kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-11-10 20:48:12 +00:00
Code Issues Releases Packages Activity
No description
1,325,711 commits 117 branches 5,827 tags 6.3 GiB
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Jiayuan Chen 52731ef443 serial: caif: fix use-after-free in caif_serial ldisc_close() 
[ Upstream commit 308e7e4d0a ]

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:
 <TASK>
 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: 56e0ef527b ("drivers/net: caif: fix wrong rtnl_is_locked() usage")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Reviewed-by: Jijie Shao <shaojijie@huawei.com>
Link: https://patch.msgid.link/20260206074450.154267-1-jiayuan.chen@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:20:12 -05:00
arch arm64: dts: qcom: sm6115: Add CX_MEM/DBGC GPU regions 2026-03-04 07:19:47 -05:00
block block: add a bio_add_virt_nofail helper 2026-03-04 07:19:26 -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 Documentation: tracing: Add PCI tracepoint documentation 2026-03-04 07:19:59 -05:00
drivers serial: caif: fix use-after-free in caif_serial ldisc_close() 2026-03-04 07:20:12 -05:00
fs smb: client: correct value for smbd_max_fragmented_recv_size 2026-03-04 07:20:11 -05:00
include net: Add skb_dstref_steal and skb_dstref_restore 2026-03-04 07:20:11 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/sync: validate passed in offset 2026-03-04 07:19:28 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-03-04 07:20:07 -05:00
kernel ucount: check for CAP_SYS_RESOURCE using ns_capable_noaudit() 2026-03-04 07:20:08 -05:00
lib procfs: avoid fetching build ID while holding VMA lock 2026-02-11 13:40:18 +01:00
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: fix ip_rt_bug race in icmp_route_lookup reverse path 2026-03-04 07:20:12 -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 scripts: generate_rust_analyzer: Add compiler_builtins -> core dep 2026-02-06 16:55:47 +01:00
security evm: Use ordered xattrs list to calculate HMAC in evm_init_hmac() 2026-03-04 07:19:56 -05:00
sound ASoC: nau8821: Fixup nau8821_enable_jack_detect() 2026-03-04 07:19:52 -05:00
tools selftests/mm: convert page_size to unsigned long 2026-03-04 07:20:07 -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 Linux 6.12.74 2026-02-19 16:29:56 +01:00
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.