In the Linux kernel, the following vulnerability has been resolved:
net: drop_monitor: fix info leak in NET_DM_ATTR_PAYLOAD
net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() open code
the NET_DM_ATTR_PAYLOAD attribute to avoid zeroing the packet payload
before overwriting it with skb_copy_bits().
skb_put() reserves nla_total_size(payload_len), i.e. the header plus the
NLA_ALIGN() padding, but only payload_len bytes are copied in. When
payload_len is not a multiple of 4 the 1-3 padding bytes are never
initialized and are leaked to user space inside the netlink message.
KMSAN confirms the leak for the software path when the packet payload
length is not 4-byte aligned:
BUG: KMSAN: kernel-infoleak in _copy_to_iter
_copy_to_iter
__skb_datagram_iter
skb_copy_datagram_iter
netlink_recvmsg
sock_recvmsg
__sys_recvfrom
Uninit was created at:
kmem_cache_alloc_node_noprof
__alloc_skb
net_dm_packet_work
Bytes 173-175 of 176 are uninitialized
Use __nla_reserve(), which sets up the attribute header and zeroes the
padding, instead of open coding the attribute construction.