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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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