In the Linux kernel, the following vulnerability has been resolved:
packet: use consistent hard_header_len in non-ring send paths
packet_snd() reads dev->hard_header_len multiple times while allocating
and constructing an skb. Device reconfiguration can change this value
concurrently, for example through bonding device type changes. For SOCK_RAW, packet_snd() can save a larger value in reserve and later
allocate headroom using a smaller value.
Moving skb->data back by reserve
then places it before skb->head, and the following copy from userspace can
attempt an out-of-bounds write.
packet_sendmsg_spkt() has the same issue because it calculates its
reservation and header offset from separate reads before dropping the RCU
read lock to allocate the skb. Add LL_RESERVED_SPACE_EX() for callers that already saved a header length. Read hard_header_len once in packet_snd() and use it for allocation and
construction.
In packet_sendmsg_spkt(), preserve the allocation-time value
through the device lookup retry. The separate SOCK_DGRAM consistency problem between hard_header_len and
header_ops->create is not addressed here.
Attack Parameters
Impact Assessment
CVSS Vector v3.1