CVE-2026-53223

Description

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.

References

• https://git.kernel.org/stable/c/1ee90b77b727df903033db873c75caac5c27ec98
• https://git.kernel.org/stable/c/24a0d548d3a765cd4558224e4f8e06e14cba26e3
• https://git.kernel.org/stable/c/3dde4fb941fa5649ab809f6cd3e20e0c424a4e31
• https://git.kernel.org/stable/c/71ff5cdd5da61d0438e902aa0fd68c28bc901abe
• https://git.kernel.org/stable/c/ad9a0374ee6d11048e1f74cd5180bad58b9848b4