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    Subject[PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to refcount_t
    Date
    refcount_t type and corresponding API should be
    used instead of atomic_t when the variable is used as
    a reference counter. This allows to avoid accidental
    refcounter overflows that might lead to use-after-free
    situations.

    Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
    Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
    Signed-off-by: Kees Cook <keescook@chromium.org>
    Signed-off-by: David Windsor <dwindsor@gmail.com>
    ---
    tools/perf/util/comm.c | 13 +++++--------
    1 file changed, 5 insertions(+), 8 deletions(-)

    diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
    index 21b7ff3..0fd3d70 100644
    --- a/tools/perf/util/comm.c
    +++ b/tools/perf/util/comm.c
    @@ -2,12 +2,12 @@
    #include "util.h"
    #include <stdlib.h>
    #include <stdio.h>
    -#include <linux/atomic.h>
    +#include <linux/refcount.h>

    struct comm_str {
    char *str;
    struct rb_node rb_node;
    - atomic_t refcnt;
    + refcount_t refcnt;
    };

    /* Should perhaps be moved to struct machine */
    @@ -16,13 +16,13 @@ static struct rb_root comm_str_root;
    static struct comm_str *comm_str__get(struct comm_str *cs)
    {
    if (cs)
    - atomic_inc(&cs->refcnt);
    + refcount_inc(&cs->refcnt);
    return cs;
    }

    static void comm_str__put(struct comm_str *cs)
    {
    - if (cs && atomic_dec_and_test(&cs->refcnt)) {
    + if (cs && refcount_dec_and_test(&cs->refcnt)) {
    rb_erase(&cs->rb_node, &comm_str_root);
    zfree(&cs->str);
    free(cs);
    @@ -43,7 +43,7 @@ static struct comm_str *comm_str__alloc(const char *str)
    return NULL;
    }

    - atomic_set(&cs->refcnt, 0);
    + refcount_set(&cs->refcnt, 1);

    return cs;
    }
    @@ -95,8 +95,6 @@ struct comm *comm__new(const char *str, u64 timestamp, bool exec)
    return NULL;
    }

    - comm_str__get(comm->comm_str);
    -
    return comm;
    }

    @@ -108,7 +106,6 @@ int comm__override(struct comm *comm, const char *str, u64 timestamp, bool exec)
    if (!new)
    return -ENOMEM;

    - comm_str__get(new);
    comm_str__put(old);
    comm->comm_str = new;
    comm->start = timestamp;
    --
    2.7.4
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