Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

wifi: mac80211: handle empty FILS association request payload

fils_encrypt_assoc_req() accepts a (Re)Association Request frame whose last element is the FILS Session element. crypt_len is then zero and aes_siv_encrypt() is called with an empty plaintext.

kmemdup() returns ZERO_SIZE_PTR for a zero-length allocation, so the unconditional sg_init_one() puts an invalid page into the scatterlist. With CONFIG_DEBUG_SG this triggers a kernel BUG in sg_set_buf(); without the debug check the bogus page is handed to the crypto backend.

AES-SIV is defined for empty plaintext and the S2V result is then the complete output, so handle this case before the CTR step, which has nothing to encrypt.