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

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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: d0381c81c2 ("kprobes/x86: Set kprobes pages read-only")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2017-05-25 19:38:17 +09:00 committed by Steven Rostedt (VMware)
parent f9797c2f20
commit c93f5cf571
2 changed files with 10 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/x86/kernel/kprobes/core.c
View File

@ -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;

2
kernel/kprobes.c
View File

@ -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);
}