wifi: mac80211: handle empty FILS association request payload

Overview

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.

Affected

• Linux >= 39404feee691a2dc524a629ed6eb5cfe5d8898d1 < 2f5b62f6534d336a62fdb9e88b186dd70b4323ef
• Linux >= 39404feee691a2dc524a629ed6eb5cfe5d8898d1 < 452f1c9b76f7a122bbc4630b9691bda4809677c4
• Linux >= 39404feee691a2dc524a629ed6eb5cfe5d8898d1 < 20f939b0c151d1d28e6b62a76b2454fa6fe877f2
• Linux >= 39404feee691a2dc524a629ed6eb5cfe5d8898d1 < 5bfd4b0b40b79781d900cb2f7da0685070f53c67
• Linux 4.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.