CVE-2025-39913

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

tcpbpf: Call skmsgfree() when tcpbpfsendverdict() fails to allocate psock->cork.

syzbot reported the splat below. [0]

The repro does the following:

1. Load a skmsg prog that calls bpfmsgcorkbytes(msg, cork_bytes)
2. Attach the prog to a SOCKMAP
3. Add a socket to the SOCKMAP
4. Activate fault injection
5. Send data less than cork_bytes

At 5., the data is carried over to the next sendmsg() as it is smaller than the corkbytes specified by bpfmsgcorkbytes().

Then, tcpbpfsend_verdict() tries to allocate psock->cork to hold the data, but this fails silently due to fault injection + _GFPNOWARN.

If the allocation fails, we need to revert the sk->skforwardalloc change done by skmsgalloc().

Let's call skmsgfree() when tcpbpfsend_verdict fails to allocate psock->cork.

The "*copied" also needs to be updated such that a proper error can be returned to the caller, sendmsg. It fails to allocate psock->cork. Nothing has been corked so far, so this patch simply sets "*copied" to 0.

Modules linked in: CPU: 1 UID: 0 PID: 5983 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:inetsockdestruct+0x623/0x730 net/ipv4/af_inet.c:156 Code: 0f 0b 90 e9 62 fe ff ff e8 7a db b5 f7 90 0f 0b 90 e9 95 fe ff ff e8 6c db b5 f7 90 0f 0b 90 e9 bb fe ff ff e8 5e db b5 f7 90 <0f> 0b 90 e9 e1 fe ff ff 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c 9f fc RSP: 0018:ffffc90000a08b48 EFLAGS: 00010246 RAX: ffffffff8a09d0b2 RBX: dffffc0000000000 RCX: ffff888024a23c80 RDX: 0000000000000100 RSI: 0000000000000fff RDI: 0000000000000000 RBP: 0000000000000fff R08: ffff88807e07c627 R09: 1ffff1100fc0f8c4 R10: dffffc0000000000 R11: ffffed100fc0f8c5 R12: ffff88807e07c380 R13: dffffc0000000000 R14: ffff88807e07c60c R15: 1ffff1100fc0f872 FS: 00005555604c4500(0000) GS:ffff888125af1000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005555604df5c8 CR3: 0000000032b06000 CR4: 00000000003526f0 Call Trace: <IRQ> __skdestruct+0x86/0x660 net/core/sock.c:2339 rcudobatch kernel/rcu/tree.c:2605 [inline] rcucore+0xca8/0x1770 kernel/rcu/tree.c:2861 handle_softirqs+0x286/0x870 kernel/softirq.c:579 __dosoftirq kernel/softirq.c:613 [inline] invokesoftirq kernel/softirq.c:453 [inline] _irqexitrcu+0xca/0x1f0 kernel/softirq.c:680 irqexitrcu+0x9/0x30 kernel/softirq.c:696 instrsysvecapictimerinterrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvecapictimerinterrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052 </IRQ>