[PATCH] kasan: better invalid/double-free report header

[andrey.k...@linux.dev]

From: Andrey Konovalov <andre...@google.com>

Update the report header for invalid- and double-free bugs to contain
the address being freed:

BUG: KASAN: invalid-free in kfree+0x280/0x2a8
Free of addr ffff00000beac001 by task kunit_try_catch/99

Signed-off-by: Andrey Konovalov <andre...@google.com>
---
mm/kasan/report.c | 23 ++++++++++++++++-------
mm/kasan/report_generic.c | 3 ++-
mm/kasan/report_tags.c | 2 +-
3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 39e8e5a80b82..df3602062bfd 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -175,17 +175,14 @@ 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: invalid-free in %pS\n", (void *)info->ip);
- return;
- }
+ pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);

- if (info->type == KASAN_REPORT_DOUBLE_FREE) {
- pr_err("BUG: KASAN: double-free in %pS\n", (void *)info->ip);
+ if (info->type != KASAN_REPORT_ACCESS) {
+ pr_err("Free of addr %px by task %s/%d\n",
+ info->access_addr, current->comm, task_pid_nr(current));
return;
}

- pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
if (info->access_size)
pr_err("%s of size %zu at addr %px by task %s/%d\n",
info->is_write ? "Write" : "Read", info->access_size,
@@ -420,6 +417,18 @@ static void complete_report_info(struct kasan_report_info *info)
} else
info->cache = info->object = NULL;

+ switch (info->type) {
+ case KASAN_REPORT_INVALID_FREE:
+ info->bug_type = "invalid-free";
+ break;
+ case KASAN_REPORT_DOUBLE_FREE:
+ info->bug_type = "double-free";
+ break;
+ default:
+ /* bug_type filled in by kasan_complete_mode_report_info. */
+ break;
+ }
+
/* Fill in mode-specific report info fields. */
kasan_complete_mode_report_info(info);
}
diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
index 087c1d8c8145..043c94b04605 100644
--- a/mm/kasan/report_generic.c
+++ b/mm/kasan/report_generic.c
@@ -132,7 +132,8 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
struct kasan_alloc_meta *alloc_meta;
struct kasan_free_meta *free_meta;

- info->bug_type = get_bug_type(info);
+ if (!info->bug_type)
+ info->bug_type = get_bug_type(info);

if (!info->cache || !info->object)
return;
diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
index d3510424d29b..ecede06ef374 100644
--- a/mm/kasan/report_tags.c
+++ b/mm/kasan/report_tags.c
@@ -37,7 +37,7 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
bool is_free;
bool alloc_found = false, free_found = false;

- if (!info->cache || !info->object) {
+ if ((!info->cache || !info->object) && !info->bug_type) {
info->bug_type = get_common_bug_type(info);
return;
}
--
2.25.1

[Andrey Konovalov]

On Sun, Sep 11, 2022 at 1:25 AM <andrey.k...@linux.dev> wrote:
>
> From: Andrey Konovalov <andre...@google.com>
>
> Update the report header for invalid- and double-free bugs to contain
> the address being freed:
>
> BUG: KASAN: invalid-free in kfree+0x280/0x2a8
> Free of addr ffff00000beac001 by task kunit_try_catch/99
>
> Signed-off-by: Andrey Konovalov <andre...@google.com>

Forgot to mention: this goes on top of the "kasan: switch tag-based
modes to stack ring from per-object metadata" series.

[Marco Elver]

On Sun, 11 Sept 2022 at 01:25, <andrey.k...@linux.dev> wrote:
>
> From: Andrey Konovalov <andre...@google.com>
>
> Update the report header for invalid- and double-free bugs to contain
> the address being freed:
>
> BUG: KASAN: invalid-free in kfree+0x280/0x2a8
> Free of addr ffff00000beac001 by task kunit_try_catch/99

It wouldn't hurt showing a full before vs. after report here in the
commit message for ease of reviewing.

> Signed-off-by: Andrey Konovalov <andre...@google.com>

Reviewed-by: Marco Elver <el...@google.com>