In the Linux kernel, the following vulnerability has been resolved:
mptcp: deal with large GSO size
After the blamed commit below, the TCP sockets (and the MPTCP subflows) can build egress packets larger than 64K. That exceeds the maximum DSS data size, the length being misrepresent on the wire and the stream being corrupted, as later observed on the receiver:
WARNING: CPU: 0 PID: 9696 at net/mptcp/protocol.c:705 _mptcpmoveskbsfromsubflow+0x2604/0x26e0
CPU: 0 PID: 9696 Comm: syz-executor.7 Not tainted 6.6.0-rc5-gcd8bdf563d46 #45
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
netlink: 8 bytes leftover after parsing attributes in process syz-executor.4'.
RIP: 0010:__mptcp_move_skbs_from_subflow+0x2604/0x26e0 net/mptcp/protocol.c:705
RSP: 0018:ffffc90000006e80 EFLAGS: 00010246
RAX: ffffffff83e9f674 RBX: ffff88802f45d870 RCX: ffff888102ad0000
netlink: 8 bytes leftover after parsing attributes in process
syz-executor.4'.
RDX: 0000000080000303 RSI: 0000000000013908 RDI: 0000000000003908
RBP: ffffc90000007110 R08: ffffffff83e9e078 R09: 1ffff1100e548c8a
R10: dffffc0000000000 R11: ffffed100e548c8b R12: 0000000000013908
R13: dffffc0000000000 R14: 0000000000003908 R15: 000000000031cf29
FS: 00007f239c47e700(0000) GS:ffff88811b200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f239c45cd78 CR3: 000000006a66c006 CR4: 0000000000770ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
PKRU: 55555554
Call Trace:
<IRQ>
mptcpdataready+0x263/0xac0 net/mptcp/protocol.c:819
subflowdataready+0x268/0x6d0 net/mptcp/subflow.c:1409
tcpdataqueue+0x21a1/0x7a60 net/ipv4/tcpinput.c:5151
tcprcvestablished+0x950/0x1d90 net/ipv4/tcpinput.c:6098
tcpv6dorcv+0x554/0x12f0 net/ipv6/tcpipv6.c:1483
tcpv6rcv+0x2e26/0x3810 net/ipv6/tcpipv6.c:1749
ip6protocoldeliverrcu+0xd6b/0x1ae0 net/ipv6/ip6input.c:438
ip6input+0x1c5/0x470 net/ipv6/ip6input.c:483
ipv6rcv+0xef/0x2c0 include/linux/netfilter.h:304
_netifreceiveskb+0x1ea/0x6a0 net/core/dev.c:5532
processbacklog+0x353/0x660 net/core/dev.c:5974
_napipoll+0xc6/0x5a0 net/core/dev.c:6536
netrxaction+0x6a0/0xfd0 net/core/dev.c:6603
_dosoftirq+0x184/0x524 kernel/softirq.c:553
dosoftirq+0xdd/0x130 kernel/softirq.c:454
Address the issue explicitly bounding the maximum GSO size to what MPTCP actually allows.