CVE-2024-41005

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

netpoll: Fix race condition in netpoll_owner_active

KCSAN detected a race condition in netpoll:

BUG: KCSAN: data-race in net_rx_action / netpoll_send_skb
write (marked) to 0xffff8881164168b0 of 4 bytes by interrupt on cpu 10:
net_rx_action (./include/linux/netpoll.h:90 net/core/dev.c:6712 net/core/dev.c:6822)

<snip> read to 0xffff8881164168b0 of 4 bytes by task 1 on cpu 2: netpoll_send_skb (net/core/netpoll.c:319 net/core/netpoll.c:345 net/core/netpoll.c:393) netpoll_send_udp (net/core/netpoll.c:?) <snip> value changed: 0x0000000a -> 0xffffffff

This happens because netpoll_owner_active() needs to check if the current CPU is the owner of the lock, touching napi->poll_owner non atomically. The ->poll_owner field contains the current CPU holding the lock.

Use an atomic read to check if the poll owner is the current CPU.