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>

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 3f084a0ca7229d1d444226e91d5fc930e03403a2..0dc24e6cdd1e84aa2ba54b28cdb794bf63836186 100644 (file)
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -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);
 

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 3e7c6e5a08ffde197c192ab57f3bb38aac590969..b121037739e43e4a6ab6cf447bc5b70b58636b89 100644 (file)
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -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);