Commit d0381c81 authored Mar 29, 2017 by Masami Hiramatsu Committed by Ingo Molnar Apr 12, 2017

kprobes/x86: Set kprobes pages read-only



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>

parent 490154bc

arch/x86/kernel/kprobes/core.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -419,6 +419,8 @@ static int arch_copy_kprobe(struct kprobe *p)
		{
		int len;

		set_memory_rw((unsigned long)p->ainsn.insn & PAGE_MASK, 1);

		/* Copy an instruction with recovering if other optprobe modifies it.*/
		len = __copy_instruction(p->ainsn.insn, p->addr);
		if (!len)
		@@ -430,6 +432,8 @@ static int arch_copy_kprobe(struct kprobe *p)
		*/
		prepare_boost(p, len);

		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);

arch/x86/kernel/kprobes/opt.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -350,6 +350,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
		}

		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);
		@@ -372,6 +373,8 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
		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);