kprobes/x86: Set kprobes pages read-only

[ 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>

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 808ee7f566f882cb84a4ef79b7faefe0ef4e1fae..b8d3f1b60331e0bf8097fc2e2716c5e567aabb88 100644 (file)
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -409,6 +409,8 @@ static int arch_copy_kprobe(struct kprobe *p)
 {
        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)
@@ -423,6 +425,8 @@ static int arch_copy_kprobe(struct kprobe *p)
        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);
 

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index dc20da1c78f09588ec8462217b8b7b818f9c75c5..fa671b90c37457db89e7644cf3f62150b01a0d9d 100644 (file)
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -371,6 +371,7 @@ 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);
@@ -393,6 +394,8 @@ 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);