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: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index 5201d1770700a8fb3dbda9374e0ac40b4614a946..a4604cceae59416fee51e1affa15c508404393d4 100644 (file)
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -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);
 
        /*

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 33cc3b0e017ec840bb33f1741ed141250680ff13..82a23b23ff93fcc991ff61c8fded5e4d0fec293a 100644 (file)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -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;

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 64a74f334c4562e73fe5bfeef8ddaf511075b1e2..214d85035f998c4727ff5ac966684d4695b6b690 100644 (file)
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -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);
 }

diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
index 8af15e87d3bc57f75fad6ff586c5103f9ad222a9..573c51d20d09462b8ac366741b0c177b52e44ac5 100644 (file)
--- a/mm/kasan/tags_report.c
+++ b/mm/kasan/tags_report.c
@@ -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);
+}