4.4-stable review patch. If anyone has any objections, please let me know.
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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 @@ -49,6 +49,7 @@ #include <linux/kdebug.h> #include <linux/kallsyms.h> #include <linux/ftrace.h> +#include <linux/moduleloader.h>
#include <asm/cacheflush.h> #include <asm/desc.h> @@ -402,6 +403,14 @@ 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); }