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Message-Id: <7f24b5961a6839ff01df792816807f74ff236bf6.1582567319.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH] powerpc/kprobes: Use probe_address() to read instructions
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        naveen.n.rao@linux.vnet.ibm.com
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Date:   Mon, 24 Feb 2020 18:02:10 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In order to avoid Oopses, use probe_address() to read the
instruction at the address where the trap happened.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/kprobes.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 84567406b53d..a35320b79e16 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -276,14 +276,18 @@ int kprobe_handler(struct pt_regs *regs)
 
 	p = get_kprobe(addr);
 	if (!p) {
-		if (*addr != BREAKPOINT_INSTRUCTION) {
+		unsigned int instr;
+
+		if (probe_kernel_address(addr, instr))
+			goto no_kprobe;
+
+		if (instr != BREAKPOINT_INSTRUCTION) {
 			/*
 			 * PowerPC has multiple variants of the "trap"
 			 * instruction. If the current instruction is a
 			 * trap variant, it could belong to someone else
 			 */
-			kprobe_opcode_t cur_insn = *addr;
-			if (is_trap(cur_insn))
+			if (is_trap(instr))
 				goto no_kprobe;
 			/*
 			 * The breakpoint instruction was removed right
-- 
2.25.0