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From: Michael Ellerman <mpe@ellerman.id.au>
To: linuxppc-dev@ozlabs.org
Cc: mikey@neuling.org, benh@kernel.crashing.org,
	stewart@linux.vnet.ibm.com, cyrilbur@gmail.com
Subject: [PATCH 4/4] powerpc/tm: P9 disable transactionally suspended sigcontexts
Date: Thu, 12 Oct 2017 21:17:19 +1100	[thread overview]
Message-ID: <1507803439-12862-4-git-send-email-mpe@ellerman.id.au> (raw)
In-Reply-To: <1507803439-12862-1-git-send-email-mpe@ellerman.id.au>

From: Michael Neuling <mikey@neuling.org>

Unfortunately userspace can construct a sigcontext which enables
suspend. Thus userspace can force Linux into a path where trechkpt is
executed.

This patch blocks this from happening on POWER9 by sanity checking
sigcontexts passed in.

ptrace doesn't have this problem as only MSR SE and BE can be changed
via ptrace.

This patch also adds a number of WARN_ON() in case we ever enter
suspend when we shouldn't. This should catch systems that don't have
the firmware change and are running TM.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/kernel/process.c   | 2 ++
 arch/powerpc/kernel/signal_32.c | 4 ++++
 arch/powerpc/kernel/signal_64.c | 5 +++++
 3 files changed, 11 insertions(+)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index b02807ea54dc..c051dc2b42ad 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -910,6 +910,8 @@ static inline void tm_reclaim_task(struct task_struct *tsk)
 	if (!MSR_TM_ACTIVE(thr->regs->msr))
 		goto out_and_saveregs;
 
+	WARN_ON(tm_suspend_disabled);
+
 	TM_DEBUG("--- tm_reclaim on pid %d (NIP=%lx, "
 		 "ccr=%lx, msr=%lx, trap=%lx)\n",
 		 tsk->pid, thr->regs->nip,
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 92fb1c8dbbd8..1dd5fa0f65fd 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -519,6 +519,8 @@ static int save_tm_user_regs(struct pt_regs *regs,
 {
 	unsigned long msr = regs->msr;
 
+	WARN_ON(tm_suspend_disabled);
+
 	/* Remove TM bits from thread's MSR.  The MSR in the sigcontext
 	 * just indicates to userland that we were doing a transaction, but we
 	 * don't want to return in transactional state.  This also ensures
@@ -769,6 +771,8 @@ static long restore_tm_user_regs(struct pt_regs *regs,
 	int i;
 #endif
 
+	if (tm_suspend_disabled)
+		return 1;
 	/*
 	 * restore general registers but not including MSR or SOFTE. Also
 	 * take care of keeping r2 (TLS) intact if not a signal.
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index c83c115858c1..4dfdd8e56836 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -214,6 +214,8 @@ static long setup_tm_sigcontexts(struct sigcontext __user *sc,
 
 	BUG_ON(!MSR_TM_ACTIVE(regs->msr));
 
+	WARN_ON(tm_suspend_disabled);
+
 	/* Remove TM bits from thread's MSR.  The MSR in the sigcontext
 	 * just indicates to userland that we were doing a transaction, but we
 	 * don't want to return in transactional state.  This also ensures
@@ -430,6 +432,9 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 
 	BUG_ON(tsk != current);
 
+	if (tm_suspend_disabled)
+		return -EINVAL;
+
 	/* copy the GPRs */
 	err |= __copy_from_user(regs->gpr, tm_sc->gp_regs, sizeof(regs->gpr));
 	err |= __copy_from_user(&tsk->thread.ckpt_regs, sc->gp_regs,
-- 
2.7.4

  parent reply	other threads:[~2017-10-12 10:17 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-12 10:17 [PATCH 1/4] powerpc/tm: Add commandline option to disable hardware transactional memory Michael Ellerman
2017-10-12 10:17 ` [PATCH 2/4] powerpc: Add PPC_FEATURE2_HTM_NO_SUSPEND Michael Ellerman
2017-10-12 10:17 ` [PATCH 3/4] powerpc/powernv: Enable TM without suspend if possible Michael Ellerman
2017-10-19 10:07   ` Florian Weimer
2017-10-19 12:04     ` Tulio Magno Quites Machado Filho
2017-10-19 12:45       ` Florian Weimer
2017-10-19 13:34     ` Tulio Magno Quites Machado Filho
2017-10-19 15:13       ` Adhemerval Zanella
2017-10-22  9:59         ` Michael Ellerman
2017-10-20  2:47       ` Michael Neuling
2017-10-22  9:48       ` Michael Ellerman
2017-10-22  9:54     ` Michael Ellerman
2017-10-12 10:17 ` Michael Ellerman [this message]
2017-10-12 11:58 ` [PATCH 5/4] KVM: PPC: Tie KVM_CAP_PPC_HTM to the user-visible TM feature Michael Ellerman
2017-10-24  8:08   ` [5/4] " Michael Ellerman
2017-10-20 11:45 ` [PATCH 1/4] powerpc/tm: Add commandline option to disable hardware transactional memory Breno Leitao
2017-10-20 12:58   ` David Laight
2017-10-21  1:00     ` Michael Neuling
2017-10-23  9:01       ` David Laight
2017-10-23  9:15         ` Michael Neuling
2017-10-21  0:58   ` Michael Neuling
2017-10-23 12:56     ` Breno Leitao
2017-10-24  8:12       ` Michael Ellerman
2017-10-24  8:08 ` [1/4] " Michael Ellerman

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