linux.git/drivers/net/caif, branch v6.12.80

serial: caif: hold tty->link reference in ldisc_open and ser_release

2026-03-25T10:08:27+00:00

[ Upstream commit 288598d80a068a0e9281de35bcb4ce495f189e2a ]

A reproducer triggers a KASAN slab-use-after-free in pty_write_room()
when caif_serial's TX path calls tty_write_room(). The faulting access
is on tty->link->port.

Hold an extra kref on tty->link for the lifetime of the caif_serial line
discipline: get it in ldisc_open() and drop it in ser_release(), and
also drop it on the ldisc_open() error path.

With this change applied, the reproducer no longer triggers the UAF in
my testing.

Link: https://gist.github.com/shuangpengbai/c898debad6bdf170a84be7e6b3d8707f
Link: https://lore.kernel.org/netdev/20260301220525.1546355-1-shuangpeng.kernel@gmail.com
Fixes: e31d5a05948e ("caif: tty's are kref objects so take a reference")
Signed-off-by: Shuangpeng Bai 
Reviewed-by: Jiayuan Chen 
Link: https://patch.msgid.link/20260306034006.3395740-1-shuangpeng.kernel@gmail.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

serial: caif: fix use-after-free in caif_serial ldisc_close()

2026-03-04T12:20:12+00:00

[ Upstream commit 308e7e4d0a846359685f40aade023aee7b27284c ]

There is a use-after-free bug in caif_serial where handle_tx() may
access ser->tty after the tty has been freed.

The race condition occurs between ldisc_close() and packet transmission:

    CPU 0 (close)                     CPU 1 (xmit)
    -------------                     ------------
    ldisc_close()
      tty_kref_put(ser->tty)
      [tty may be freed here]
                     <-- race window -->
                                      caif_xmit()
                                        handle_tx()
                                          tty = ser->tty  // dangling ptr
                                          tty->ops->write() // UAF!
      schedule_work()
        ser_release()
          unregister_netdevice()

The root cause is that tty_kref_put() is called in ldisc_close() while
the network device is still active and can receive packets.

Since ser and tty have a 1:1 binding relationship with consistent
lifecycles (ser is allocated in ldisc_open and freed in ser_release
via unregister_netdevice, and each ser binds exactly one tty), we can
safely defer the tty reference release to ser_release() where the
network device is unregistered.

Fix this by moving tty_kref_put() from ldisc_close() to ser_release(),
after unregister_netdevice(). This ensures the tty reference is held
as long as the network device exists, preventing the UAF.

Note: We save ser->tty before unregister_netdevice() because ser is
embedded in netdev's private data and will be freed along with netdev
(needs_free_netdev = true).

How to reproduce: Add mdelay(500) at the beginning of ldisc_close()
to widen the race window, then run the reproducer program [1].

Note: There is a separate deadloop issue in handle_tx() when using
PORT_UNKNOWN serial ports (e.g., /dev/ttyS3 in QEMU without proper
serial backend). This deadloop exists even without this patch,
and is likely caused by inconsistency between uart_write_room() and
uart_write() in serial core. It has been addressed in a separate
patch [2].

KASAN report:

==================================================================
BUG: KASAN: slab-use-after-free in handle_tx+0x5d1/0x620
Read of size 1 at addr ffff8881131e1490 by task caif_uaf_trigge/9929

Call Trace:
 
 dump_stack_lvl+0x10e/0x1f0
 print_report+0xd0/0x630
 kasan_report+0xe4/0x120
 handle_tx+0x5d1/0x620
 dev_hard_start_xmit+0x9d/0x6c0
 __dev_queue_xmit+0x6e2/0x4410
 packet_xmit+0x243/0x360
 packet_sendmsg+0x26cf/0x5500
 __sys_sendto+0x4a3/0x520
 __x64_sys_sendto+0xe0/0x1c0
 do_syscall_64+0xc9/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f615df2c0d7

Allocated by task 9930:

Freed by task 64:

Last potentially related work creation:

The buggy address belongs to the object at ffff8881131e1000
 which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 1168 bytes inside of
 freed 2048-byte region [ffff8881131e1000, ffff8881131e1800)

The buggy address belongs to the physical page:
page_owner tracks the page as allocated
page last free pid 9778 tgid 9778 stack trace:

Memory state around the buggy address:
 ffff8881131e1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881131e1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881131e1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8881131e1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881131e1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
[1]: https://gist.github.com/mrpre/f683f244544f7b11e7fa87df9e6c2eeb
[2]: https://lore.kernel.org/linux-serial/20260204074327.226165-1-jiayuan.chen@linux.dev/T/#u

Reported-by: syzbot+827272712bd6d12c79a4@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000a4a7550611e234f5@google.com/T/
Fixes: 56e0ef527b18 ("drivers/net: caif: fix wrong rtnl_is_locked() usage")
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Jiayuan Chen 
Reviewed-by: Jijie Shao 
Link: https://patch.msgid.link/20260206074450.154267-1-jiayuan.chen@linux.dev
Signed-off-by: Paolo Abeni 
Signed-off-by: Sasha Levin

caif_virtio: fix wrong pointer check in cfv_probe()

2025-03-13T12:02:04+00:00

[ Upstream commit a466fd7e9fafd975949e5945e2f70c33a94b1a70 ]

del_vqs() frees virtqueues, therefore cfv->vq_tx pointer should be checked
for NULL before calling it, not cfv->vdev. Also the current implementation
is redundant because the pointer cfv->vdev is dereferenced before it is
checked for NULL.

Fix this by checking cfv->vq_tx for NULL instead of cfv->vdev before
calling del_vqs().

Fixes: 0d2e1a2926b1 ("caif_virtio: Introduce caif over virtio")
Signed-off-by: Vitaliy Shevtsov 
Reviewed-by: Gerhard Engleder 
Link: https://patch.msgid.link/20250227184716.4715-1-v.shevtsov@mt-integration.ru
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

caif_virtio: use virtio_find_single_vq() for single virtqueue finding

2024-07-17T09:20:56+00:00

Since caif uses only one queue, convert to virtio_find_single_vq()
helper which is made for this purpose.

Signed-off-by: Jiri Pirko 
Message-Id: <20240708074814.1739223-2-jiri@resnulli.us>
Signed-off-by: Michael S. Tsirkin

net: caif: virtio: drop owner assignment

2024-05-22T12:31:17+00:00

virtio core already sets the .owner, so driver does not need to.

Signed-off-by: Krzysztof Kozlowski 

Message-Id: <20240331-module-owner-virtio-v2-16-98f04bfaf46a@linaro.org>
Signed-off-by: Michael S. Tsirkin

tty: use u8 for flags

2023-08-11T19:12:45+00:00

This makes all those 'char's an explicit 'u8'. This is part of the
continuing unification of chars and flags to be consistent u8.

This approaches tty_port_default_receive_buf().

Note that we do not change signedness as we compile with
-funsigned-char.

Signed-off-by: "Jiri Slaby (SUSE)" 
Cc: William Hubbs 
Cc: Chris Brannon 
Cc: Kirk Reiser 
Cc: Samuel Thibault 
Cc: Marcel Holtmann 
Cc: Johan Hedberg 
Cc: Luiz Augusto von Dentz 
Cc: Dmitry Torokhov 
Cc: Arnd Bergmann 
Cc: "David S. Miller" 
Cc: Eric Dumazet 
Cc: Jakub Kicinski 
Cc: Paolo Abeni 
Cc: Max Staudt 
Cc: Wolfgang Grandegger 
Cc: Marc Kleine-Budde 
Cc: Dario Binacchi 
Cc: Andreas Koensgen 
Cc: Jeremy Kerr 
Cc: Matt Johnston 
Cc: Krzysztof Kozlowski 
Cc: Liam Girdwood 
Cc: Mark Brown 
Cc: Jaroslav Kysela 
Cc: Takashi Iwai 
Acked-by: Mark Brown 
Link: https://lore.kernel.org/r/20230810091510.13006-18-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

tty: make tty_ldisc_ops::buf() hooks operate on size_t

2023-08-11T19:12:45+00:00

Count passed to tty_ldisc_ops::receive_buf*(), ::lookahead_buf(), and
returned from ::receive_buf2() is expected to be size_t. So set it to
size_t to unify with the rest of the code.

Signed-off-by: "Jiri Slaby (SUSE)" 
Cc: William Hubbs 
Cc: Chris Brannon 
Cc: Kirk Reiser 
Cc: Samuel Thibault 
Cc: Marcel Holtmann 
Cc: Johan Hedberg 
Cc: Luiz Augusto von Dentz 
Cc: Dmitry Torokhov 
Cc: Arnd Bergmann 
Cc: "David S. Miller" 
Cc: Eric Dumazet 
Cc: Jakub Kicinski 
Cc: Paolo Abeni 
Cc: Max Staudt 
Cc: Wolfgang Grandegger 
Cc: Marc Kleine-Budde 
Cc: Dario Binacchi 
Cc: Andreas Koensgen 
Cc: Jeremy Kerr 
Cc: Matt Johnston 
Cc: Krzysztof Kozlowski 
Cc: Liam Girdwood 
Cc: Mark Brown 
Cc: Jaroslav Kysela 
Cc: Takashi Iwai 
Acked-by: Mark Brown 
Link: https://lore.kernel.org/r/20230810091510.13006-16-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

caif_virtio: fix race between virtio_device_ready() and ndo_open()

2022-06-27T12:04:30+00:00

We currently depend on probe() calling virtio_device_ready() -
which happens after netdev
registration. Since ndo_open() can be called immediately
after register_netdev, this means there exists a race between
ndo_open() and virtio_device_ready(): the driver may start to use the
device (e.g. TX) before DRIVER_OK which violates the spec.

Fix this by switching to use register_netdevice() and protect the
virtio_device_ready() with rtnl_lock() to make sure ndo_open() can
only be called after virtio_device_ready().

Fixes: 0d2e1a2926b18 ("caif_virtio: Introduce caif over virtio")
Signed-off-by: Jason Wang 
Message-Id: <20220620051115.3142-3-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin

caif_virtio: switch to netif_napi_add_weight()

2022-05-08T10:33:57+00:00

caif_virtio uses a custom napi weight, switch to the new
API for setting custom weights.

Signed-off-by: Jakub Kicinski 
Acked-by: Michael S. Tsirkin 
Signed-off-by: David S. Miller

net: caif: Use netif_rx().

2022-03-04T12:02:19+00:00

Since commit
   baebdf48c3600 ("net: dev: Makes sure netif_rx() can be invoked in any context.")

the function netif_rx() can be used in preemptible/thread context as
well as in interrupt context.

Use netif_rx().

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: David S. Miller