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

kprobes/x86: Fix to set RWX bits correctly before releasing trampoline

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kprobes-x86-fix-to-set-rwx-bits-correctly-before-releasing-trampoline.patch and it can be found in the queue-4.9 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 c93f5cf571e7795f97d49ef51b766cf25e328545 Mon Sep 17 00:00:00 2001

From: Masami Hiramatsu mhiramat@kernel.org Date: Thu, 25 May 2017 19:38:17 +0900 Subject: kprobes/x86: Fix to set RWX bits correctly before releasing trampoline

From: Masami Hiramatsu mhiramat@kernel.org

commit c93f5cf571e7795f97d49ef51b766cf25e328545 upstream.

Fix kprobes to set(recover) RWX bits correctly on trampoline buffer before releasing it. Releasing readonly page to module_memfree() crash the kernel.

Without this fix, if kprobes user register a bunch of kprobes in function body (since kprobes on function entry usually use ftrace) and unregister it, kernel hits a BUG and crash.

Link: http://lkml.kernel.org/r/149570868652.3518.14120169373590420503.stgit@devbox

Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Fixes: d0381c81c2f7 ("kprobes/x86: Set kprobes pages read-only") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Cc: Ben Hutchings ben.hutchings@codethink.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/kernel/kprobes/core.c | 9 +++++++++ kernel/kprobes.c | 2 +- 2 files changed, 10 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -51,6 +51,7 @@ #include <linux/ftrace.h> #include <linux/frame.h> #include <linux/kasan.h> +#include <linux/moduleloader.h>

#include <asm/text-patching.h> #include <asm/cacheflush.h> @@ -405,6 +406,14 @@ int __copy_instruction(u8 *dest, u8 *src return length; }

+/* Recover page to RW mode before releasing it */ +void free_insn_page(void *page) +{ + set_memory_nx((unsigned long)page & PAGE_MASK, 1); + set_memory_rw((unsigned long)page & PAGE_MASK, 1); + module_memfree(page); +} + static int arch_copy_kprobe(struct kprobe *p) { int ret; --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -125,7 +125,7 @@ static void *alloc_insn_page(void) return module_alloc(PAGE_SIZE); }

-static void free_insn_page(void *page) +void __weak free_insn_page(void *page) { module_memfree(page); }

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

queue-4.9/kprobes-x86-fix-to-set-rwx-bits-correctly-before-releasing-trampoline.patch