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

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 <[email protected]> know about it.

From: Masami Hiramatsu <[email protected]>
Date: Wed, 29 Mar 2017 14:02:46 +0900
Subject: kprobes/x86: Set kprobes pages read-only

From: Masami Hiramatsu <[email protected]>

[ 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

---
 arch/x86/kernel/kprobes/core.c |    4 ++++
 arch/x86/kernel/kprobes/opt.c  |    3 +++
 2 files changed, 7 insertions(+)

@@ -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);
 

@@ -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 [email protected] 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