Commit 57b78a62 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

x86/uaccess, kasan: Fix KASAN vs SMAP 



KASAN inserts extra code for every LOAD/STORE emitted by te compiler.
Much of this code is simple and safe to run with AC=1, however the
kasan_report() function, called on error, is most certainly not safe
to call with AC=1.

Therefore wrap kasan_report() in user_access_{save,restore}; which for
x86 SMAP, saves/restores EFLAGS and clears AC before calling the real
function.

Also ensure all the functions are without __fentry__ hook. The
function tracer is also not safe.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Vyukov <dvyukov@google.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>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a936af8e

mm/kasan/Makefile

+3 −0
Original line number Diff line number Diff line
@@ -2,11 +2,13 @@ 
KASAN_SANITIZE := n

UBSAN_SANITIZE_common.o := n

UBSAN_SANITIZE_generic.o := n

UBSAN_SANITIZE_generic_report.o := n

UBSAN_SANITIZE_tags.o := n

KCOV_INSTRUMENT := n



CFLAGS_REMOVE_common.o = -pg

CFLAGS_REMOVE_generic.o = -pg

CFLAGS_REMOVE_generic_report.o = -pg

CFLAGS_REMOVE_tags.o = -pg



# Function splitter causes unnecessary splits in __asan_load1/__asan_store1
@@ -14,6 +16,7 @@ CFLAGS_REMOVE_tags.o = -pg 


CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)

CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)

CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)

CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)



obj-$(CONFIG_KASAN) := common.o init.o report.o

mm/kasan/common.c

+10 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
#include <linux/types.h>

#include <linux/vmalloc.h>

#include <linux/bug.h>

#include <linux/uaccess.h>



#include "kasan.h"

#include "../slab.h"
@@ -614,6 +615,15 @@ void kasan_free_shadow(const struct vm_struct *vm) 
		vfree(kasan_mem_to_shadow(vm->addr));

}



extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);



void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)

{

	unsigned long flags = user_access_save();

	__kasan_report(addr, size, is_write, ip);

	user_access_restore(flags);

}



#ifdef CONFIG_MEMORY_HOTPLUG

static bool shadow_mapped(unsigned long addr)

{

mm/kasan/report.c

+1 −2
Original line number Diff line number Diff line
@@ -281,8 +281,7 @@ void kasan_report_invalid_free(void *object, unsigned long ip) 
	end_report(&flags);

}



void kasan_report(unsigned long addr, size_t size,

		bool is_write, unsigned long ip)

void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)

{

	struct kasan_access_info info;

	void *tagged_addr;

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