On Sat, Sep 23, 2023 at 07:09:19AM -0500, Alex Elder wrote:

On 9/22/23 12:28 PM, Kees Cook wrote:

quoted

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 checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct ipa_power.

Looks good, thanks.

Reviewed-by: Alex Elder <redacted>

Note that there is some interaction between struct ipa_power_data
and struct ipa_power (the former is used to initialize the latter).
Both of these contain flexible arrays counted by another field in
the structure.  It seems possible that the way these are initialized
might need slight modification to allow the compiler to do its
enforcement; if that's the case, please reach out to me.

I think it's all okay:

struct ipa_power_data {
        u32 core_clock_rate;
        u32 interconnect_count;         /* # entries in interconnect_data[] */
        const struct ipa_interconnect_data *interconnect_data;
};

"interconnect_data" here is a pointer, not a flexible array. (Yes,
__counted_by is expected to be expanded in the future for pointers,
but not yet.) Looking at initializers, I didn't see any problems with
how struct ipa_power is allocated.

Thanks for the heads-up; I'm sure I'll look at this again when we can
further expand __counted_by to pointers. :)

-Kees

-- 
Kees Cook