Commit 3de0de75 authored by Kuan-Ying Lee's avatar Kuan-Ying Lee Committed by Andrew Morton
Browse files

kasan: separate double free case from invalid free 

Currently, KASAN describes all invalid-free/double-free bugs as
"double-free or invalid-free".  This is ambiguous.

KASAN should report "double-free" when a double-free is a more likely
cause (the address points to the start of an object) and report
"invalid-free" otherwise [1].

[1] https://bugzilla.kernel.org/show_bug.cgi?id=212193

Link: https://lkml.kernel.org/r/20220615062219.22618-1-Kuan-Ying.Lee@mediatek.com


Signed-off-by: default avatarKuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Yee Lee <yee.lee@mediatek.com>
Cc: Andrew Yang <andrew.yang@mediatek.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent cb55b838

mm/kasan/common.c

+4 −4
Original line number Diff line number Diff line
@@ -343,7 +343,7 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, 


	if (unlikely(nearest_obj(cache, virt_to_slab(object), object) !=

	    object)) {

		kasan_report_invalid_free(tagged_object, ip);

		kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE);

		return true;

	}
@@ -352,7 +352,7 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, 
		return false;



	if (!kasan_byte_accessible(tagged_object)) {

		kasan_report_invalid_free(tagged_object, ip);

		kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE);

		return true;

	}
@@ -377,12 +377,12 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object, 
static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip)

{

	if (ptr != page_address(virt_to_head_page(ptr))) {

		kasan_report_invalid_free(ptr, ip);

		kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);

		return true;

	}



	if (!kasan_byte_accessible(ptr)) {

		kasan_report_invalid_free(ptr, ip);

		kasan_report_invalid_free(ptr, ip, KASAN_REPORT_DOUBLE_FREE);

		return true;

	}

mm/kasan/kasan.h

+2 −1
Original line number Diff line number Diff line
@@ -125,6 +125,7 @@ static inline bool kasan_sync_fault_possible(void) 
enum kasan_report_type {

	KASAN_REPORT_ACCESS,

	KASAN_REPORT_INVALID_FREE,

	KASAN_REPORT_DOUBLE_FREE,

};



struct kasan_report_info {
@@ -277,7 +278,7 @@ static inline void kasan_print_address_stack_frame(const void *addr) { } 


bool kasan_report(unsigned long addr, size_t size,

		bool is_write, unsigned long ip);

void kasan_report_invalid_free(void *object, unsigned long ip);

void kasan_report_invalid_free(void *object, unsigned long ip, enum kasan_report_type type);



struct page *kasan_addr_to_page(const void *addr);

struct slab *kasan_addr_to_slab(const void *addr);

mm/kasan/report.c

+8 −4
Original line number Diff line number Diff line
@@ -176,8 +176,12 @@ static void end_report(unsigned long *flags, void *addr) 
static void print_error_description(struct kasan_report_info *info)

{

	if (info->type == KASAN_REPORT_INVALID_FREE) {

		pr_err("BUG: KASAN: double-free or invalid-free in %pS\n",

		       (void *)info->ip);

		pr_err("BUG: KASAN: invalid-free in %pS\n", (void *)info->ip);

		return;

	}



	if (info->type == KASAN_REPORT_DOUBLE_FREE) {

		pr_err("BUG: KASAN: double-free in %pS\n", (void *)info->ip);

		return;

	}
@@ -433,7 +437,7 @@ static void print_report(struct kasan_report_info *info) 
	}

}



void kasan_report_invalid_free(void *ptr, unsigned long ip)

void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)

{

	unsigned long flags;

	struct kasan_report_info info;
@@ -448,7 +452,7 @@ void kasan_report_invalid_free(void *ptr, unsigned long ip) 


	start_report(&flags, true);



	info.type = KASAN_REPORT_INVALID_FREE;

	info.type = type;

	info.access_addr = ptr;

	info.first_bad_addr = kasan_reset_tag(ptr);

	info.access_size = 0;