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Subject[PATCH 11/18] vchecker: consistently exclude vchecker's stacktrace
Date
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Since there is a different callpath even in the vchecker, static skip
value doesn't always exclude vchecker's stacktrace. Fix it through
checking stacktrace dynamically.

v2: skip two depth of stack at default, it's safe!

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
mm/kasan/vchecker.c | 41 +++++++++++++++++++++++++----------------
1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/mm/kasan/vchecker.c b/mm/kasan/vchecker.c
index df480d5..dc3a9a7 100644
--- a/mm/kasan/vchecker.c
+++ b/mm/kasan/vchecker.c
@@ -23,6 +23,7 @@
#include "kasan.h"

#define VCHECKER_STACK_DEPTH (16)
+#define VCHECKER_SKIP_DEPTH (2)

struct vchecker {
bool enabled;
@@ -48,7 +49,7 @@ struct vchecker_type {
void (*show)(struct kmem_cache *s, struct seq_file *f,
struct vchecker_cb *cb, void *object, bool verbose);
bool (*check)(struct kmem_cache *s, struct vchecker_cb *cb,
- void *object, bool write,
+ void *object, bool write, unsigned long ret_ip,
unsigned long begin, unsigned long end);
};

@@ -276,7 +277,7 @@ bool vchecker_check(unsigned long addr, size_t size,
continue;

checked = true;
- if (cb->type->check(s, cb, object, write, begin, end))
+ if (cb->type->check(s, cb, object, write, ret_ip, begin, end))
continue;

vchecker_report(addr, size, write, ret_ip, s, cb, object);
@@ -292,14 +293,29 @@ bool vchecker_check(unsigned long addr, size_t size,
return vchecker_poisoned((void *)addr, size);
}

-static noinline depot_stack_handle_t save_stack(int skip, bool *is_new)
+static void filter_vchecker_stacks(struct stack_trace *trace,
+ unsigned long ret_ip)
+{
+ int i;
+
+ for (i = 0; i < trace->nr_entries; i++) {
+ if (trace->entries[i] == ret_ip) {
+ trace->entries = &trace->entries[i];
+ trace->nr_entries -= i;
+ break;
+ }
+ }
+}
+
+static noinline depot_stack_handle_t save_stack(unsigned long ret_ip,
+ bool *is_new)
{
unsigned long entries[VCHECKER_STACK_DEPTH];
struct stack_trace trace = {
.nr_entries = 0,
.entries = entries,
.max_entries = VCHECKER_STACK_DEPTH,
- .skip = skip,
+ .skip = VCHECKER_SKIP_DEPTH,
};
depot_stack_handle_t handle;

@@ -311,6 +327,7 @@ static noinline depot_stack_handle_t save_stack(int skip, bool *is_new)
if (trace.nr_entries == 0)
return 0;

+ filter_vchecker_stacks(&trace, ret_ip);
handle = depot_save_stack(NULL, &trace, __GFP_ATOMIC, is_new);
WARN_ON(!handle);

@@ -542,7 +559,7 @@ static void show_value(struct kmem_cache *s, struct seq_file *f,
}

static bool check_value(struct kmem_cache *s, struct vchecker_cb *cb,
- void *object, bool write,
+ void *object, bool write, unsigned long ret_ip,
unsigned long begin, unsigned long end)
{
struct vchecker_value_arg *arg;
@@ -553,7 +570,7 @@ static bool check_value(struct kmem_cache *s, struct vchecker_cb *cb,
if (!write)
goto check;

- handle = save_stack(0, NULL);
+ handle = save_stack(ret_ip, NULL);
if (!handle) {
pr_err("VCHECKER: %s: fail at addr %p\n", __func__, object);
dump_stack();
@@ -679,16 +696,8 @@ static void show_callstack(struct kmem_cache *s, struct seq_file *f,
}
}

-/*
- * number of stacks to skip (at least).
- *
- * __asan_loadX -> vchecker_check -> cb->check() -> save_stack
- * -> save_stack_trace
- */
-#define STACK_SKIP 5
-
static bool check_callstack(struct kmem_cache *s, struct vchecker_cb *cb,
- void *object, bool write,
+ void *object, bool write, unsigned long ret_ip,
unsigned long begin, unsigned long end)
{
u32 handle;
@@ -696,7 +705,7 @@ static bool check_callstack(struct kmem_cache *s, struct vchecker_cb *cb,
struct vchecker_callstack_arg *arg = cb->arg;
int idx;

- handle = save_stack(STACK_SKIP, &is_new);
+ handle = save_stack(ret_ip, &is_new);
if (!is_new)
return true;

--
2.7.4
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