This is a note to let you know that I've just added the patch titled
bpf, sockmap: Do not inc copied_seq when PEEK flag set
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-sockmap-do-not-inc-copied_seq-when-peek-flag-set.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4c7577da359b1848b7ebe21ad1273bcbb999b140
Author: John Fastabend <john.fastabend@xxxxxxxxx>
Date: Mon Sep 25 20:52:59 2023 -0700
bpf, sockmap: Do not inc copied_seq when PEEK flag set
[ Upstream commit da9e915eaf5dadb1963b7738cdfa42ed55212445 ]
When data is peek'd off the receive queue we shouldn't considered it
copied from tcp_sock side. When we increment copied_seq this will confuse
tcp_data_ready() because copied_seq can be arbitrarily increased. From
application side it results in poll() operations not waking up when
expected.
Notice tcp stack without BPF recvmsg programs also does not increment
copied_seq.
We broke this when we moved copied_seq into recvmsg to only update when
actual copy was happening. But, it wasn't working correctly either before
because the tcp_data_ready() tried to use the copied_seq value to see
if data was read by user yet. See fixes tags.
Fixes: e5c6de5fa0258 ("bpf, sockmap: Incorrectly handling copied_seq")
Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()")
Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Reviewed-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20230926035300.135096-3-john.fastabend@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 81f0dff69e0b6..3272682030015 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -222,6 +222,7 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk,
int *addr_len)
{
struct tcp_sock *tcp = tcp_sk(sk);
+ int peek = flags & MSG_PEEK;
u32 seq = tcp->copied_seq;
struct sk_psock *psock;
int copied = 0;
@@ -311,7 +312,8 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk,
copied = -EAGAIN;
}
out:
- WRITE_ONCE(tcp->copied_seq, seq);
+ if (!peek)
+ WRITE_ONCE(tcp->copied_seq, seq);
tcp_rcv_space_adjust(sk);
if (copied > 0)
__tcp_cleanup_rbuf(sk, copied);
