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Commit 121e8f81 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

kasan: add bug reporting routines for tag-based mode 

This commit adds rountines, that print tag-based KASAN error reports.
Those are quite similar to generic KASAN, the difference is:

1. The way tag-based KASAN finds the first bad shadow cell (with a
   mismatching tag). Tag-based KASAN compares memory tags from the shadow
   memory to the pointer tag.

2. Tag-based KASAN reports all bugs with the "KASAN: invalid-access"
   header.

Also simplify generic KASAN find_first_bad_addr.

Link: http://lkml.kernel.org/r/aee6897b1bd077732a315fd84c6b4f234dbfdfcb.1544099024.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 11cd3cd6

mm/kasan/generic_report.c

+5 −11
Original line number Diff line number Diff line
@@ -33,16 +33,13 @@ 
#include "kasan.h"

#include "../slab.h"



static const void *find_first_bad_addr(const void *addr, size_t size)

void *find_first_bad_addr(void *addr, size_t size)

{

	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);

	const void *first_bad_addr = addr;

	void *p = addr;



	while (!shadow_val && first_bad_addr < addr + size) {

		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;

		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);

	}

	return first_bad_addr;

	while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))

		p += KASAN_SHADOW_SCALE_SIZE;

	return p;

}



static const char *get_shadow_bug_type(struct kasan_access_info *info)
@@ -50,9 +47,6 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) 
	const char *bug_type = "unknown-crash";

	u8 *shadow_addr;



	info->first_bad_addr = find_first_bad_addr(info->access_addr,

						info->access_size);



	shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);



	/*

mm/kasan/kasan.h

+5 −0
Original line number Diff line number Diff line
@@ -119,6 +119,7 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value); 
void check_memory_region(unsigned long addr, size_t size, bool write,

				unsigned long ret_ip);



void *find_first_bad_addr(void *addr, size_t size);

const char *get_bug_type(struct kasan_access_info *info);



void kasan_report(unsigned long addr, size_t size,
@@ -139,10 +140,14 @@ static inline void quarantine_remove_cache(struct kmem_cache *cache) { } 


#ifdef CONFIG_KASAN_SW_TAGS



void print_tags(u8 addr_tag, const void *addr);



u8 random_tag(void);



#else



static inline void print_tags(u8 addr_tag, const void *addr) { }



static inline u8 random_tag(void)

{

	return 0;

mm/kasan/report.c

+31 −26
Original line number Diff line number Diff line
@@ -64,11 +64,10 @@ static int __init kasan_set_multi_shot(char *str) 
}

__setup("kasan_multi_shot", kasan_set_multi_shot);



static void print_error_description(struct kasan_access_info *info,

					const char *bug_type)

static void print_error_description(struct kasan_access_info *info)

{

	pr_err("BUG: KASAN: %s in %pS\n",

		bug_type, (void *)info->ip);

		get_bug_type(info), (void *)info->ip);

	pr_err("%s of size %zu at addr %px by task %s/%d\n",

		info->is_write ? "Write" : "Read", info->access_size,

		info->access_addr, current->comm, task_pid_nr(current));
@@ -272,6 +271,8 @@ void kasan_report_invalid_free(void *object, unsigned long ip) 


	start_report(&flags);

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

	print_tags(get_tag(object), reset_tag(object));

	object = reset_tag(object);

	pr_err("\n");

	print_address_description(object);

	pr_err("\n");
@@ -279,41 +280,45 @@ void kasan_report_invalid_free(void *object, unsigned long ip) 
	end_report(&flags);

}



static void kasan_report_error(struct kasan_access_info *info)

{

	unsigned long flags;



	start_report(&flags);



	print_error_description(info, get_bug_type(info));

	pr_err("\n");



	if (!addr_has_shadow(info->access_addr)) {

		dump_stack();

	} else {

		print_address_description((void *)info->access_addr);

		pr_err("\n");

		print_shadow_for_address(info->first_bad_addr);

	}



	end_report(&flags);

}



void kasan_report(unsigned long addr, size_t size,

		bool is_write, unsigned long ip)

{

	struct kasan_access_info info;

	void *tagged_addr;

	void *untagged_addr;

	unsigned long flags;



	if (likely(!report_enabled()))

		return;



	disable_trace_on_warning();



	info.access_addr = (void *)addr;

	info.first_bad_addr = (void *)addr;

	tagged_addr = (void *)addr;

	untagged_addr = reset_tag(tagged_addr);



	info.access_addr = tagged_addr;

	if (addr_has_shadow(untagged_addr))

		info.first_bad_addr = find_first_bad_addr(tagged_addr, size);

	else

		info.first_bad_addr = untagged_addr;

	info.access_size = size;

	info.is_write = is_write;

	info.ip = ip;



	kasan_report_error(&info);

	start_report(&flags);



	print_error_description(&info);

	if (addr_has_shadow(untagged_addr))

		print_tags(get_tag(tagged_addr), info.first_bad_addr);

	pr_err("\n");



	if (addr_has_shadow(untagged_addr)) {

		print_address_description(untagged_addr);

		pr_err("\n");

		print_shadow_for_address(info.first_bad_addr);

	} else {

		dump_stack();

	}



	end_report(&flags);

}

mm/kasan/tags_report.c

+18 −0
Original line number Diff line number Diff line
@@ -37,3 +37,21 @@ const char *get_bug_type(struct kasan_access_info *info) 
{

	return "invalid-access";

}



void *find_first_bad_addr(void *addr, size_t size)

{

	u8 tag = get_tag(addr);

	void *p = reset_tag(addr);

	void *end = p + size;



	while (p < end && tag == *(u8 *)kasan_mem_to_shadow(p))

		p += KASAN_SHADOW_SCALE_SIZE;

	return p;

}



void print_tags(u8 addr_tag, const void *addr)

{

	u8 *shadow = (u8 *)kasan_mem_to_shadow(addr);



	pr_err("Pointer tag: [%02x], memory tag: [%02x]\n", addr_tag, *shadow);

}