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Subject[PATCH 4.19 032/639] signal/ia64: Use the generic force_sigsegv in setup_frame
Date
From: Eric W. Biederman <ebiederm@xmission.com>

[ Upstream commit 8b9c6b28312cc51a87055e292b11c5aa28f0c935 ]

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: Tony Luck <tony.luck@intel.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/ia64/kernel/signal.c | 50 ++++++++++-----------------------------
1 file changed, 12 insertions(+), 38 deletions(-)

diff --git a/arch/ia64/kernel/signal.c b/arch/ia64/kernel/signal.c
index d1234a5ba4c55..01fc133b2e4c8 100644
--- a/arch/ia64/kernel/signal.c
+++ b/arch/ia64/kernel/signal.c
@@ -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 */
--
2.20.1


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