From c1fa0768a8713b135848f78fd43ffc208d8ded70 Mon Sep 17 00:00:00 2001
From: Gustavo Romero <gromero@linux.vnet.ibm.com>
Date: Wed, 13 Sep 2017 22:13:48 -0400
Subject: [PATCH] powerpc/tm: Flush TM only if CPU has TM feature
References: bsc#1075746, bsc#1087231, CVE-2018-1091
Patch-mainline: v4.14-rc2
Git-commit: c1fa0768a8713b135848f78fd43ffc208d8ded70
Commit cd63f3c ("powerpc/tm: Fix saving of TM SPRs in core dump")
added code to access TM SPRs in flush_tmregs_to_thread(). However
flush_tmregs_to_thread() does not check if TM feature is available on
CPU before trying to access TM SPRs in order to copy live state to
thread structures. flush_tmregs_to_thread() is indeed guarded by
CONFIG_PPC_TRANSACTIONAL_MEM but it might be the case that kernel
was compiled with CONFIG_PPC_TRANSACTIONAL_MEM enabled and ran on
a CPU without TM feature available, thus rendering the execution
of TM instructions that are treated by the CPU as illegal instructions.
The fix is just to add proper checking in flush_tmregs_to_thread()
if CPU has the TM feature before accessing any TM-specific resource,
returning immediately if TM is no available on the CPU. Adding
that checking in flush_tmregs_to_thread() instead of in places
where it is called, like in vsr_get() and vsr_set(), is better because
avoids the same problem cropping up elsewhere.
Cc: stable@vger.kernel.org # v4.13+
Fixes: cd63f3c ("powerpc/tm: Fix saving of TM SPRs in core dump")
Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>
Reviewed-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/ptrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 07cd22e35405..f52ad5bb7109 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -131,7 +131,7 @@ static void flush_tmregs_to_thread(struct task_struct *tsk)
* in the appropriate thread structures from live.
*/
- if (tsk != current)
+ if ((!cpu_has_feature(CPU_FTR_TM)) || (tsk != current))
return;
if (MSR_TM_SUSPENDED(mfmsr())) {
--
2.13.6