5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@google.com
[ Upstream commit a3967baad4d533dc254c31e0d221e51c8d223d58 ]
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>
Fixes: 4f738adba30a ("bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data") Reported-by: syzbot+4cabd1d2fa917a456db8@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/68c0b6b5.050a0220.3c6139.0013.GAE@google.com/ Signed-off-by: Kuniyuki Iwashima kuniyu@google.com Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Link: https://patch.msgid.link/20250909232623.4151337-1-kuniyu@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/tcp_bpf.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 8c1508a2e241a..df0b9edd4e87e 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -336,8 +336,11 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock, if (!psock->cork) { psock->cork = kzalloc(sizeof(*psock->cork), GFP_ATOMIC | __GFP_NOWARN); - if (!psock->cork) + if (!psock->cork) { + sk_msg_free(sk, msg); + *copied = 0; return -ENOMEM; + } } memcpy(psock->cork, msg, sizeof(*msg)); return 0;