From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.241 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793670124; b=Xl5q3EfnM1J32X6+yKsIHyj5M/Dzmi8fBNE+bhX50VZZ+blCXnF+RPqcOc3fyfy2TFO8 LIFd736Sp+aLMSx1SDskBjKIkigDKm/Q2TxDGh9tZ9z/RcJARVI4c7MS3N6ONT+8FmV2K eSHeJUlhoAdN3ss3TLJ5N5gKClwvdBpmvQcVX82JqTHszbKwF6RIuzhJ30WRvbxxkOuwk UmjPIY4it9BoZvQPjecph/AJedRUXBDEIVJ4tfQgTQ6ONsueV3nGPVS1WUh5118QTeWYv No6ejSimxFCrR1D7ys9dBbMWvZ1X63JqM6sdO565bEnBG0bgwdYLDZJUn7U/h0WOLsA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793670124; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding; bh=dGnaZBUj0XNcB11772fHKRR4jnMCSTKoOZ96EtQkLP8=; b=kiKVOtIsOPqznaXYZsA0AV9GFtwMlhfhIVQwWBZfkUptsD409bJvEo8DcNguBBwGd76J U7R1JKTbDtwBtUa6IlYAsk+KiPPW4+Ja/fKn9tTqIIJGW/w4wT9tcRa4cLYpFjFYG1Xtb cfErG1L5fqKsHE0xUvQduVYtYvpxcDnUZ8bbOfmV1pPJoz+1IArhbBTt31hjPZWNBz5FH j/wrH2p+QYigf+YOW6iK+rOGvkzo89wVD4CkqdLR7QolXgEWF2k5KlinpprWNsv93IBus lkSfYAu8oAOGz4BYpDgBGC1BKhhJBTPNHS7WdX0K0kTmGwViRj89FPtRYOAk3V2r1Wg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=fKH70yEb; arc=none smtp.remote-ip=95.215.58.241 Received: from mta1.migadu.com (out-241.mta1.migadu.com [95.215.58.241]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5FA2C606A327 for ; Tue, 3 Nov 2026 01:42:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 5FA2C606A327 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, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=fKH70yEb X-Envelope-To: mptcp@lists.linux.dev DKIM-Signature: a=rsa-sha256; bh=dGnaZBUj0XNcB11772fHKRR4jnMCSTKoOZ96EtQkLP8=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793670121; v=1; x=1794274921; b=fKH70yEbYDywQGAwgfKSS+FjmYqpdNjx/QAS6L7HT/xmTPtjFKacyw2MbKh0akpklTS9OHgd koVAORicRuRu3tQLsfJU9vw1xGIoAAdyPRjlLZcrpLoB9v3kYqa4Gj0jnTKUox/RvMJ0oLPNMh6 k8yttt+zw5PAe78xF3bDXib8= X-Envelope-To: mptcp@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id 4aed7de82dbe24fe; Tue, 03 Nov 2026 01:42:01 +0000 X-Mizu-Trace-ID: 4aed7de82dbe24fe X-Migadu-Flow: FLOW_OUT Message-ID: Date: Tue, 3 Nov 2026 09:41:52 +0800 X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf v2 11/15] bpf, sockmap: Don't copy 0 bytes into a full cork To: Alexei Starovoitov , bpf@vger.kernel.org, netdev@vger.kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, john.fastabend@gmail.com, jakub@cloudflare.com, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, kuniyu@google.com, willemb@google.com, matttbe@kernel.org, mptcp@lists.linux.dev, mason@kernel.org, josef@toxicpanda.com References: <20261102072112.4160195-1-alexei.starovoitov@gmail.com> <20261102072112.4160195-12-alexei.starovoitov@gmail.com> From: Jiayuan Chen In-Reply-To: <20261102072112.4160195-12-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/2/26 3:21 PM, Alexei Starovoitov wrote: > From: Chris Mason > > psock->cork is a ring. sk_msg_memcopy_from_iter() writes at sg.curr. > sk_msg_alloc() adds room at sg.end, where a full ring has a spare element. > > When only a part of the data fits, tcp_bpf_sendmsg() copies this part and > flushes the cork. If nothing fits, it copies 0 bytes. This copy writes > nothing, but it moves sg.curr to sg.end and returns -ENOSPC. Thus sendmsg() > fails without a flush. sg.curr stays at sg.end, and from there a copy moves > it past the spare element. Then a copy can skip the first new element, and > the peer gets memory that nobody wrote. > > Skip the copy when sk_msg_alloc() adds nothing, as tls_sw_sendmsg_locked() > does. This pass of the loop flushes the cork. The flush empties the element > at sg.curr, thus the copy in the next pass starts at the first new element. > Now sendmsg() on a full cork does not fail with ENOSPC. The prog runs on > less data than it wants to cork, as it does when a part fits. > > The first Fixes tag is for the -ENOSPC without a flush. The commit in the > second tag added the spare element. Since then sg.curr can move past it. > > Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") > Fixes: 031097d9e079 ("net: skmsg: fix TLS 1.3 crash with full sk_msg") > Signed-off-by: Chris Mason > Signed-off-by: Alexei Starovoitov Reviewed-by: Jiayuan Chen