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Commit 4393c4f6 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt Committed by Paul Mackerras
Browse files

[POWERPC] Make alignment exception always check exception table 



The alignment exception used to only check the exception table for
-EFAULT, not for other errors. That opens an oops window if we can
coerce the kernel into getting an alignment exception for other reasons
in what would normally be a user-protected accessor, which can be done
via some of the futex ops. This fixes it by always checking the
exception tables.

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 0d69a052

arch/powerpc/kernel/traps.c

+10 −8
Original line number Original line Diff line number Diff line
@@ -843,7 +843,7 @@ void __kprobes program_check_exception(struct pt_regs *regs) 




void alignment_exception(struct pt_regs *regs)

void alignment_exception(struct pt_regs *regs)

{

{

	int fixed = 0;

	int sig, code, fixed = 0;





	/* we don't implement logging of alignment exceptions */

	/* we don't implement logging of alignment exceptions */

	if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))

	if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))
@@ -857,14 +857,16 @@ void alignment_exception(struct pt_regs *regs) 




	/* Operand address was bad */

	/* Operand address was bad */

	if (fixed == -EFAULT) {

	if (fixed == -EFAULT) {

		sig = SIGSEGV;

		code = SEGV_ACCERR;

	} else {

		sig = SIGBUS;

		code = BUS_ADRALN;

	}

	if (user_mode(regs))

	if (user_mode(regs))

			_exception(SIGSEGV, regs, SEGV_ACCERR, regs->dar);

		_exception(sig, regs, code, regs->dar);

	else

	else

			/* Search exception table */

		bad_page_fault(regs, regs->dar, sig);

			bad_page_fault(regs, regs->dar, SIGSEGV);

		return;

	}

	_exception(SIGBUS, regs, BUS_ADRALN, regs->dar);

}

}





void StackOverflow(struct pt_regs *regs)

void StackOverflow(struct pt_regs *regs)

arch/ppc/kernel/traps.c

+10 −8
Original line number Original line Diff line number Diff line
@@ -708,7 +708,7 @@ void single_step_exception(struct pt_regs *regs) 




void alignment_exception(struct pt_regs *regs)

void alignment_exception(struct pt_regs *regs)

{

{

	int fixed;

	int sig, code, fixed = 0;





	fixed = fix_alignment(regs);

	fixed = fix_alignment(regs);

	if (fixed == 1) {

	if (fixed == 1) {
@@ -717,14 +717,16 @@ void alignment_exception(struct pt_regs *regs) 
		return;

		return;

	}

	}

	if (fixed == -EFAULT) {

	if (fixed == -EFAULT) {

		/* fixed == -EFAULT means the operand address was bad */

		sig = SIGSEGV;

		code = SEGV_ACCERR;

	} else {

		sig = SIGBUS;

		code = BUS_ADRALN;

	}

	if (user_mode(regs))

	if (user_mode(regs))

			_exception(SIGSEGV, regs, SEGV_ACCERR, regs->dar);

		_exception(sig, regs, code, regs->dar);

	else

	else

			bad_page_fault(regs, regs->dar, SIGSEGV);

		bad_page_fault(regs, regs->dar, sig);

		return;

	}

	_exception(SIGBUS, regs, BUS_ADRALN, regs->dar);

}

}





void StackOverflow(struct pt_regs *regs)

void StackOverflow(struct pt_regs *regs)