From: Jiayuan Chen <jiayuan.chen@linux.dev>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
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
Subject: Re: [PATCH bpf v2 10/15] bpf, sockmap: Reset the copy position when corking
Date: Tue, 3 Nov 2026 09:39:04 +0800 [thread overview]
Message-ID: <c5a1ce12-2c0c-489b-840b-1cef8cda999c@linux.dev> (raw)
In-Reply-To: <20261102072112.4160195-11-alexei.starovoitov@gmail.com>
On 11/2/26 3:21 PM, Alexei Starovoitov wrote:
> From: Chris Mason <mason@kernel.org>
>
> sk_msg_memcopy_from_iter() writes to the copy position: byte sg.copybreak
> after the offset of element sg.curr. Both tcp_bpf_push() and sk_msg_xfer()
> remove bytes from the front of an element. They increase its offset, but
> they do not change sg.copybreak when the element is sg.curr.
>
> tcp_bpf_send_verdict() can send a part of a message and keep the rest as
> the cork. tcp_bpf_sendmsg() appends new data to it. If sk_msg_alloc() then
> extends element sg.curr, the peer can get memory that nobody wrote:
>
> old offset offset end of data offset + sg.copybreak
> | removed | rest | not written | new data
>
> Move sk_msg_reset_curr() from filter.c to skmsg.h. Call it when a message
> becomes the cork, as the helpers that change a message do. It sets the copy
> position to the end of the data. Without removed bytes it changes nothing.
>
> Fixes: 91843d540a13 ("bpf: sockmap, add msg_cork_bytes() helper")
> Signed-off-by: Chris Mason <mason@kernel.org>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
next prev parent reply other threads:[~2026-11-03 1:39 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 7:20 [PATCH bpf v2 00/15] bpf, sockmap: Fixes for verdicts, redirects, corks and recvmsg() Alexei Starovoitov
2026-11-02 7:20 ` [PATCH bpf v2 01/15] bpf, sockmap: Write sg.start when recvmsg() faults Alexei Starovoitov
2026-11-02 8:32 ` Jiayuan Chen
2026-11-02 7:20 ` [PATCH bpf v2 02/15] bpf, sockmap: Don't let an SK_DROP verdict stick Alexei Starovoitov
2026-11-02 8:45 ` Jiayuan Chen
2026-11-02 18:47 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 03/15] bpf, sockmap: Don't let an SK_PASS verdict cover the next message Alexei Starovoitov
2026-11-02 18:51 ` John Fastabend
2026-11-02 22:44 ` Alexei Starovoitov
2026-11-02 7:21 ` [PATCH bpf v2 04/15] bpf, sockmap: Subtract all dropped bytes from the return value Alexei Starovoitov
2026-11-02 11:19 ` Jiayuan Chen
2026-11-02 19:12 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 05/15] bpf, sockmap: Clear the resume state of a stopped psock Alexei Starovoitov
2026-11-02 11:40 ` Jiayuan Chen
2026-11-02 19:16 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 06/15] bpf, sockmap: Give no progs to a TCP listener Alexei Starovoitov
2026-11-02 12:00 ` Jiayuan Chen
2026-11-02 19:31 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 07/15] bpf, sockmap: Check the target of an egress redirect before each send Alexei Starovoitov
2026-11-02 12:32 ` Jiayuan Chen
2026-11-02 16:18 ` Alexei Starovoitov
2026-11-02 19:36 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 08/15] net: Leave sk_stream_wait_memory() once the socket is dead Alexei Starovoitov
2026-11-02 12:54 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 09/15] bpf, sockmap: Check the TCP state in recvmsg() Alexei Starovoitov
2026-11-02 15:15 ` Jiayuan Chen
2026-11-02 16:57 ` Matthieu Baerts
2026-11-02 7:21 ` [PATCH bpf v2 10/15] bpf, sockmap: Reset the copy position when corking Alexei Starovoitov
2026-11-03 1:39 ` Jiayuan Chen [this message]
2026-11-02 7:21 ` [PATCH bpf v2 11/15] bpf, sockmap: Don't copy 0 bytes into a full cork Alexei Starovoitov
2026-11-03 1:41 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 12/15] bpf, sockmap: Clear the redirect target before the sk_msg prog runs Alexei Starovoitov
2026-11-03 1:58 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 13/15] bpf, sockmap: Check that the redirected message is the cork Alexei Starovoitov
2026-11-03 2:07 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 14/15] bpf, sockmap: Keep the rest of the cork after a redirect Alexei Starovoitov
2026-11-03 2:25 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 15/15] bpf, sockmap: Clear the end mark of elements added by push and pop Alexei Starovoitov
2026-11-03 2:51 ` Jiayuan Chen
2026-11-02 20:11 ` [PATCH bpf v2 00/15] bpf, sockmap: Fixes for verdicts, redirects, corks and recvmsg() John Fastabend
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