Cross-merge networking fixes after downstream PR (net-7.0-rc3).
No conflicts.
Adjacent changes:
net/netfilter/nft_set_rbtree.c
fb7fb40163 ("netfilter: nf_tables: clone set on flush only")
3aea466a43 ("netfilter: nft_set_rbtree: don't disable bh when acquiring tree lock")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
A socket using sockmap has its own independent receive queue: ingress_msg.
This queue may contain data from its own protocol stack or from other
sockets.
Therefore, for sockmap, relying solely on copied_seq and rcv_nxt to
calculate FIONREAD is not enough.
This patch adds a new msg_tot_len field in the psock structure to record
the data length in ingress_msg. Additionally, we implement new ioctl
interfaces for TCP and UDP to intercept FIONREAD operations.
Note that we intentionally do not include sk_receive_queue data in the
FIONREAD result. Data in sk_receive_queue has not yet been processed by
the BPF verdict program, and may be redirected to other sockets or
dropped. Including it would create semantic ambiguity since this data
may never be readable by the user.
Unix and VSOCK sockets have similar issues, but fixing them is outside
the scope of this patch as it would require more intrusive changes.
Previous work by John Fastabend made some efforts towards FIONREAD support:
commit e5c6de5fa0 ("bpf, sockmap: Incorrectly handling copied_seq")
Although the current patch is based on the previous work by John Fastabend,
it is acceptable for our Fixes tag to point to the same commit.
FD1:read()
-- FD1->copied_seq++
| [read data]
|
[enqueue data] v
[sockmap] -> ingress to self -> ingress_msg queue
FD1 native stack ------> ^
-- FD1->rcv_nxt++ -> redirect to other | [enqueue data]
| |
| ingress to FD1
v ^
... | [sockmap]
FD2 native stack
Fixes: 04919bed94 ("tcp: Introduce tcp_read_skb()")
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20260124113314.113584-3-jiayuan.chen@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
A socket using sockmap has its own independent receive queue: ingress_msg.
This queue may contain data from its own protocol stack or from other
sockets.
The issue is that when reading from ingress_msg, we update tp->copied_seq
by default. However, if the data is not from its own protocol stack,
tcp->rcv_nxt is not increased. Later, if we convert this socket to a
native socket, reading from this socket may fail because copied_seq might
be significantly larger than rcv_nxt.
This fix also addresses the syzkaller-reported bug referenced in the
Closes tag.
This patch marks the skmsg objects in ingress_msg. When reading, we update
copied_seq only if the data is from its own protocol stack.
FD1:read()
-- FD1->copied_seq++
| [read data]
|
[enqueue data] v
[sockmap] -> ingress to self -> ingress_msg queue
FD1 native stack ------> ^
-- FD1->rcv_nxt++ -> redirect to other | [enqueue data]
| |
| ingress to FD1
v ^
... | [sockmap]
FD2 native stack
Closes: https://syzkaller.appspot.com/bug?extid=06dbd397158ec0ea4983
Fixes: 04919bed94 ("tcp: Introduce tcp_read_skb()")
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://lore.kernel.org/r/20260124113314.113584-2-jiayuan.chen@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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: 4f738adba3 ("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
'sk->copied_seq' was updated in the tcp_eat_skb() function when the action
of a BPF program was SK_REDIRECT. For other actions, like SK_PASS, the
update logic for 'sk->copied_seq' was moved to tcp_bpf_recvmsg_parser()
to ensure the accuracy of the 'fionread' feature.
It works for a single stream_verdict scenario, as it also modified
sk_data_ready->sk_psock_verdict_data_ready->tcp_read_skb
to remove updating 'sk->copied_seq'.
However, for programs where both stream_parser and stream_verdict are
active (strparser purpose), tcp_read_sock() was used instead of
tcp_read_skb() (sk_data_ready->strp_data_ready->tcp_read_sock).
tcp_read_sock() now still updates 'sk->copied_seq', leading to duplicate
updates.
In summary, for strparser + SK_PASS, copied_seq is redundantly calculated
in both tcp_read_sock() and tcp_bpf_recvmsg_parser().
The issue causes incorrect copied_seq calculations, which prevent
correct data reads from the recv() interface in user-land.
We do not want to add new proto_ops to implement a new version of
tcp_read_sock, as this would introduce code complexity [1].
We could have added noack and copied_seq to desc, and then called
ops->read_sock. However, unfortunately, other modules didn’t fully
initialize desc to zero. So, for now, we are directly calling
tcp_read_sock_noack() in tcp_bpf.c.
[1]: https://lore.kernel.org/bpf/20241218053408.437295-1-mrpre@163.com
Fixes: e5c6de5fa0 ("bpf, sockmap: Incorrectly handling copied_seq")
Suggested-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Jiayuan Chen <mrpre@163.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://patch.msgid.link/20250122100917.49845-3-mrpre@163.com
bpf kselftest sockhash::test_txmsg_cork_hangs in test_sockmap.c triggers a
kernel NULL pointer dereference:
BUG: kernel NULL pointer dereference, address: 0000000000000008
? __die_body+0x6e/0xb0
? __die+0x8b/0xa0
? page_fault_oops+0x358/0x3c0
? local_clock+0x19/0x30
? lock_release+0x11b/0x440
? kernelmode_fixup_or_oops+0x54/0x60
? __bad_area_nosemaphore+0x4f/0x210
? mmap_read_unlock+0x13/0x30
? bad_area_nosemaphore+0x16/0x20
? do_user_addr_fault+0x6fd/0x740
? prb_read_valid+0x1d/0x30
? exc_page_fault+0x55/0xd0
? asm_exc_page_fault+0x2b/0x30
? splice_to_socket+0x52e/0x630
? shmem_file_splice_read+0x2b1/0x310
direct_splice_actor+0x47/0x70
splice_direct_to_actor+0x133/0x300
? do_splice_direct+0x90/0x90
do_splice_direct+0x64/0x90
? __ia32_sys_tee+0x30/0x30
do_sendfile+0x214/0x300
__se_sys_sendfile64+0x8e/0xb0
__x64_sys_sendfile64+0x25/0x30
x64_sys_call+0xb82/0x2840
do_syscall_64+0x75/0x110
entry_SYSCALL_64_after_hwframe+0x4b/0x53
This is caused by tcp_bpf_sendmsg() returning a larger value(12289) than
size (8192), which causes the while loop in splice_to_socket() to release
an uninitialized pipe buf.
The underlying cause is that this code assumes sk_msg_memcopy_from_iter()
will copy all bytes upon success but it actually might only copy part of
it.
This commit changes it to use the real copied bytes.
Signed-off-by: Levi Zim <rsworktech@outlook.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241130-tcp-bpf-sendmsg-v1-2-bae583d014f3@outlook.com
When we do sk_psock_verdict_apply->sk_psock_skb_ingress, an sk_msg will
be created out of the skb, and the rmem accounting of the sk_msg will be
handled by the skb.
For skmsgs in __SK_REDIRECT case of tcp_bpf_send_verdict, when redirecting
to the ingress of a socket, although we sk_rmem_schedule and add sk_msg to
the ingress_msg of sk_redir, we do not update sk_rmem_alloc. As a result,
except for the global memory limit, the rmem of sk_redir is nearly
unlimited. Thus, add sk_rmem_alloc related logic to limit the recv buffer.
Since the function sk_msg_recvmsg and __sk_psock_purge_ingress_msg are
used in these two paths. We use "msg->skb" to test whether the sk_msg is
skb backed up. If it's not, we shall do the memory accounting explicitly.
Fixes: 604326b41a ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241210012039.1669389-3-zijianzhang@bytedance.com
The current sk memory accounting logic in __SK_REDIRECT is pre-uncharging
tosend bytes, which is either msg->sg.size or a smaller value apply_bytes.
Potential problems with this strategy are as follows:
- If the actual sent bytes are smaller than tosend, we need to charge some
bytes back, as in line 487, which is okay but seems not clean.
- When tosend is set to apply_bytes, as in line 417, and (ret < 0), we may
miss uncharging (msg->sg.size - apply_bytes) bytes.
[...]
415 tosend = msg->sg.size;
416 if (psock->apply_bytes && psock->apply_bytes < tosend)
417 tosend = psock->apply_bytes;
[...]
443 sk_msg_return(sk, msg, tosend);
444 release_sock(sk);
446 origsize = msg->sg.size;
447 ret = tcp_bpf_sendmsg_redir(sk_redir, redir_ingress,
448 msg, tosend, flags);
449 sent = origsize - msg->sg.size;
[...]
454 lock_sock(sk);
455 if (unlikely(ret < 0)) {
456 int free = sk_msg_free_nocharge(sk, msg);
458 if (!cork)
459 *copied -= free;
460 }
[...]
487 if (eval == __SK_REDIRECT)
488 sk_mem_charge(sk, tosend - sent);
[...]
When running the selftest test_txmsg_redir_wait_sndmem with txmsg_apply,
the following warning will be reported:
------------[ cut here ]------------
WARNING: CPU: 6 PID: 57 at net/ipv4/af_inet.c:156 inet_sock_destruct+0x190/0x1a0
Modules linked in:
CPU: 6 UID: 0 PID: 57 Comm: kworker/6:0 Not tainted 6.12.0-rc1.bm.1-amd64+ #43
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Workqueue: events sk_psock_destroy
RIP: 0010:inet_sock_destruct+0x190/0x1a0
RSP: 0018:ffffad0a8021fe08 EFLAGS: 00010206
RAX: 0000000000000011 RBX: ffff9aab4475b900 RCX: ffff9aab481a0800
RDX: 0000000000000303 RSI: 0000000000000011 RDI: ffff9aab4475b900
RBP: ffff9aab4475b990 R08: 0000000000000000 R09: ffff9aab40050ec0
R10: 0000000000000000 R11: ffff9aae6fdb1d01 R12: ffff9aab49c60400
R13: ffff9aab49c60598 R14: ffff9aab49c60598 R15: dead000000000100
FS: 0000000000000000(0000) GS:ffff9aae6fd80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffec7e47bd8 CR3: 00000001a1a1c004 CR4: 0000000000770ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
? __warn+0x89/0x130
? inet_sock_destruct+0x190/0x1a0
? report_bug+0xfc/0x1e0
? handle_bug+0x5c/0xa0
? exc_invalid_op+0x17/0x70
? asm_exc_invalid_op+0x1a/0x20
? inet_sock_destruct+0x190/0x1a0
__sk_destruct+0x25/0x220
sk_psock_destroy+0x2b2/0x310
process_scheduled_works+0xa3/0x3e0
worker_thread+0x117/0x240
? __pfx_worker_thread+0x10/0x10
kthread+0xcf/0x100
? __pfx_kthread+0x10/0x10
ret_from_fork+0x31/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
---[ end trace 0000000000000000 ]---
In __SK_REDIRECT, a more concise way is delaying the uncharging after sent
bytes are finalized, and uncharge this value. When (ret < 0), we shall
invoke sk_msg_free.
Same thing happens in case __SK_DROP, when tosend is set to apply_bytes,
we may miss uncharging (msg->sg.size - apply_bytes) bytes. The same
warning will be reported in selftest.
[...]
468 case __SK_DROP:
469 default:
470 sk_msg_free_partial(sk, msg, tosend);
471 sk_msg_apply_bytes(psock, tosend);
472 *copied -= (tosend + delta);
473 return -EACCES;
[...]
So instead of sk_msg_free_partial we can do sk_msg_free here.
Fixes: 604326b41a ("bpf, sockmap: convert to generic sk_msg interface")
Fixes: 8ec95b9471 ("bpf, sockmap: Fix the sk->sk_forward_alloc warning of sk_stream_kill_queues")
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241016234838.3167769-3-zijianzhang@bytedance.com
The tcp_bpf_recvmsg_parser() function, running in user context,
retrieves seq_copied from tcp_sk without holding the socket lock, and
stores it in a local variable seq. However, the softirq context can
modify tcp_sk->seq_copied concurrently, for example, n tcp_read_sock().
As a result, the seq value is stale when it is assigned back to
tcp_sk->copied_seq at the end of tcp_bpf_recvmsg_parser(), leading to
incorrect behavior.
Due to concurrency, the copied_seq field in tcp_bpf_recvmsg_parser()
might be set to an incorrect value (less than the actual copied_seq) at
the end of function: 'WRITE_ONCE(tcp->copied_seq, seq)'. This causes the
'offset' to be negative in tcp_read_sock()->tcp_recv_skb() when
processing new incoming packets (sk->copied_seq - skb->seq becomes less
than 0), and all subsequent packets will be dropped.
Signed-off-by: Jiayuan Chen <mrpre@163.com>
Link: https://lore.kernel.org/r/20241028065226.35568-1-mrpre@163.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Daniel Borkmann says:
====================
pull-request: bpf-next 2024-09-11
We've added 12 non-merge commits during the last 16 day(s) which contain
a total of 20 files changed, 228 insertions(+), 30 deletions(-).
There's a minor merge conflict in drivers/net/netkit.c:
00d066a4d4 ("netdev_features: convert NETIF_F_LLTX to dev->lltx")
d966087948 ("netkit: Disable netpoll support")
The main changes are:
1) Enable bpf_dynptr_from_skb for tp_btf such that this can be used
to easily parse skbs in BPF programs attached to tracepoints,
from Philo Lu.
2) Add a cond_resched() point in BPF's sock_hash_free() as there have
been several syzbot soft lockup reports recently, from Eric Dumazet.
3) Fix xsk_buff_can_alloc() to account for queue_empty_descs which
got noticed when zero copy ice driver started to use it,
from Maciej Fijalkowski.
4) Move the xdp:xdp_cpumap_kthread tracepoint before cpumap pushes skbs
up via netif_receive_skb_list() to better measure latencies,
from Daniel Xu.
5) Follow-up to disable netpoll support from netkit, from Daniel Borkmann.
6) Improve xsk selftests to not assume a fixed MAX_SKB_FRAGS of 17 but
instead gather the actual value via /proc/sys/net/core/max_skb_frags,
also from Maciej Fijalkowski.
* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next:
sock_map: Add a cond_resched() in sock_hash_free()
selftests/bpf: Expand skb dynptr selftests for tp_btf
bpf: Allow bpf_dynptr_from_skb() for tp_btf
tcp: Use skb__nullable in trace_tcp_send_reset
selftests/bpf: Add test for __nullable suffix in tp_btf
bpf: Support __nullable argument suffix for tp_btf
bpf, cpumap: Move xdp:xdp_cpumap_kthread tracepoint before rcv
selftests/xsk: Read current MAX_SKB_FRAGS from sysctl knob
xsk: Bump xsk_queue::queue_empty_descs in xp_can_alloc()
tcp_bpf: Remove an unused parameter for bpf_tcp_ingress()
bpf, sockmap: Correct spelling skmsg.c
netkit: Disable netpoll support
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
====================
Link: https://patch.msgid.link/20240911211525.13834-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As reported by Tom, .NET and applications build on top of it rely
on connect(AF_UNSPEC) to async cancel pending I/O operations on TCP
socket.
The blamed commit below caused a regression, as such cancellation
can now fail.
As suggested by Eric, this change addresses the problem explicitly
causing blocking I/O operation to terminate immediately (with an error)
when a concurrent disconnect() is executed.
Instead of tracking the number of threads blocked on a given socket,
track the number of disconnect() issued on such socket. If such counter
changes after a blocking operation releasing and re-acquiring the socket
lock, error out the current operation.
Fixes: 4faeee0cf8 ("tcp: deny tcp_disconnect() when threads are waiting")
Reported-by: Tom Deseyn <tdeseyn@redhat.com>
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1886305
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/f3b95e47e3dbed840960548aebaa8d954372db41.1697008693.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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: e5c6de5fa0 ("bpf, sockmap: Incorrectly handling copied_seq")
Fixes: 04919bed94 ("tcp: Introduce tcp_read_skb()")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20230926035300.135096-3-john.fastabend@gmail.com
The read_skb() logic is incrementing the tcp->copied_seq which is used for
among other things calculating how many outstanding bytes can be read by
the application. This results in application errors, if the application
does an ioctl(FIONREAD) we return zero because this is calculated from
the copied_seq value.
To fix this we move tcp->copied_seq accounting into the recv handler so
that we update these when the recvmsg() hook is called and data is in
fact copied into user buffers. This gives an accurate FIONREAD value
as expected and improves ACK handling. Before we were calling the
tcp_rcv_space_adjust() which would update 'number of bytes copied to
user in last RTT' which is wrong for programs returning SK_PASS. The
bytes are only copied to the user when recvmsg is handled.
Doing the fix for recvmsg is straightforward, but fixing redirect and
SK_DROP pkts is a bit tricker. Build a tcp_psock_eat() helper and then
call this from skmsg handlers. This fixes another issue where a broken
socket with a BPF program doing a resubmit could hang the receiver. This
happened because although read_skb() consumed the skb through sock_drop()
it did not update the copied_seq. Now if a single reccv socket is
redirecting to many sockets (for example for lb) the receiver sk will be
hung even though we might expect it to continue. The hang comes from
not updating the copied_seq numbers and memory pressure resulting from
that.
We have a slight layer problem of calling tcp_eat_skb even if its not
a TCP socket. To fix we could refactor and create per type receiver
handlers. I decided this is more work than we want in the fix and we
already have some small tweaks depending on caller that use the
helper skb_bpf_strparser(). So we extend that a bit and always set
the strparser bit when it is in use and then we can gate the
seq_copied updates on this.
Fixes: 04919bed94 ("tcp: Introduce tcp_read_skb()")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20230523025618.113937-9-john.fastabend@gmail.com
