Re: [Qemu-devel] [PATCH v3] make check-unit: use after free in test-opts-visitor

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

PINGING...

On 05/08/2019 20:03, Andrey Shinkevich wrote:
> In the struct OptsVisitor, the 'repeated_opts' member points to a list
> in the 'unprocessed_opts' hash table after the list has been destroyed.
> A subsequent call to visit_type_int() references the deleted list.
> It results in use-after-free issue reproduced by running the test case
> under the Valgrind: valgrind tests/test-opts-visitor.
> A new mode ListMode::LM_TRAVERSED is declared to mark the list
> traversal completed.
> 
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
> 
> v3:
>   01: The comment of the patch header was amended.
>   02: The change in spacing of 'ListMode' comment blocks was rolled back.
>   03: The 'repeated_opts' in opts_end_list() is now reset unconditionally
>       as it was.
>   04: The 'name' in the error_setg() was removed as the pointer to the list
>       name can be null (suggested by Markus).
> 
>   qapi/opts-visitor.c | 26 ++++++++++++++++++++++----
>   1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
> index 324b197..5fe0276 100644
> --- a/qapi/opts-visitor.c
> +++ b/qapi/opts-visitor.c
> @@ -24,7 +24,8 @@ enum ListMode
>   {
>       LM_NONE,             /* not traversing a list of repeated options */
>   
> -    LM_IN_PROGRESS,      /* opts_next_list() ready to be called.
> +    LM_IN_PROGRESS,      /*
> +                          * opts_next_list() ready to be called.
>                             *
>                             * Generating the next list link will consume the most
>                             * recently parsed QemuOpt instance of the repeated
> @@ -36,7 +37,8 @@ enum ListMode
>                             * LM_UNSIGNED_INTERVAL.
>                             */
>   
> -    LM_SIGNED_INTERVAL,  /* opts_next_list() has been called.
> +    LM_SIGNED_INTERVAL,  /*
> +                          * opts_next_list() has been called.
>                             *
>                             * Generating the next list link will consume the most
>                             * recently stored element from the signed interval,
> @@ -48,7 +50,14 @@ enum ListMode
>                             * next element of the signed interval.
>                             */
>   
> -    LM_UNSIGNED_INTERVAL /* Same as above, only for an unsigned interval. */
> +    LM_UNSIGNED_INTERVAL, /* Same as above, only for an unsigned interval. */
> +
> +    LM_TRAVERSED          /*
> +                           * opts_next_list() has been called.
> +                           *
> +                           * No more QemuOpt instance in the list.
> +                           * The traversal has been completed.
> +                           */
>   };
>   
>   typedef enum ListMode ListMode;
> @@ -238,6 +247,8 @@ opts_next_list(Visitor *v, GenericList *tail, size_t size)
>       OptsVisitor *ov = to_ov(v);
>   
>       switch (ov->list_mode) {
> +    case LM_TRAVERSED:
> +        return NULL;
>       case LM_SIGNED_INTERVAL:
>       case LM_UNSIGNED_INTERVAL:
>           if (ov->list_mode == LM_SIGNED_INTERVAL) {
> @@ -258,6 +269,8 @@ opts_next_list(Visitor *v, GenericList *tail, size_t size)
>           opt = g_queue_pop_head(ov->repeated_opts);
>           if (g_queue_is_empty(ov->repeated_opts)) {
>               g_hash_table_remove(ov->unprocessed_opts, opt->name);
> +            ov->repeated_opts = NULL;
> +            ov->list_mode = LM_TRAVERSED;
>               return NULL;
>           }
>           break;
> @@ -289,7 +302,8 @@ opts_end_list(Visitor *v, void **obj)
>   
>       assert(ov->list_mode == LM_IN_PROGRESS ||
>              ov->list_mode == LM_SIGNED_INTERVAL ||
> -           ov->list_mode == LM_UNSIGNED_INTERVAL);
> +           ov->list_mode == LM_UNSIGNED_INTERVAL ||
> +           ov->list_mode == LM_TRAVERSED);
>       ov->repeated_opts = NULL;
>       ov->list_mode = LM_NONE;
>   }
> @@ -306,6 +320,10 @@ lookup_scalar(const OptsVisitor *ov, const char *name, Error **errp)
>           list = lookup_distinct(ov, name, errp);
>           return list ? g_queue_peek_tail(list) : NULL;
>       }
> +    if (ov->list_mode == LM_TRAVERSED) {
> +        error_setg(errp, "Fewer list elements than expected");
> +        return NULL;
> +    }
>       assert(ov->list_mode == LM_IN_PROGRESS);
>       return g_queue_peek_head(ov->repeated_opts);
>   }
> 

-- 
With the best regards,
Andrey Shinkevich