hiroshi Shimamoto's avatar Hiroshi Shimamoto Committed by Ingo Molnar
Browse files

x86: signal: check signal stack overflow properly 



Impact: cleanup

Check alternate signal stack overflow with proper stack pointer.
The stack pointer of the next signal frame is different if that
task has i387 state.

On x86_64, redzone would be included.

No need to check SA_ONSTACK if we're already using alternate signal stack.

Signed-off-by: default avatarHiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Roland McGrath <roland@redhat.com>
LKML-Reference: <49C2874D.3080002@ct.jp.nec.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7f00a249

arch/x86/kernel/signal.c

+27 −21
Original line number Diff line number Diff line
@@ -211,19 +211,14 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, 
{

	/* Default to using normal stack */

	unsigned long sp = regs->sp;

	int onsigstack = on_sig_stack(sp);



#ifdef CONFIG_X86_64

	/* redzone */

	sp -= 128;

#endif /* CONFIG_X86_64 */



	/*

	 * If we are on the alternate signal stack and would overflow it, don't.

	 * Return an always-bogus address instead so we will die with SIGSEGV.

	 */

	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))

		return (void __user *) -1L;



	if (!onsigstack) {

		/* This is the X/Open sanctioned signal stack switching.  */

		if (ka->sa.sa_flags & SA_ONSTACK) {

			if (sas_ss_flags(sp) == 0)
@@ -237,6 +232,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, 
				sp = (unsigned long) ka->sa.sa_restorer;

#endif /* CONFIG_X86_32 */

		}

	}



	if (used_math()) {

		sp -= sig_xstate_size;
@@ -244,12 +240,22 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, 
		sp = round_down(sp, 64);

#endif /* CONFIG_X86_64 */

		*fpstate = (void __user *)sp;

	}



		if (save_i387_xstate(*fpstate) < 0)

	sp = align_sigframe(sp - frame_size);



	/*

	 * If we are on the alternate signal stack and would overflow it, don't.

	 * Return an always-bogus address instead so we will die with SIGSEGV.

	 */

	if (onsigstack && !likely(on_sig_stack(sp)))

		return (void __user *)-1L;



	/* save i387 state */

	if (used_math() && save_i387_xstate(*fpstate) < 0)

		return (void __user *)-1L;

	}



	return (void __user *)align_sigframe(sp - frame_size);

	return (void __user *)sp;

}



#ifdef CONFIG_X86_32

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