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Tetsuo Handa a3c8fede03 xfrm: always flush state and policy upon NETDEV_UNREGISTER event 
[ Upstream commit 4efa91a285 ]

syzbot is reporting that "struct xfrm_state" refcount is leaking.

  unregister_netdevice: waiting for netdevsim0 to become free. Usage count = 2
  ref_tracker: netdev@ffff888052f24618 has 1/1 users at
       __netdev_tracker_alloc include/linux/netdevice.h:4400 [inline]
       netdev_tracker_alloc include/linux/netdevice.h:4412 [inline]
       xfrm_dev_state_add+0x3a5/0x1080 net/xfrm/xfrm_device.c:316
       xfrm_state_construct net/xfrm/xfrm_user.c:986 [inline]
       xfrm_add_sa+0x34ff/0x5fa0 net/xfrm/xfrm_user.c:1022
       xfrm_user_rcv_msg+0x58e/0xc00 net/xfrm/xfrm_user.c:3507
       netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2550
       xfrm_netlink_rcv+0x71/0x90 net/xfrm/xfrm_user.c:3529
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg net/socket.c:742 [inline]
       ____sys_sendmsg+0xa5d/0xc30 net/socket.c:2592
       ___sys_sendmsg+0x134/0x1d0 net/socket.c:2646
       __sys_sendmsg+0x16d/0x220 net/socket.c:2678
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

This is because commit d77e38e612 ("xfrm: Add an IPsec hardware
offloading API") implemented xfrm_dev_unregister() as no-op despite
xfrm_dev_state_add() from xfrm_state_construct() acquires a reference
to "struct net_device".
I guess that that commit expected that NETDEV_DOWN event is fired before
NETDEV_UNREGISTER event fires, and also assumed that xfrm_dev_state_add()
is called only if (dev->features & NETIF_F_HW_ESP) != 0.

Sabrina Dubroca identified steps to reproduce the same symptoms as below.

  echo 0 > /sys/bus/netdevsim/new_device
  dev=$(ls -1 /sys/bus/netdevsim/devices/netdevsim0/net/)
  ip xfrm state add src 192.168.13.1 dst 192.168.13.2 proto esp \
     spi 0x1000 mode tunnel aead 'rfc4106(gcm(aes))' $key 128   \
     offload crypto dev $dev dir out
  ethtool -K $dev esp-hw-offload off
  echo 0 > /sys/bus/netdevsim/del_device

Like these steps indicate, the NETIF_F_HW_ESP bit can be cleared after
xfrm_dev_state_add() acquired a reference to "struct net_device".
Also, xfrm_dev_state_add() does not check for the NETIF_F_HW_ESP bit
when acquiring a reference to "struct net_device".

Commit 03891f820c ("xfrm: handle NETDEV_UNREGISTER for xfrm device")
re-introduced the NETDEV_UNREGISTER event to xfrm_dev_event(), but that
commit for unknown reason chose to share xfrm_dev_down() between the
NETDEV_DOWN event and the NETDEV_UNREGISTER event.
I guess that that commit missed the behavior in the previous paragraph.

Therefore, we need to re-introduce xfrm_dev_unregister() in order to
release the reference to "struct net_device" by unconditionally flushing
state and policy.

Reported-by: syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84
Fixes: d77e38e612 ("xfrm: Add an IPsec hardware offloading API")
Cc: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:21:31 -05:00
arch arm64: hugetlbpage: avoid unused-but-set-parameter warning (gcc-16) 2026-03-04 07:21:30 -05:00
block block: decouple secure erase size limit from discard size limit 2026-03-04 07:20:56 -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 10:28:39 +01:00
Documentation ASoC: dt-bindings: asahi-kasei,ak5558: Fix the supply names 2026-03-04 07:20:48 -05:00
drivers ipmi: ipmb: initialise event handler read bytes 2026-03-04 07:21:31 -05:00
fs btrfs: replace BUG() with error handling in __btrfs_balance() 2026-03-04 07:21:29 -05:00
include include: uapi: netfilter_bridge.h: Cover for musl libc 2026-03-04 07:21:28 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/cancel: de-unionize file and user_data in struct io_cancel_data 2026-03-04 07:20:34 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-03-04 07:20:07 -05:00
kernel tracing: Fix false sharing in hwlat get_sample() 2026-03-04 07:21:21 -05:00
lib objpool: fix the overestimation of object pooling metadata size 2026-03-04 07:20:35 -05:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather 2026-02-19 16:29:55 +01:00
net xfrm: always flush state and policy upon NETDEV_UNREGISTER event 2026-03-04 07:21:31 -05:00
rust rust: rbtree: fix documentation typo in CursorMut peek_next method 2026-02-06 16:55:44 +01:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:14:50 +01:00
scripts modpost: Amend ppc64 save/restfpr symnames for -Os build 2026-03-04 07:21:09 -05:00
security apparmor: fix aa_label to return state from compount and component match 2026-03-04 07:20:41 -05:00
sound ALSA: usb-audio: Add sanity check for OOB writes at silencing 2026-03-04 07:21:29 -05:00
tools tools/power cpupower: Reset errno before strtoull() 2026-03-04 07:20:53 -05:00
usr kbuild: uapi: Strip comments before size type check 2025-11-13 15:34:35 -05:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:40:17 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.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 Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.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: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS gpiolib-acpi: Update file references in the Documentation and MAINTAINERS 2026-02-11 13:40:29 +01:00
Makefile kbuild: Add objtool to top-level clean target 2026-03-04 07:20:35 -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.