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Koichiro Den 8314944cc3 net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs 
[ Upstream commit 7f083faf59 ]

When shrinking the number of real tx queues,
netif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush
qdiscs for queues which will no longer be used.

qdisc_reset_all_tx_gt() currently serializes qdisc_reset() with
qdisc_lock(). However, for lockless qdiscs, the dequeue path is
serialized by qdisc_run_begin/end() using qdisc->seqlock instead, so
qdisc_reset() can run concurrently with __qdisc_run() and free skbs
while they are still being dequeued, leading to UAF.

This can easily be reproduced on e.g. virtio-net by imposing heavy
traffic while frequently changing the number of queue pairs:

  iperf3 -ub0 -c $peer -t 0 &
  while :; do
    ethtool -L eth0 combined 1
    ethtool -L eth0 combined 2
  done

With KASAN enabled, this leads to reports like:

  BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760
  ...
  Call Trace:
   <TASK>
   ...
   __qdisc_run+0x133f/0x1760
   __dev_queue_xmit+0x248f/0x3550
   ip_finish_output2+0xa42/0x2110
   ip_output+0x1a7/0x410
   ip_send_skb+0x2e6/0x480
   udp_send_skb+0xb0a/0x1590
   udp_sendmsg+0x13c9/0x1fc0
   ...
   </TASK>

  Allocated by task 1270 on cpu 5 at 44.558414s:
   ...
   alloc_skb_with_frags+0x84/0x7c0
   sock_alloc_send_pskb+0x69a/0x830
   __ip_append_data+0x1b86/0x48c0
   ip_make_skb+0x1e8/0x2b0
   udp_sendmsg+0x13a6/0x1fc0
   ...

  Freed by task 1306 on cpu 3 at 44.558445s:
   ...
   kmem_cache_free+0x117/0x5e0
   pfifo_fast_reset+0x14d/0x580
   qdisc_reset+0x9e/0x5f0
   netif_set_real_num_tx_queues+0x303/0x840
   virtnet_set_channels+0x1bf/0x260 [virtio_net]
   ethnl_set_channels+0x684/0xae0
   ethnl_default_set_doit+0x31a/0x890
   ...

Serialize qdisc_reset_all_tx_gt() against the lockless dequeue path by
taking qdisc->seqlock for TCQ_F_NOLOCK qdiscs, matching the
serialization model already used by dev_reset_queue().

Additionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state
reflects an empty queue, avoiding needless re-scheduling.

Fixes: 6b3ba9146f ("net: sched: allow qdiscs to handle locking")
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Link: https://patch.msgid.link/20260228145307.3955532-1-den@valinux.co.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-12 07:09:57 -04:00
arch ARM: clean up the memset64() C wrapper 2026-03-12 07:09:44 -04:00
block block: decouple secure erase size limit from discard size limit 2026-03-04 07:19:38 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation hwmon: (aht10) Add support for dht20 2026-03-12 07:09:46 -04:00
drivers hwmon: (max6639) fix inverted polarity 2026-03-12 07:09:57 -04:00
fs smb/client: fix buffer size for smb311_posix_qinfo in SMB311_posix_query_info() 2026-03-12 07:09:56 -04:00
include net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs 2026-03-12 07:09:57 -04:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: fix user_ref race between scrub and refill paths 2026-03-04 07:21:33 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel timekeeping: Fix timex status validation for auxiliary clocks 2026-03-12 07:09:57 -04:00
lib debugobject: Make it work with deferred page initialization - again 2026-03-12 07:09:08 -04:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm: thp: deny THP for files on anonymous inodes 2026-03-12 07:09:41 -04:00
net net: ipv4: fix ARM64 alignment fault in multipath hash seed 2026-03-12 07:09:56 -04:00
rust rust: kunit: fix warning when !CONFIG_PRINTK 2026-03-12 07:09:52 -04:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts kbuild: rpm-pkg: Disable automatic requires for manual debuginfo package 2026-03-04 07:21:32 -05:00
security ima: verify the previous kernel's IMA buffer lies in addressable RAM 2026-03-04 07:21:17 -05:00
sound ASoC: fsl_xcvr: provide regmap names 2026-03-12 07:09:44 -04:00
tools kunit: tool: copy caller args in run_kernel to prevent mutation 2026-03-12 07:09:52 -04:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.16 2026-03-04 07:25:12 -05:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.