Commit 8b9c6b28 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

signal/ia64: Use the generic force_sigsegv in setup_frame 



The ia64 handling of failure to setup a signal frame has been trying
to set overlapping fields in struct siginfo since 2.3.43.  The si_pid
and si_uid fields are stomped when the si_addr field is set.  The
si_code of SI_KERNEL indicates that si_pid and si_uid should be valid,
and that si_addr does not exist.

Being at odds with the definition of SI_KERNEL and with nothing to
indicate that this was a signal frame setup failure there is no way
for userspace to know that si_addr was filled out instead.

In practice failure to setup a signal frame is rare, and si_pid and
si_uid are always set to 0 when si_code is SI_KERNEL so I expect no
one has looked closely enough before to see this weirdness.  Further
the only difference between force_sigsegv_info and the generic
force_sigsegv other than the return code is that force_sigsegv_info
stomps the si_uid and si_pid fields.

Remove the bug and simplify the code by using force_sigsegv in this
case just like other architectures.

Fixes: 2.3.43
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Acked-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 795a8371

arch/ia64/kernel/signal.c

+12 −38
Original line number Diff line number Diff line
@@ -231,37 +231,6 @@ rbs_on_sig_stack (unsigned long bsp) 
	return (bsp - current->sas_ss_sp < current->sas_ss_size);

}



static long

force_sigsegv_info (int sig, void __user *addr)

{

	unsigned long flags;

	struct siginfo si;



	clear_siginfo(&si);

	if (sig == SIGSEGV) {

		/*

		 * Acquiring siglock around the sa_handler-update is almost

		 * certainly overkill, but this isn't a

		 * performance-critical path and I'd rather play it safe

		 * here than having to debug a nasty race if and when

		 * something changes in kernel/signal.c that would make it

		 * no longer safe to modify sa_handler without holding the

		 * lock.

		 */

		spin_lock_irqsave(&current->sighand->siglock, flags);

		current->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;

		spin_unlock_irqrestore(&current->sighand->siglock, flags);

	}

	si.si_signo = SIGSEGV;

	si.si_errno = 0;

	si.si_code = SI_KERNEL;

	si.si_pid = task_pid_vnr(current);

	si.si_uid = from_kuid_munged(current_user_ns(), current_uid());

	si.si_addr = addr;

	force_sig_info(SIGSEGV, &si, current);

	return 1;

}



static long

setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr)

{
@@ -295,15 +264,18 @@ setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr) 
			 * instead so we will die with SIGSEGV.

			 */

			check_sp = (new_sp - sizeof(*frame)) & -STACK_ALIGN;

			if (!likely(on_sig_stack(check_sp)))

				return force_sigsegv_info(ksig->sig, (void __user *)

							  check_sp);

			if (!likely(on_sig_stack(check_sp))) {

				force_sigsegv(ksig->sig, current);

				return 1;

			}

		}

	}

	frame = (void __user *) ((new_sp - sizeof(*frame)) & -STACK_ALIGN);



	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))

		return force_sigsegv_info(ksig->sig, frame);

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {

		force_sigsegv(ksig->sig, current);

		return 1;

	}



	err  = __put_user(ksig->sig, &frame->arg0);

	err |= __put_user(&frame->info, &frame->arg1);
@@ -317,8 +289,10 @@ setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr) 
	err |= __save_altstack(&frame->sc.sc_stack, scr->pt.r12);

	err |= setup_sigcontext(&frame->sc, set, scr);



	if (unlikely(err))

		return force_sigsegv_info(ksig->sig, frame);

	if (unlikely(err)) {

		force_sigsegv(ksig->sig, current);

		return 1;

	}



	scr->pt.r12 = (unsigned long) frame - 16;	/* new stack pointer */

	scr->pt.ar_fpsr = FPSR_DEFAULT;			/* reset fpsr for signal handler */

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