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

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>

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 5b2bbfbb371284942b2ce95a3b2495eb9ecc8981..6b877807598b9028527a2357fef630431021c383 100644 (file)
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -52,6 +52,7 @@
 #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>
@@ -417,6 +418,14 @@ static void prepare_boost(struct kprobe *p, struct insn *insn)
        }
 }
 
+/* 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)
 {
        struct insn insn;

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2d2d3a568e4e8b3aeedb16711c90e660f698d6cf..adfe3b4cfe05a101bcee0da8e72db6fe6a10cf72 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -122,7 +122,7 @@ 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);
 }