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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Gustavo Romero <gromero@linux.ibm.com>,
	Michael Neuling <mikey@neuling.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Subject: [PATCH 5.2 15/37] powerpc/tm: Fix restoring FP/VMX facility incorrectly on interrupts
Date: Fri, 13 Sep 2019 14:07:20 +0100
Message-ID: <20190913130516.821238670@linuxfoundation.org> (raw)
In-Reply-To: <20190913130510.727515099@linuxfoundation.org>

From: Gustavo Romero <gromero@linux.ibm.com>

commit a8318c13e79badb92bc6640704a64cc022a6eb97 upstream.

When in userspace and MSR FP=0 the hardware FP state is unrelated to
the current process. This is extended for transactions where if tbegin
is run with FP=0, the hardware checkpoint FP state will also be
unrelated to the current process. Due to this, we need to ensure this
hardware checkpoint is updated with the correct state before we enable
FP for this process.

Unfortunately we get this wrong when returning to a process from a
hardware interrupt. A process that starts a transaction with FP=0 can
take an interrupt. When the kernel returns back to that process, we
change to FP=1 but with hardware checkpoint FP state not updated. If
this transaction is then rolled back, the FP registers now contain the
wrong state.

The process looks like this:
   Userspace:                      Kernel

               Start userspace
                with MSR FP=0 TM=1
                  < -----
   ...
   tbegin
   bne
               Hardware interrupt
                   ---- >
                                    <do_IRQ...>
                                    ....
                                    ret_from_except
                                      restore_math()
				        /* sees FP=0 */
                                        restore_fp()
                                          tm_active_with_fp()
					    /* sees FP=1 (Incorrect) */
                                          load_fp_state()
                                        FP = 0 -> 1
                  < -----
               Return to userspace
                 with MSR TM=1 FP=1
                 with junk in the FP TM checkpoint
   TM rollback
   reads FP junk

When returning from the hardware exception, tm_active_with_fp() is
incorrectly making restore_fp() call load_fp_state() which is setting
FP=1.

The fix is to remove tm_active_with_fp().

tm_active_with_fp() is attempting to handle the case where FP state
has been changed inside a transaction. In this case the checkpointed
and transactional FP state is different and hence we must restore the
FP state (ie. we can't do lazy FP restore inside a transaction that's
used FP). It's safe to remove tm_active_with_fp() as this case is
handled by restore_tm_state(). restore_tm_state() detects if FP has
been using inside a transaction and will set load_fp and call
restore_math() to ensure the FP state (checkpoint and transaction) is
restored.

This is a data integrity problem for the current process as the FP
registers are corrupted. It's also a security problem as the FP
registers from one process may be leaked to another.

Similarly for VMX.

A simple testcase to replicate this will be posted to
tools/testing/selftests/powerpc/tm/tm-poison.c

This fixes CVE-2019-15031.

Fixes: a7771176b439 ("powerpc: Don't enable FP/Altivec if not checkpointed")
Cc: stable@vger.kernel.org # 4.15+
Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190904045529.23002-2-gromero@linux.vnet.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/process.c |   18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -101,21 +101,8 @@ static void check_if_tm_restore_required
 	}
 }
 
-static bool tm_active_with_fp(struct task_struct *tsk)
-{
-	return MSR_TM_ACTIVE(tsk->thread.regs->msr) &&
-		(tsk->thread.ckpt_regs.msr & MSR_FP);
-}
-
-static bool tm_active_with_altivec(struct task_struct *tsk)
-{
-	return MSR_TM_ACTIVE(tsk->thread.regs->msr) &&
-		(tsk->thread.ckpt_regs.msr & MSR_VEC);
-}
 #else
 static inline void check_if_tm_restore_required(struct task_struct *tsk) { }
-static inline bool tm_active_with_fp(struct task_struct *tsk) { return false; }
-static inline bool tm_active_with_altivec(struct task_struct *tsk) { return false; }
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 
 bool strict_msr_control;
@@ -252,7 +239,7 @@ EXPORT_SYMBOL(enable_kernel_fp);
 
 static int restore_fp(struct task_struct *tsk)
 {
-	if (tsk->thread.load_fp || tm_active_with_fp(tsk)) {
+	if (tsk->thread.load_fp) {
 		load_fp_state(&current->thread.fp_state);
 		current->thread.load_fp++;
 		return 1;
@@ -334,8 +321,7 @@ EXPORT_SYMBOL_GPL(flush_altivec_to_threa
 
 static int restore_altivec(struct task_struct *tsk)
 {
-	if (cpu_has_feature(CPU_FTR_ALTIVEC) &&
-		(tsk->thread.load_vec || tm_active_with_altivec(tsk))) {
+	if (cpu_has_feature(CPU_FTR_ALTIVEC) && (tsk->thread.load_vec)) {
 		load_vr_state(&tsk->thread.vr_state);
 		tsk->thread.used_vr = 1;
 		tsk->thread.load_vec++;



  parent reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-13 13:07 [PATCH 5.2 00/37] 5.2.15-stable review Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 01/37] gpio: pca953x: correct type of reg_direction Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 02/37] gpio: pca953x: use pca953x_read_regs instead of regmap_bulk_read Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 03/37] ALSA: hda - Fix potential endless loop at applying quirks Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 04/37] ALSA: hda/realtek - Fix overridden device-specific initialization Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 05/37] ALSA: hda/realtek - Add quirk for HP Pavilion 15 Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 06/37] ALSA: hda/realtek - Enable internal speaker & headset mic of ASUS UX431FL Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 07/37] ALSA: hda/realtek - Fix the problem of two front mics on a ThinkCentre Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 08/37] sched/fair: Dont assign runtime for throttled cfs_rq Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 09/37] drm/vmwgfx: Fix double free in vmw_recv_msg() Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 10/37] drm/nouveau/sec2/gp102: add missing MODULE_FIRMWAREs Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 11/37] vhost/test: fix build for vhost test Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 12/37] vhost/test: fix build for vhost test - again Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 13/37] powerpc/64e: Drop stale call to smp_processor_id() which hangs SMP startup Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 14/37] powerpc/tm: Fix FP/VMX unavailable exceptions inside a transaction Greg Kroah-Hartman
2019-09-13 13:07 ` Greg Kroah-Hartman [this message]
2019-09-13 13:07 ` [PATCH 5.2 16/37] batman-adv: fix uninit-value in batadv_netlink_get_ifindex() Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 17/37] batman-adv: Only read OGM tvlv_len after buffer len check Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 18/37] bcache: only clear BTREE_NODE_dirty bit when it is set Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 19/37] bcache: add comments for mutex_lock(&b->write_lock) Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 20/37] bcache: fix race in btree_flush_write() Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 21/37] IB/rdmavt: Add new completion inline Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 22/37] IB/{rdmavt, qib, hfi1}: Convert to new completion API Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 23/37] IB/hfi1: Unreserve a flushed OPFN request Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 24/37] drm/i915: Disable SAMPLER_STATE prefetching on all Gen11 steppings Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 25/37] drm/i915: Make sure cdclk is high enough for DP audio on VLV/CHV Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 26/37] mmc: sdhci-sprd: Fix the incorrect soft reset operation when runtime resuming Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 27/37] usb: chipidea: imx: add imx7ulp support Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 28/37] usb: chipidea: imx: fix EPROBE_DEFER support during driver probe Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 29/37] virtio/s390: fix race on airq_areas[] Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 30/37] drm/i915: Support flags in whitlist WAs Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 31/37] drm/i915: Support whitelist workarounds on all engines Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 32/37] drm/i915: whitelist PS_(DEPTH|INVOCATION)_COUNT Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 33/37] drm/i915: Add whitelist workarounds for ICL Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 34/37] drm/i915/icl: whitelist PS_(DEPTH|INVOCATION)_COUNT Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 35/37] Btrfs: fix unwritten extent buffers and hangs on future writeback attempts Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 36/37] vhost: block speculation of translated descriptors Greg Kroah-Hartman
2019-09-14  0:54   ` Stefan Lippers-Hollmann
2019-09-14  5:50     ` Greg Kroah-Hartman
2019-09-14  7:15       ` Stefan Lippers-Hollmann
2019-09-14  8:08         ` Greg Kroah-Hartman
2019-09-15  9:34           ` Thomas Backlund
2019-09-15 13:37             ` Greg Kroah-Hartman
2019-09-13 13:07 ` [PATCH 5.2 37/37] vhost: make sure log_num < in_num Greg Kroah-Hartman
2019-09-13 19:39 ` [PATCH 5.2 00/37] 5.2.15-stable review kernelci.org bot
2019-09-14  4:26 ` Naresh Kamboju
2019-09-14  7:43   ` Greg Kroah-Hartman
2019-09-14 14:08 ` Guenter Roeck
2019-09-15 13:34 ` Greg Kroah-Hartman
2019-09-16  9:25 ` Jon Hunter
2019-09-16 10:41   ` Greg Kroah-Hartman

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