Re: [PATCH net-next 2/2] ath10k: fix ath10k_pci struct layout

[Kalle Valo]

Arnd Bergmann <arnd@xxxxxxxx> writes:

> gcc-10 correctly points out a bug with a zero-length array in
> struct ath10k_pci:
>
> drivers/net/wireless/ath/ath10k/ahb.c: In function 'ath10k_ahb_remove':
> drivers/net/wireless/ath/ath10k/ahb.c:30:9: error: array subscript 0
> is outside the bounds of an interior zero-length array 'struct
> ath10k_ahb[0]' [-Werror=zero-length-bounds]
>    30 |  return &((struct ath10k_pci *)ar->drv_priv)->ahb[0];
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from drivers/net/wireless/ath/ath10k/ahb.c:13:
> drivers/net/wireless/ath/ath10k/pci.h:185:20: note: while referencing 'ahb'
>   185 |  struct ath10k_ahb ahb[0];
>       |                    ^~~
>
> The last addition to the struct ignored the comments and added
> new members behind the array that must remain last.
>
> Change it to a flexible-array member and move it last again to
> make it work correctly, prevent the same thing from happening
> again (all compilers warn about flexible-array members in the
> middle of a struct) and get it to build without warnings.

Very good find, thanks! This bug would cause all sort of strange memory
corruption issues.

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches