From ea1e34fc366b84e4449b37d86f2222935e29412d Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Wed, 29 Mar 2017 14:03:56 +0900
Subject: [PATCH] kprobes/x86: Use probe_kernel_read() instead of memcpy()

Use probe_kernel_read() for avoiding unexpected faults while
copying kernel text in __recover_probed_insn(),
__recover_optprobed_insn() and __copy_instruction().

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ye Xiaolong <xiaolong.ye@intel.com>
Link: http://lkml.kernel.org/r/149076382624.22469.10091613887942958518.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/kprobes/core.c | 12 +++++++++---
 arch/x86/kernel/kprobes/opt.c  |  5 ++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 0dc24e6..722f544 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -259,7 +259,10 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
 	 * Fortunately, we know that the original code is the ideal 5-byte
 	 * long NOP.
 	 */
-	memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+	if (probe_kernel_read(buf, (void *)addr,
+		MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
+		return 0UL;
+
 	if (faddr)
 		memcpy(buf, ideal_nops[NOP_ATOMIC5], 5);
 	else
@@ -271,7 +274,7 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
  * Recover the probed instruction at addr for further analysis.
  * Caller must lock kprobes by kprobe_mutex, or disable preemption
  * for preventing to release referencing kprobes.
- * Returns zero if the instruction can not get recovered.
+ * Returns zero if the instruction can not get recovered (or access failed).
  */
 unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
 {
@@ -365,7 +368,10 @@ int __copy_instruction(u8 *dest, u8 *src)
 	/* Another subsystem puts a breakpoint, failed to recover */
 	if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
 		return 0;
-	memcpy(dest, insn.kaddr, length);
+
+	/* This can access kernel text if given address is not recovered */
+	if (kernel_probe_read(dest, insn.kaddr, length))
+		return 0;
 
 #ifdef CONFIG_X86_64
 	/* Only x86_64 has RIP relative instructions */
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index b121037..5b52334 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -65,7 +65,10 @@ found:
 	 * overwritten by jump destination address. In this case, original
 	 * bytes must be recovered from op->optinsn.copied_insn buffer.
 	 */
-	memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+	if (probe_kernel_read(buf, (void *)addr,
+		MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
+		return 0UL;
+
 	if (addr == (unsigned long)kp->addr) {
 		buf[0] = kp->opcode;
 		memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
-- 
2.7.4