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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Masami Hiramatsu <mhiramat@kernel.org>,
        Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        Borislav Petkov <bp@alien8.de>,
        Brian Gerst <brgerst@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ye Xiaolong <xiaolong.ye@intel.com>,
        Ingo Molnar <mingo@kernel.org>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.4 081/115] kprobes/x86: Set kprobes pages
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Thread-Topic: [PATCH AUTOSEL for 4.4 081/115] kprobes/x86: Set kprobes pages
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Thread-Index: AQHTsz9kUOnWfuJNXkO6DLcgMcusoA==
Date:   Sat, 3 Mar 2018 22:31:38 +0000
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From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit d0381c81c2f782fa2131178d11e0cfb23d50d631 ]

Set the pages which is used for kprobes' singlestep buffer
and optprobe's trampoline instruction buffer to readonly.
This can prevent unexpected (or unintended) instruction
modification.

This also passes rodata_test as below.

Without this patch, rodata_test shows a warning:

  WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:235 note_page+0x7=
a9/0xa20
  x86/mm: Found insecure W+X mapping at address ffffffffa0000000/0xffffffff=
a0000000

With this fix, no W+X pages are found:

  x86/mm: Checked W+X mappings: passed, no W+X pages found.
  rodata_test: all tests were successful

Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.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/149076375592.22469.14174394514338612247.stgi=
t@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/x86/kernel/kprobes/core.c | 4 ++++
 arch/x86/kernel/kprobes/opt.c  | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.=
c
index 5d11d01f75de..565e24e9ddf2 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -406,6 +406,8 @@ static int arch_copy_kprobe(struct kprobe *p)
 {
 	int ret;
=20
+	set_memory_rw((unsigned long)p->ainsn.insn & PAGE_MASK, 1);
+
 	/* Copy an instruction with recovering if other optprobe modifies it.*/
 	ret =3D __copy_instruction(p->ainsn.insn, p->addr);
 	if (!ret)
@@ -420,6 +422,8 @@ static int arch_copy_kprobe(struct kprobe *p)
 	else
 		p->ainsn.boostable =3D -1;
=20
+	set_memory_ro((unsigned long)p->ainsn.insn & PAGE_MASK, 1);
+
 	/* Check whether the instruction modifies Interrupt Flag or not */
 	p->ainsn.if_modifier =3D is_IF_modifier(p->ainsn.insn);
=20
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index ea8e2b846101..7aba9d6475a5 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -370,6 +370,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kpro=
be *op,
 	}
=20
 	buf =3D (u8 *)op->optinsn.insn;
+	set_memory_rw((unsigned long)buf & PAGE_MASK, 1);
=20
 	/* Copy instructions into the out-of-line buffer */
 	ret =3D copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
@@ -392,6 +393,8 @@ int arch_prepare_optimized_kprobe(struct optimized_kpro=
be *op,
 	synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
 			   (u8 *)op->kp.addr + op->optinsn.size);
=20
+	set_memory_ro((unsigned long)buf & PAGE_MASK, 1);
+
 	flush_icache_range((unsigned long) buf,
 			   (unsigned long) buf + TMPL_END_IDX +
 			   op->optinsn.size + RELATIVEJUMP_SIZE);
--=20
2.14.1