kernel/linux.git/drivers/net/wireguard/queueing.h, branch v6.19.11

wireguard: queueing: always return valid online CPU in wg_cpumask_choose_online()

2025-09-12T01:52:21+00:00

The function gets number of online CPUS, and uses it to search for Nth cpu in cpu_online_mask. If id == num_online_cpus() - 1, and one CPU gets offlined between calling num_online_cpus() -> cpumask_nth(), there's a chance for cpumask_nth() to find nothing and return >= nr_cpu_ids. The caller code in __queue_work() tries to avoid that by checking the returned CPU against WORK_CPU_UNBOUND, which is NR_CPUS. It's not the same as '>= nr_cpu_ids'. On a typical Ubuntu desktop, NR_CPUS is 8192, while nr_cpu_ids is the actual number of possible CPUs, say 8. The non-existing cpu may later be passed to rcu_dereference() and corrupt the logic. Fix it by switching from 'if' to 'while'. Suggested-by: Jason A. Donenfeld Signed-off-by: Yury Norov (NVIDIA) Signed-off-by: Jason A. Donenfeld Link: https://patch.msgid.link/20250910013644.4153708-3-Jason@zx2c4.com Signed-off-by: Jakub Kicinski

wireguard: queueing: simplify wg_cpumask_next_online()

2025-09-12T01:52:20+00:00

wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the function significantly simpler. While there, fix opencoded cpu_online() too. Signed-off-by: Yury Norov Reviewed-by: Simon Horman Signed-off-by: Jason A. Donenfeld Link: https://patch.msgid.link/20250910013644.4153708-2-Jason@zx2c4.com Signed-off-by: Jakub Kicinski

wireguard: queueing: annotate intentional data race in cpu round robin

2024-07-06T00:21:10+00:00

KCSAN reports a race in the CPU round robin function, which, as the comment points out, is intentional: BUG: KCSAN: data-race in wg_packet_send_staged_packets / wg_packet_send_staged_packets read to 0xffff88811254eb28 of 4 bytes by task 3160 on cpu 1: wg_cpumask_next_online drivers/net/wireguard/queueing.h:127 [inline] wg_queue_enqueue_per_device_and_peer drivers/net/wireguard/queueing.h:173 [inline] wg_packet_create_data drivers/net/wireguard/send.c:320 [inline] wg_packet_send_staged_packets+0x60e/0xac0 drivers/net/wireguard/send.c:388 wg_packet_send_keepalive+0xe2/0x100 drivers/net/wireguard/send.c:239 wg_receive_handshake_packet drivers/net/wireguard/receive.c:186 [inline] wg_packet_handshake_receive_worker+0x449/0x5f0 drivers/net/wireguard/receive.c:213 process_one_work kernel/workqueue.c:3248 [inline] process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3329 worker_thread+0x526/0x720 kernel/workqueue.c:3409 kthread+0x1d1/0x210 kernel/kthread.c:389 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 write to 0xffff88811254eb28 of 4 bytes by task 3158 on cpu 0: wg_cpumask_next_online drivers/net/wireguard/queueing.h:130 [inline] wg_queue_enqueue_per_device_and_peer drivers/net/wireguard/queueing.h:173 [inline] wg_packet_create_data drivers/net/wireguard/send.c:320 [inline] wg_packet_send_staged_packets+0x6e5/0xac0 drivers/net/wireguard/send.c:388 wg_packet_send_keepalive+0xe2/0x100 drivers/net/wireguard/send.c:239 wg_receive_handshake_packet drivers/net/wireguard/receive.c:186 [inline] wg_packet_handshake_receive_worker+0x449/0x5f0 drivers/net/wireguard/receive.c:213 process_one_work kernel/workqueue.c:3248 [inline] process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3329 worker_thread+0x526/0x720 kernel/workqueue.c:3409 kthread+0x1d1/0x210 kernel/kthread.c:389 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 value changed: 0xffffffff -> 0x00000000 Mark this race as intentional by using READ/WRITE_ONCE(). Cc: stable@vger.kernel.org Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Link: https://patch.msgid.link/20240704154517.1572127-4-Jason@zx2c4.com Signed-off-by: Jakub Kicinski

wireguard: queueing: use saner cpu selection wrapping

2023-07-03T08:17:52+00:00

Using `% nr_cpumask_bits` is slow and complicated, and not totally robust toward dynamic changes to CPU topologies. Rather than storing the next CPU in the round-robin, just store the last one, and also return that value. This simplifies the loop drastically into a much more common pattern. Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Cc: stable@vger.kernel.org Reported-by: Linus Torvalds Tested-by: Manuel Leiner Signed-off-by: Jason A. Donenfeld Signed-off-by: David S. Miller

cpumask: fix incorrect cpumask scanning result checks

2023-03-06T20:15:13+00:00

It turns out that commit 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask optimizations") exposed a number of cases of drivers not checking the result of "cpumask_next()" and friends correctly. The documented correct check for "no more cpus in the cpumask" is to check for the result being equal or larger than the number of possible CPU ids, exactly _because_ we've always done those constant-sized cpumask scans using a widened type before. So the return value of a cpumask scan should be checked with if (cpu >= nr_cpu_ids) ... because the cpumask scan did not necessarily stop exactly *at* that maximum CPU id. But a few cases ended up instead using checks like if (cpu == nr_cpumask_bits) ... which used that internal "widened" number of bits. And that used to work pretty much by accident (ok, in this case "by accident" is simply because it matched the historical internal implementation of the cpumask scanning, so it was more of a "intentionally using implementation details rather than an accident"). But the extended constant-sized optimizations then did that internal implementation differently, and now that code that did things wrong but matched the old implementation no longer worked at all. Which then causes subsequent odd problems due to using what ends up being an invalid CPU ID. Most of these cases require either unusual hardware or special uses to hit, but the random.c one triggers quite easily. All you really need is to have a sufficiently small CONFIG_NR_CPUS value for the bit scanning optimization to be triggered, but not enough CPUs to then actually fill that widened cpumask. At that point, the cpumask scanning will return the NR_CPUS constant, which is _not_ the same as nr_cpumask_bits. This just does the mindless fix with sed -i 's/== nr_cpumask_bits/>= nr_cpu_ids/' to fix the incorrect uses. The ones in the SCSI lpfc driver in particular could probably be fixed more cleanly by just removing that repeated pattern entirely, but I am not emptionally invested enough in that driver to care. Reported-and-tested-by: Guenter Roeck Link: https://lore.kernel.org/lkml/481b19b5-83a0-4793-b4fd-194ad7b978c3@roeck-us.net/ Reported-and-tested-by: Geert Uytterhoeven Link: https://lore.kernel.org/lkml/CAMuHMdUKo_Sf7TjKzcNDa8Ve+6QrK+P8nSQrSQ=6LTRmcBKNww@mail.gmail.com/ Reported-by: Vernon Yang Link: https://lore.kernel.org/lkml/20230306160651.2016767-1-vernon2gm@gmail.com/ Cc: Yury Norov Cc: Jason A. Donenfeld Signed-off-by: Linus Torvalds

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2021-12-02T19:44:56+00:00

Signed-off-by: Jakub Kicinski

wireguard: receive: use ring buffer for incoming handshakes

2021-11-30T03:50:50+00:00

Apparently the spinlock on incoming_handshake's skb_queue is highly contended, and a torrent of handshake or cookie packets can bring the data plane to its knees, simply by virtue of enqueueing the handshake packets to be processed asynchronously. So, we try switching this to a ring buffer to hopefully have less lock contention. This alleviates the problem somewhat, though it still isn't perfect, so future patches will have to improve this further. However, it at least doesn't completely diminish the data plane. Reported-by: Streun Fabio Reported-by: Joel Wanner Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Signed-off-by: Jakub Kicinski

skbuff: Switch structure bounds to struct_group()

2021-11-22T15:13:54+00:00

In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memcpy(), memmove(), and memset(), avoid intentionally writing across neighboring fields. Replace the existing empty member position markers "headers_start" and "headers_end" with a struct_group(). This will allow memcpy() and sizeof() to more easily reason about sizes, and improve readability. "pahole" shows no size nor member offset changes to struct sk_buff. "objdump -d" shows no object code changes (outside of WARNs affected by source line number changes). Signed-off-by: Kees Cook Reviewed-by: Gustavo A. R. Silva Reviewed-by: Jason A. Donenfeld # drivers/net/wireguard/* Link: https://lore.kernel.org/lkml/20210728035006.GD35706@embeddedor Signed-off-by: David S. Miller

wireguard: queueing: get rid of per-peer ring buffers

2021-02-23T23:59:34+00:00

Having two ring buffers per-peer means that every peer results in two massive ring allocations. On an 8-core x86_64 machine, this commit reduces the per-peer allocation from 18,688 bytes to 1,856 bytes, which is an 90% reduction. Ninety percent! With some single-machine deployments approaching 500,000 peers, we're talking about a reduction from 7 gigs of memory down to 700 megs of memory. In order to get rid of these per-peer allocations, this commit switches to using a list-based queueing approach. Currently GSO fragments are chained together using the skb->next pointer (the skb_list_* singly linked list approach), so we form the per-peer queue around the unused skb->prev pointer (which sort of makes sense because the links are pointing backwards). Use of skb_queue_* is not possible here, because that is based on doubly linked lists and spinlocks. Multiple cores can write into the queue at any given time, because its writes occur in the start_xmit path or in the udp_recv path. But reads happen in a single workqueue item per-peer, amounting to a multi-producer, single-consumer paradigm. The MPSC queue is implemented locklessly and never blocks. However, it is not linearizable (though it is serializable), with a very tight and unlikely race on writes, which, when hit (some tiny fraction of the 0.15% of partial adds on a fully loaded 16-core x86_64 system), causes the queue reader to terminate early. However, because every packet sent queues up the same workqueue item after it is fully added, the worker resumes again, and stopping early isn't actually a problem, since at that point the packet wouldn't have yet been added to the encryption queue. These properties allow us to avoid disabling interrupts or spinning. The design is based on Dmitry Vyukov's algorithm [1]. Performance-wise, ordinarily list-based queues aren't preferable to ringbuffers, because of cache misses when following pointers around. However, we *already* have to follow the adjacent pointers when working through fragments, so there shouldn't actually be any change there. A potential downside is that dequeueing is a bit more complicated, but the ptr_ring structure used prior had a spinlock when dequeueing, so all and all the difference appears to be a wash. Actually, from profiling, the biggest performance hit, by far, of this commit winds up being atomic_add_unless(count, 1, max) and atomic_ dec(count), which account for the majority of CPU time, according to perf. In that sense, the previous ring buffer was superior in that it could check if it was full by head==tail, which the list-based approach cannot do. But all and all, this enables us to get massive memory savings, allowing WireGuard to scale for real world deployments, without taking much of a performance hit. [1] http://www.1024cores.net/home/lock-free-algorithms/queues/intrusive-mpsc-node-based-queue Reviewed-by: Dmitry Vyukov Reviewed-by: Toke Høiland-Jørgensen Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Signed-off-by: Jakub Kicinski

wireguard: queueing: make use of ip_tunnel_parse_protocol

2020-06-30T19:29:39+00:00

Now that wg_examine_packet_protocol has been added for general consumption as ip_tunnel_parse_protocol, it's possible to remove wg_examine_packet_protocol and simply use the new ip_tunnel_parse_protocol function directly. Signed-off-by: Jason A. Donenfeld Signed-off-by: David S. Miller