From cd1231d7035fea894118d5155ff984cdaf1ac1a2 Mon Sep 17 00:00:00 2001
From: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Date: Wed, 21 Mar 2018 17:10:26 +0530
Subject: [PATCH] powerpc/perf: Prevent kernel address leak via
 perf_get_data_addr()

References: bsc#1056686
Patch-mainline: v4.17-rc1
Git-commit: cd1231d7035fea894118d5155ff984cdaf1ac1a2

Sampled Data Address Register (SDAR) is a 64-bit register that
contains the effective address of the storage operand of an
instruction that was being executed, possibly out-of-order, at or
around the time that the Performance Monitor alert occurred.

In certain scenario SDAR happen to contain the kernel address even for
userspace only sampling. Add checks to prevent it.

Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/perf/core-book3s.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 1e55ae2f2afd..a00b364fb9d7 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -198,6 +198,10 @@ static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp)
 
 	if (!(mmcra & MMCRA_SAMPLE_ENABLE) || sdar_valid)
 		*addrp = mfspr(SPRN_SDAR);
+
+	if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN) &&
+		is_kernel_addr(mfspr(SPRN_SDAR)))
+		*addrp = 0;
 }
 
 static bool regs_sihv(struct pt_regs *regs)
-- 
2.13.6