CVE-2024-26853: In the Linux kernel, the following vulnerability has been resolved:  igc: avoid returning frame twice in XDP_REDIRECT  When a frame can not be transmitted in XDP_REDIRECT (e.g. due to a full queue), it is necessary to free it by calling xdp_return_frame_rx_napi.  However, this is the responsibility of the caller of the ndo_xdp_xmit (see for example bq_xmit_all in kernel/bpf/devmap.c) and thus calling it inside igc_xdp_xmit (which is the ndo_xdp_xmit of the igc driver) as well will lead to memory corruption.  In fact, bq_xmit_all expects that it can return all frames after the last successfully transmitted one. Therefore, break for the first not transmitted frame, but do not call xdp_return_frame_rx_napi in igc_xdp_xmit. This is equally implemented in other Intel drivers such as the igb.  There are two alternatives to this that were rejected: 1. Return num_frames as all the frames would have been    transmitted and release them inside igc_xdp_xmit.    While it might work technically, it is not what    the return value is meant to represent (i.e. the    number of SUCCESSFULLY transmitted packets). 2. Rework kernel/bpf/devmap.c and all drivers to    support non-consecutively dropped packets.    Besides being complex, it likely has a negative    performance impact without a significant gain    since it is anyway unlikely that the next frame    can be transmitted if the previous one was dropped.  The memory corruption can be reproduced with the following script which leads to a kernel panic after a few seconds.  It basically generates more traffic than a i225 NIC can transmit and pushes it via XDP_REDIRECT from a virtual interface to the physical interface where frames get dropped.     #!/bin/bash    INTERFACE=enp4s0    INTERFACE_IDX=`cat /sys/class/net/$INTERFACE/ifindex`     sudo ip link add dev veth1 type veth peer name veth2    sudo ip link set up $INTERFACE    sudo ip link set up veth1    sudo ip link set up veth2     cat << EOF > redirect.bpf.c     SEC("prog")    int redirect(struct xdp_md *ctx)    {        return bpf_redirect($INTERFACE_IDX, 0);    }     char _license[] SEC("license") = "GPL";    EOF    clang -O2 -g -Wall -target bpf -c redirect.bpf.c -o redirect.bpf.o    sudo ip link set veth2 xdp obj redirect.bpf.o     cat << EOF > pass.bpf.c     SEC("prog")    int pass(struct xdp_md *ctx)    {        return XDP_PASS;    }     char _license[] SEC("license") = "GPL";    EOF    clang -O2 -g -Wall -target bpf -c pass.bpf.c -o pass.bpf.o    sudo ip link set $INTERFACE xdp obj pass.bpf.o     cat << EOF > trafgen.cfg     {      /* Ethernet Header */      0xe8, 0x6a, 0x64, 0x41, 0xbf, 0x46,      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,      const16(ETH_P_IP),       /* IPv4 Header */      0b01000101, 0,   # IPv4 version, IHL, TOS      const16(1028),   # IPv4 total length (UDP length + 20 bytes (IP header))      const16(2),      # IPv4 ident      0b01000000, 0,   # IPv4 flags, fragmentation off      64,              # IPv4 TTL      17,              # Protocol UDP      csumip(14, 33),  # IPv4 checksum       /* UDP Header */      10,  0, 1, 1,    # IP Src - adapt as needed      10,  0, 1, 2,    # IP Dest - adapt as needed      const16(6666),   # UDP Src Port      const16(6666),   # UDP Dest Port      const16(1008),   # UDP length (UDP header 8 bytes + payload length)      csumudp(14, 34), # UDP checksum       /* Payload */      fill('W', 1000),    }    EOF     sudo trafgen -i trafgen.cfg -b3000MB -o veth1 --cpp