Patch "kprobes/x86: Set kprobes pages read-only" has been added to the 3.18-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    kprobes/x86: Set kprobes pages read-only

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kprobes-x86-set-kprobes-pages-read-only.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Mar 19 10:11:52 CET 2018
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Wed, 29 Mar 2017 14:02:46 +0900
Subject: kprobes/x86: Set kprobes pages read-only

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+0x7a9/0xa20
  x86/mm: Found insecure W+X mapping at address ffffffffa0000000/0xffffffffa0000000

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.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/kprobes/core.c |    4 ++++
 arch/x86/kernel/kprobes/opt.c  |    3 +++
 2 files changed, 7 insertions(+)

--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -378,6 +378,8 @@ static int arch_copy_kprobe(struct kprob
 {
 	int ret;
 
+	set_memory_rw((unsigned long)p->ainsn.insn & PAGE_MASK, 1);
+
 	/* Copy an instruction with recovering if other optprobe modifies it.*/
 	ret = __copy_instruction(p->ainsn.insn, p->addr);
 	if (!ret)
@@ -392,6 +394,8 @@ static int arch_copy_kprobe(struct kprob
 	else
 		p->ainsn.boostable = -1;
 
+	set_memory_ro((unsigned long)p->ainsn.insn & PAGE_MASK, 1);
+
 	/* Check whether the instruction modifies Interrupt Flag or not */
 	p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn);
 
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -344,6 +344,7 @@ int arch_prepare_optimized_kprobe(struct
 	}
 
 	buf = (u8 *)op->optinsn.insn;
+	set_memory_rw((unsigned long)buf & PAGE_MASK, 1);
 
 	/* Copy instructions into the out-of-line buffer */
 	ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
@@ -366,6 +367,8 @@ int arch_prepare_optimized_kprobe(struct
 	synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
 			   (u8 *)op->kp.addr + op->optinsn.size);
 
+	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);


Patches currently in stable-queue which might be from mhiramat@kernel.org are

queue-3.18/perf-session-don-t-rely-on-evlist-in-pipe-mode.patch
queue-3.18/kprobes-x86-set-kprobes-pages-read-only.patch
queue-3.18/kprobes-x86-fix-kprobe-booster-not-to-boost-far-call-instructions.patch
queue-3.18/perf-inject-copy-events-when-reordering-events-in-pipe-mode.patch