linux.git/net/core/dev.c, branch v7.3-rc3

net: cap tx_queue_len at S16_MAX to prevent oversized ring allocations

2026-09-04T23:30:48+00:00

Several subsystems allocate ring buffers sized by dev->tx_queue_len
with no upper bound. An unprivileged user (via unshare -Urn) can set a
huge tx_queue_len and exhaust global memory with ring allocations:

- pfifo_fast: pfifo_fast_init() and pfifo_fast_change_tx_queue_len()
  allocate 3 skb_array rings of tx_queue_len entries each.
- tun: tun_queue_resize() and the queue-attach path resize ptr_rings
  to tx_queue_len on the NETDEV_CHANGE_TX_QUEUE_LEN notifier.
- tap (macvtap/ipvtap): tap_queue_resize() and tap_init() resize/init
  ptr_rings to tx_queue_len on the same notifier.

netif_change_tx_queue_len() is the single entry point for IFLA_TXQLEN,
sysfs, and the SIOCSIFTXQLEN ioctl. Cap new_len at S16_MAX (32767)
there so the oversized value is rejected at set time. This takes
effect whether the device is up or down, before dev->tx_queue_len is
written, before any notifier fires, and before any ring is allocated.
The "> S16_MAX" check also subsumes the previous unsigned-long
truncation test, and a negative ifr_qlen from the ioctl lands far
above the cap after conversion, so both old failure modes are covered
by the one comparison.

tx_queue_len is ambigious: both a per-ring sizing multiplier and a
default queue-length/limit knob for consumers that allocate
nothing at set time (pfifo/bfifo/gred/plug/sfb limits, htb
direct_qlen, qfq max_classes, teql). 32767 is chosen as the largest
value NLA_POLICY_FULL_RANGE can express for the u32 IFLA_TXQLEN
policy in patch 2/3 while staying a legitimate queue length on
high-BDP paths; the ring-memory trade-off of a shared knob is
disclosed below.

Conditions to recreate the bug:
- CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y.
- Unprivileged user in a fresh user+net namespace (unshare -Urn).
- pfifo_fast: create veth pairs, set tx_queue_len to 500000, attach
  mq+pfifo_fast. ~28 iterations OOMs a 2GB guest.
- tun: create 50 tun devices with IFF_MULTI_QUEUE, set tx_queue_len to
  500000, open 8 queues each. ~1.6GB of ptr_ring allocations OOMs a
  512MB guest.
- tap: same as tun with IFF_TAP. ~960MB OOMs a 512MB guest.
- On the fixed kernel the oversized tx_queue_len is rejected with
  -ERANGE at set time (all four paths: RTM_SETLINK, RTM_NEWLINK
  create, sysfs, ioctl - the latter two via this check, the former
  two via this check and the 2/3 parse policy respectively).

Fixes: 6a643ddb5624 ("net: introduce helper dev_change_tx_queue_len()")
Reported-by: Vega 
Closes: https://lore.kernel.org/netdev/20260828121902.66837-1-jhs@mojatatu.com/
Tested-by: Victor Nogueira 
Signed-off-by: Jamal Hadi Salim 
Link: https://patch.msgid.link/QDISC-2899.v2.20260901233641@mojatatu.com
Signed-off-by: Jakub Kicinski

net: Remove conflicting altnames for dying netns in __dev_change_net_namespace().

2026-09-03T01:30:00+00:00

syzbot reported the warning in cfg80211_pernet_exit(). [0]

The repro does the following:

  1. create two device in root netns and non-root netns
  2. assign the same altname for the two devices
  3. remove the non-root netns

Since commit 7663d522099e ("net: check for altname conflicts
when changing netdev's netns"), cfg80211_switch_netns() and
cfg802154_switch_netns() fail if init_net has a device with the
conflicting altname.

default_device_exit_net() had the same issue and commit d09486a04f5d
("net: fix removing a namespace with conflicting altnames") fixed it.

cfg80211_pernet_exit() and cfg802154_pernet_exit() need the same fix.

Let's generalise the fix by removing conflicting altnames for dying
netns in __dev_change_net_namespace().

[0]:
cfg80211_switch_netns(rdev, &init_net)
WARNING: net/wireless/core.c:1871 at cfg80211_pernet_exit+0xd5/0x120 net/wireless/core.c:1871, CPU#1: kworker/u8:9/1160
Modules linked in:
CPU: 1 UID: 0 PID: 1160 Comm: kworker/u8:9 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: netns cleanup_net
RIP: 0010:cfg80211_pernet_exit+0xd5/0x120 net/wireless/core.c:1871
Code: e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 b4 ef 0e f7 4d 8b 36 49 81 fe 20 10 4a 90 74 12 e8 03 3d 9f f6 eb 85 e8 fc 3c 9f f6 90 <0f> 0b 90 eb cc e8 f1 3c 9f f6 eb 05 e8 ea 3c 9f f6 5b 41 5c 41 5e
RSP: 0018:ffffc900057a78f0 EFLAGS: 00010293
RAX: ffffffff8b287154 RBX: ffff88807ba72780 RCX: ffff8880213e8000
RDX: 0000000000000000 RSI: 00000000ffffffef RDI: 0000000000000000
RBP: 00000000ffffffef R08: ffffffff9024cc67 R09: 0000000000000000
R10: fffff52000af4eb0 R11: fffffbfff204998d R12: dffffc0000000000
R13: ffffffff904a1080 R14: ffff888144ed0008 R15: ffff888144ed0e20
FS:  0000000000000000(0000) GS:ffff888124de6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005642de0a8a70 CR3: 000000007a40c000 CR4: 00000000003526f0
Call Trace:
 
 ops_exit_list net/core/net_namespace.c:200 [inline]
 ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:253
 cleanup_net+0x572/0x810 net/core/net_namespace.c:706
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 

Fixes: 36fbf1e52bd3 ("net: rtnetlink: add linkprop commands to add and delete alternative ifnames")
Reported-by: syzbot+74f338e09f1ef3ee6457@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6a96219e.04428c52.29b18.0001.GAE@google.com/T/
Signed-off-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20260901005550.2042357-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski

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

2026-08-18T17:42:41+00:00

Merge in late fixes in preparation for the net-next PR.

Conflicts:

drivers/dpll/dpll_core.c
drivers/dpll/dpll_netlink.c
  33f016b23a219 ("dpll: fix NULL deref in dpll_device_ops() during teardown race")
  b1d0c412088e3 ("dpll: add STATE_CONNECTED_OVERRIDE pin capability")
https://lore.kernel.org/aoR9YYY2P5--3x0N@sirena.org.uk
https://lore.kernel.org/aoR9VmKllVGwmQn_@sirena.org.uk

No adjacent changes.

Signed-off-by: Jakub Kicinski

net: add missing ref_tracker_dir_exit() to alloc_netdev_mqs()

2026-08-18T17:02:33+00:00

sashiko is reporting that trying to read /sys/kernel/debug/ref_tracker/*
causes use-afer-free crash when either alloc_percpu() or dev_addr_init()
in alloc_netdev_mqs() failed, for commit 4d92b95ff2f9 ("net: add net device
refcount tracker infrastructure") added ref_tracker_dir_exit() to only
free_netdev() path.

Closes: https://sashiko.dev/#/patchset/56c707e7-1fb0-43ec-b8fb-cf6f451e513e%40I-love.SAKURA.ne.jp
Fixes: 4d92b95ff2f9 ("net: add net device refcount tracker infrastructure")
Signed-off-by: Tetsuo Handa 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/b06ce35d-e7bc-47a5-8e0a-e82be7e4dd08@I-love.SAKURA.ne.jp
Signed-off-by: Jakub Kicinski

net: add READ_ONCE()/WRITE_ONCE() annotations for dev->prio_tc_map

2026-08-17T17:27:48+00:00

Concurrent fast-path readers access dev->prio_tc_map (e.g. via
skb_tx_hash(), netdev_get_prio_tc_map(), and qdiscs) while writers
update entries in dev->prio_tc_map or reset/clear the map via
netdev_reset_tc() and netdev_unbind_sb_channel().

Furthermore, memset() in netdev_reset_tc() and
netdev_unbind_sb_channel() provides no guarantee of performing
atomic word/byte stores.

Add READ_ONCE() and WRITE_ONCE() annotations to netdev_get_prio_tc_map()
and netdev_set_prio_tc_map(), replace memset() in dev.c with explicit
WRITE_ONCE() loops, and update direct array accesses in qdiscs to use
netdev_get_prio_tc_map().

Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20260812085440.3917924-4-edumazet@google.com
Signed-off-by: Jakub Kicinski

net: add READ_ONCE()/WRITE_ONCE() annotations for dev->num_tc

2026-08-17T17:27:48+00:00

Several fast-path and control-path lockless readers access dev->num_tc
(e.g., skb_tx_hash(), netdev_txq_to_tc(), netdev_get_num_tc(), and
qdisc/driver lookups) while concurrent writers update dev->num_tc
during TC setup, device reset, or channel configuration.

Add READ_ONCE() and WRITE_ONCE() annotations to prevent compiler
reordering and load/store tearing when accessing dev->num_tc.

Update inline helpers in netdevice.h (netdev_get_num_tc(),
netdev_set_prio_tc_map(), and netdev_get_sb_channel()) as well as
writers and lockless readers in core networking code and drivers.

Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20260812085440.3917924-3-edumazet@google.com
Signed-off-by: Jakub Kicinski

net: prevent torn reads in netdev_tc_txq

2026-08-17T17:27:48+00:00

netdev_set_tc_queue() (and related helpers/drivers such as
netdev_bind_sb_channel_queue(), netdev_reset_tc(), and
netdev_unbind_sb_channel()) perform separate 16-bit writes to
dev->tc_to_txq[tc].count and dev->tc_to_txq[tc].offset.

Furthermore, memset() in netdev_reset_tc() and
netdev_unbind_sb_channel() provides no guarantee of performing
full 32-bit word stores.

Concurrent lockless readers (e.g. skb_tx_hash(), netdev_txq_to_tc(),
ixgbe_select_queue(), taprio, mqprio, FPE drivers) can observe torn
values where offset and count belong to inconsistent configurations.

Redefine struct netdev_tc_txq to embed count and offset inside a union
with a u32 combined field, allowing atomic manipulation via
READ_ONCE() and WRITE_ONCE().

Update all lockless readers and writers across the kernel to use
READ_ONCE() and WRITE_ONCE() on the combined field.

Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20260812085440.3917924-2-edumazet@google.com
Signed-off-by: Jakub Kicinski

bpf, xdp: move offload check into dev_xdp_install()

2026-08-17T17:04:49+00:00

bpf_xdp_link_update() calls dev_xdp_install() directly and skips
dev_xdp_attach(), so the checks in dev_xdp_attach() do not run. A user can
make an XDP link with a normal program and then swap in an offloaded or
device-bound program with BPF_LINK_UPDATE, which puts it on the software
path.

dev_xdp_install() is the one place all three paths go through:
"ip link set xdp" and BPF_LINK_CREATE reach it via dev_xdp_attach(), and
BPF_LINK_UPDATE calls it directly. So move the program checks (offloaded,
bound to another device, device-bound in generic mode, native vs generic,
DEVMAP and CPUMAP) there, and keep only the netlink-flag check
(XDP_FLAGS_UPDATE_IF_NOEXIST) in dev_xdp_attach().

Fixes: 026a4c28e1db3 ("bpf, xdp: Implement LINK_UPDATE for BPF XDP link")
Signed-off-by: Jiayuan Chen 
Signed-off-by: Jakub Kicinski

Merge tag 'nf-next-26-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next

2026-08-14T19:23:12+00:00

Pablo Neira Ayuso says:

====================
Netfilter updates for net

This includes an enhancement to detect ct memleaks easier via
DEBUG_NET and flowtable preparation patches for IPv4 over IPV6
and vice-versa. This also includes a fix for the nft_ct custom
expectation support.

1) Add DEBUG_NET_WARN_ON_ONCE to nf_ct_set() to spot ct memleaks.

2) Pass struct net_device_path_ctx to dev_fill_forward_path() to
   make it easier to pass more parameters to this function.
   From Lorenzo Bianconi.

3) Add ether_type field to net_device_path context structucture.

4) Rename tun.l3_proto field to tun.inner_proto.

5) Rename ctx.tun.proto to ctx.tun.inner_proto.

6) Store ether_type in flowtable context.

7) Move IPv4 and IPv6 xmit path to a helper function.

8) Move encapsulation header parser out of the flowtable lookup
   function.

9) Rework nft_ct custom expectation support to address a possible
   reallocation of ct extension area while expectation list also
   contains expectations. Move datapath to a ct helper to fix it.

10) Ensure timeout is always lowered for the non-closing RST case
    in the TCP connection tracking.

11) Bail out when inserting already dead expectation, this should
    not ever happen, hence report it via DEBUG_NET.

12) Comestic updates for improving the conntrack selftest dump and
    flush userspace program, from Qingshuang Fu.

* tag 'nf-next-26-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next:
  selftests: netfilter: conntrack_dump_flush: remove unused variables and fix typo
  netfilter: nf_conntrack_expect: bail out on insert dead expectations
  netfilter: conntrack: always lower timeout for non-closing RST packets
  netfilter: nft_ct: move custom expectation support to helper
  netfilter: flowtable: detach layer 2 encapsulation parser from lookup
  netfilter: flowtable: move ipv4 and ipv6 xmit path to function
  netfilter: flowtable: store ethertype in flowtable context
  netfilter: flowtable: rename ctx.tun.proto to ctx.tun.inner_proto
  netfilter: flowtable: rename tun.l3_proto to tun.inner_proto
  net: netfilter: add ether_type to net_device_path_ctx and use it
  net: pass net_device_path_ctx to dev_fill_forward_path()
  netfilter: add DEBUG_NET_WARN_ON_ONCE to skb_set_nfct()
====================

Link: https://patch.msgid.link/20260810194015.932627-1-pablo@netfilter.org
Signed-off-by: Jakub Kicinski

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

2026-08-13T18:00:14+00:00

Cross-merge networking fixes after downstream PR (net-7.2-rc8).

No conflicts.

Adjacent changes:

drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
  5f3a13e0bb5e ("net: ngbe: fix NULL pointer dereference in non-MSI-X interrupt enabling")
  d661abdc30c2 ("net: ngbe: correct misleading interrupt comment")

drivers/net/ipvlan/ipvlan_main.c
  e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev")
  00a40d809207 ("ipvlan: Support per-netns netdev unregistration.")

Signed-off-by: Jakub Kicinski