Re: [PATCH][next] media: venus: hfi_cmds: Replace one-element array with flex-array member and use __counted_by

[Sergey Senozhatsky]

On (23/10/09 12:52), Kees Cook wrote:
> On Mon, Oct 09, 2023 at 12:42:05PM -0600, Gustavo A. R. Silva wrote:
> > Array `data` in `struct hfi_sfr` is being used as a fake flexible array
> > at run-time:
> > 
> > drivers/media/platform/qcom/venus/hfi_venus.c:
> > 1033         p = memchr(sfr->data, '\0', sfr->buf_size);
> > 1034         /*
> > 1035          * SFR isn't guaranteed to be NULL terminated since SYS_ERROR indicates
> > 1036          * that Venus is in the process of crashing.
> > 1037          */
> > 1038         if (!p)
> > 1039                 sfr->data[sfr->buf_size - 1] = '\0';
> > 1040
> > 1041         dev_err_ratelimited(dev, "SFR message from FW: %s\n", sfr->data);
> > 
> > Fake flexible arrays are deprecated, and should be replaced by
> > flexible-array members. So, replace one-element array with a
> > flexible-array member in `struct hfi_sfr`.
> > 
> > While there, also annotate array `data` with __counted_by() to prepare
> > for the coming implementation by GCC and Clang of the __counted_by
> > attribute. Flexible array members annotated with __counted_by can have
> > their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> > array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> > functions).
> > 
> > This results in no differences in binary output.
> 
> Thanks for checking!

Sorry for shameless plug, a quick question: has any compiler implemented
support for counted_by() at this point?