[PATCH] Fix range check in do_tunable_update_val

[Siddhesh Poyarekar]

On Wednesday 27 September 2017 12:08 AM, Alexey Makhalov wrote:
> Current implementation of tunables does not set arena_max and arena_test
> values. Any value provided by glibc.malloc.arena_max and
> glibc.malloc.arena_test parameters is ignored.
> 
> These tunables have minval value set to 1 (see elf/dl-tunables.list file)
> and undefined maxval value. In that case default value (which is 0. see
> scripts/gen-tunables.awk) is being used to set maxval.
> 
> For instance, generated tunable_list[] entry for arena_max is:
> (gdb) p *cur
> $1 = {name = 0x7ffff7df6217 "glibc.malloc.arena_max",
>  type = {type_code = TUNABLE_TYPE_SIZE_T, min = 1, max = 0},
>   val = {numval = 0, strval = 0x0}, initialized = false,
>    security_level = TUNABLE_SECLEVEL_SXID_IGNORE,
>     env_alias = 0x7ffff7df622e "MALLOC_ARENA_MAX"}
> 
> As a result, any value of glibc.malloc.arena_max is ignored by
> TUNABLE_SET_VAL_IF_VALID_RANGE macro
>   __type min = (__cur)->type.min;                    <- initialized to 1
>   __type max = (__cur)->type.max;                    <- initialized to 0!
>   if (min == max)                                    <- false
>     {
>       min = __default_min;
>       max = __default_max;
>     }
>   if ((__type) (__val) >= min && (__type) (val) <= max)  <- false
>     {
>       (__cur)->val.numval = val;
>       (__cur)->initialized = true;
>     }
> 
> Assigning correct min/max values at a build time fixes a problem.
> Plus, a bit of optimization: Setting of default min/max values for the
> given type at a run time might be eliminated.

Thanks for the patch.  Can you please clarify the status of your
copyright assignment (and Carlos verify it please)?  I don't have access
to the copyright assignment list, so once that question is cleared, I'll
test and merge this patch.

Siddhesh