From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E6DD3218DE for ; Wed, 10 Sep 2025 14:05:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757513160; cv=none; b=uz7y9jeu2CBS/haBOPJJo/EOJDphLbqEXvKOD/iN1itd5E6lNSuLg+PNhJSNuHNdFRFvA0JQ5dk2HaB2DdnRxqIgaKqlCBqaB3ehgCFARiAvwNeqqOMLCZdeNQrQoGaRP7B1o7QQc0BxSXjeSURwxsis6FYPCShfPYnoB9vZAAg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757513160; c=relaxed/simple; bh=Bjhex7LejrbRQaESQF5Epo/8YEFXGCfX/zfXr9uPhYE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EkXdbtWHHhY76NB5LdsCAtav+yESJ2RhTnbZM7x9zH+icUXE3a6G/MT2S/EB4de8BJ18/m/sReuJ3hWyHpkOKCN5rplQxbcDxIozlhga8WF2JE++1Fw3HaFGhzpq7a08Wlk+dU/9O2aOSvi/eybbGRvhDHv3pMuYWzbxvJ404gQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=n7PmtqlO; arc=none smtp.client-ip=95.215.58.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="n7PmtqlO" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1757513156; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/7/m/rIMOan/KvaJDI/7faZKA7j5+5vMGRzv9YnAqCQ=; b=n7PmtqlOoANH8MFq4N43pNmgqxju3jBfwrmJRdS2rw6Bcz/+rp2HPeZcPDNjjoeigbq2OS WifDv0/lAyQIZwMT4NFOEjIWACyr40nHgLl3J7bY5o7ybti+ocUfOOkRQjmr9DdtWLdhOj Pq3vGnefsF1duEzaKTAkb6SWP68nj10= Date: Wed, 10 Sep 2025 07:05:46 -0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v1 bpf] tcp_bpf: Call sk_msg_free() when tcp_bpf_send_verdict() fails to allocate psock->cork. To: Kuniyuki Iwashima Cc: John Fastabend , Jakub Sitnicki , Alexei Starovoitov , Daniel Borkmann , Kuniyuki Iwashima , netdev@vger.kernel.org, bpf@vger.kernel.org, syzbot+4cabd1d2fa917a456db8@syzkaller.appspotmail.com References: <20250909232623.4151337-1-kuniyu@google.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 9/9/25 11:56 PM, Kuniyuki Iwashima wrote: > On Tue, Sep 9, 2025 at 10:15 PM Martin KaFai Lau wrote: >> >> On 9/9/25 4:26 PM, Kuniyuki Iwashima wrote: >>> 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. >>> >>> [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: >>> >>> __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 >>> >>> >>> 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 >>> --- >>> net/ipv4/tcp_bpf.c | 4 +++- >>> 1 file changed, 3 insertions(+), 1 deletion(-) >>> >>> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c >>> index ba581785adb4..ee6a371e65a4 100644 >>> --- a/net/ipv4/tcp_bpf.c >>> +++ b/net/ipv4/tcp_bpf.c >>> @@ -408,8 +408,10 @@ 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); >> >> Nothing has been corked yet, does it need to update the "*copied": >> >> *copied -= sk_msg_free(sk, msg); > > Oh exactly, or simply *copied = 0 ? Make sense. I made the change and updated the commit message for this fix also. Applied. Thanks.