CVE-2025-39913

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

tcp_bpf: Call sk_msg_free() when tcp_bpf_send_verdict() fails to allocate psock->cork.

syzbot reported the splat below. [0]

The repro does the following:

1. Load a sk_msg prog that calls bpf_msg_cork_bytes(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 cork_bytes specified by bpf_msg_cork_bytes().

Then, tcp_bpf_send_verdict() tries to allocate psock->cork to hold

the data, but this fails silently due to fault injection + __GFP_NOWARN.

If the allocation fails, we need to revert the sk->sk_forward_alloc

change done by sk_msg_alloc().

Let's call sk_msg_free() when tcp_bpf_send_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.

[0]:

WARNING: net/ipv4/af_inet.c:156 at inet_sock_destruct+0x623/0x730 net/ipv4/af_inet.c:156, CPU#1: syz-executor/5983

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:inet_sock_destruct+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>

__sk_destruct+0x86/0x660 net/core/sock.c:2339

rcu_do_batch kernel/rcu/tree.c:2605 [inline]

rcu_core+0xca8/0x1770 kernel/rcu/tree.c:2861

handle_softirqs+0x286/0x870 kernel/softirq.c:579

__do_softirq kernel/softirq.c:613 [inline]

invoke_softirq kernel/softirq.c:453 [inline]

__irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680

irq_exit_rcu+0x9/0x30 kernel/softirq.c:696

instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]

sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052

</IRQ>