CVE-2024-46676: Divide By Zero

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

nfc: pn533: Add poll mod list filling check

In case of im_protocols value is 1 and tm_protocols value is 0 this combination successfully passes the check 'if (!im_protocols && !tm_protocols)' in the nfc_start_poll(). But then after pn533_poll_create_mod_list() call in pn533_start_poll() poll mod list will remain empty and dev->poll_mod_count will remain 0 which lead to division by zero.

Normally no im protocol has value 1 in the mask, so this combination is not expected by driver. But these protocol values actually come from userspace via Netlink interface (NFC_CMD_START_POLL operation). So a broken or malicious program may pass a message containing a "bad" combination of protocol parameter values so that dev->poll_mod_count is not incremented inside pn533_poll_create_mod_list(), thus leading to division by zero. Call trace looks like: nfc_genl_start_poll() nfc_start_poll() ->start_poll() pn533_start_poll()

Add poll mod list filling check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.