wifi: carl9170: re-fix fortified-memset warning

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: wifi: carl9170: re-fix fortified-memset warning The carl9170_tx_release() function sometimes triggers a fortified-memset warning in my randconfig builds: In file included from include/linux/string.h:254, from drivers/net/wireless/ath/carl9170/tx.c:40: In function 'fortify_memset_chk', inlined from 'carl9170_tx_release' at drivers/net/wireless/ath/carl9170/tx.c:283:2, inlined from 'kref_put' at include/linux/kref.h:65:3, inlined from 'carl9170_tx_put_skb' at drivers/net/wireless/ath/carl9170/tx.c:342:9: include/linux/fortify-string.h:493:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] 493 | __write_overflow_field(p_size_field, size); Kees previously tried to avoid this by using memset_after(), but it seems this does not fully address the problem. I noticed that the memset_after() here is done on a different part of the union (status) than the original cast was from (rate_driver_data), which may confuse the compiler. Unfortunately, the memset_after() trick does not work on driver_rates[] because that is part of an anonymous struct, and I could not get struct_group() to do this either. Using two separate memset() calls on the two members does address the warning though.

References

• https://git.kernel.org/stable/c/13857683126e8a6492af73c74d702835f7a2175b
• https://git.kernel.org/stable/c/87586467098281f04fa93e59fe3a516b954bddc4
• https://git.kernel.org/stable/c/0c38c9c460bb8ce8d6f6cf316e0d71a70983ec83
• https://git.kernel.org/stable/c/042a39bb8e0812466327a5102606e88a5a4f8c02
• https://git.kernel.org/stable/c/066afafc10c9476ee36c47c9062527a17e763901