CVE-2026-53223

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

net: guard timestamp cmsgs to real error queue skbs

skb_is_err_queue() treats PACKET_OUTGOING as the sole marker for an skb

from sk_error_queue. That assumption is not true for AF_PACKET sockets:

outgoing packet taps are also delivered to packet sockets with

skb->pkt_type == PACKET_OUTGOING, but their skb->cb is owned by AF_PACKET

instead of struct sock_exterr_skb.

If such an skb is received with timestamping enabled, the generic

timestamp cmsg path can read AF_PACKET control-buffer state as

sock_exterr_skb::opt_stats. With SO_RXQ_OVFL enabled, the packet drop

counter overlaps opt_stats. An odd drop count makes the path emit

SCM_TIMESTAMPING_OPT_STATS with skb->len and skb->data. For non-linear

skbs this copies past the linear head and can trigger hardened usercopy or

disclose adjacent heap contents.

Keep skb_is_err_queue() local to net/socket.c, but make it verify that

the PACKET_OUTGOING marker is paired with the sock_rmem_free destructor

installed by sock_queue_err_skb(). AF_PACKET receive skbs use normal

receive ownership and no longer pass as error-queue skbs, while legitimate

sk_error_queue entries keep the PACKET_OUTGOING marker and sock_rmem_free

ownership.