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Wang Zhaolong 5a9c806567 smb: client: fix netns refcount leak after net_passive changes 
[ Upstream commit 59b33fab4c ]

After commit 5c70eb5c59 ("net: better track kernel sockets lifetime"),
kernel sockets now use net_passive reference counting. However, commit
95d2b9f693 ("Revert "smb: client: fix TCP timers deadlock after rmmod"")
restored the manual socket refcount manipulation without adapting to this
new mechanism, causing a memory leak.

The issue can be reproduced by[1]:
1. Creating a network namespace
2. Mounting and Unmounting CIFS within the namespace
3. Deleting the namespace

Some memory leaks may appear after a period of time following step 3.

unreferenced object 0xffff9951419f6b00 (size 256):
  comm "ip", pid 447, jiffies 4294692389 (age 14.730s)
  hex dump (first 32 bytes):
    1b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 80 77 c2 44 51 99 ff ff  .........w.DQ...
  backtrace:
    __kmem_cache_alloc_node+0x30e/0x3d0
    __kmalloc+0x52/0x120
    net_alloc_generic+0x1d/0x30
    copy_net_ns+0x86/0x200
    create_new_namespaces+0x117/0x300
    unshare_nsproxy_namespaces+0x60/0xa0
    ksys_unshare+0x148/0x360
    __x64_sys_unshare+0x12/0x20
    do_syscall_64+0x59/0x110
    entry_SYSCALL_64_after_hwframe+0x78/0xe2
...
unreferenced object 0xffff9951442e7500 (size 32):
  comm "mount.cifs", pid 475, jiffies 4294693782 (age 13.343s)
  hex dump (first 32 bytes):
    40 c5 38 46 51 99 ff ff 18 01 96 42 51 99 ff ff  @.8FQ......BQ...
    01 00 00 00 6f 00 c5 07 6f 00 d8 07 00 00 00 00  ....o...o.......
  backtrace:
    __kmem_cache_alloc_node+0x30e/0x3d0
    kmalloc_trace+0x2a/0x90
    ref_tracker_alloc+0x8e/0x1d0
    sk_alloc+0x18c/0x1c0
    inet_create+0xf1/0x370
    __sock_create+0xd7/0x1e0
    generic_ip_connect+0x1d4/0x5a0 [cifs]
    cifs_get_tcp_session+0x5d0/0x8a0 [cifs]
    cifs_mount_get_session+0x47/0x1b0 [cifs]
    dfs_mount_share+0xfa/0xa10 [cifs]
    cifs_mount+0x68/0x2b0 [cifs]
    cifs_smb3_do_mount+0x10b/0x760 [cifs]
    smb3_get_tree+0x112/0x2e0 [cifs]
    vfs_get_tree+0x29/0xf0
    path_mount+0x2d4/0xa00
    __se_sys_mount+0x165/0x1d0

Root cause:
When creating kernel sockets, sk_alloc() calls net_passive_inc() for
sockets with sk_net_refcnt=0. The CIFS code manually converts kernel
sockets to user sockets by setting sk_net_refcnt=1, but doesn't call
the corresponding net_passive_dec(). This creates an imbalance in the
net_passive counter, which prevents the network namespace from being
destroyed when its last user reference is dropped. As a result, the
entire namespace and all its associated resources remain allocated.

Timeline of patches leading to this issue:
- commit ef7134c7fc ("smb: client: Fix use-after-free of network
  namespace.") in v6.12 fixed the original netns UAF by manually
  managing socket refcounts
- commit e9f2517a3e ("smb: client: fix TCP timers deadlock after
  rmmod") in v6.13 attempted to use kernel sockets but introduced
  TCP timer issues
- commit 5c70eb5c59 ("net: better track kernel sockets lifetime")
  in v6.14-rc5 introduced the net_passive mechanism with
  sk_net_refcnt_upgrade() for proper socket conversion
- commit 95d2b9f693 ("Revert "smb: client: fix TCP timers deadlock
  after rmmod"") in v6.15-rc3 reverted to manual refcount management
  without adapting to the new net_passive changes

Fix this by using sk_net_refcnt_upgrade() which properly handles the
net_passive counter when converting kernel sockets to user sockets.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=220343 [1]
Fixes: 95d2b9f693 ("Revert "smb: client: fix TCP timers deadlock after rmmod"")
Cc: stable@vger.kernel.org
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Wang Zhaolong <wangzhaolong@huaweicloud.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-08-20 18:30:57 +02:00
arch mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() 2025-08-20 18:30:55 +02:00
block block: Introduce bio_needs_zone_write_plugging() 2025-08-20 18:30:51 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: jitter - fix intermediary handling 2025-08-20 18:30:42 +02:00
Documentation Documentation: ACPI: Fix parent device references 2025-08-20 18:30:15 +02:00
drivers mfd: cros_ec: Separate charge-control probing from USB-PD 2025-08-20 18:30:56 +02:00
fs
include net: better track kernel sockets lifetime 2025-08-20 18:30:56 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 12:13:32 +02:00
io_uring io_uring/poll: fix POLLERR handling 2025-07-24 08:56:23 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel printk: nbcon: Allow reacquire during panic 2025-08-20 18:30:47 +02:00
lib lib/sbitmap: convert shallow_depth from one word to the whole sbitmap 2025-08-20 18:30:49 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock 2025-08-20 18:30:55 +02:00
net net: better track kernel sockets lifetime 2025-08-20 18:30:56 +02:00
rust rust: use #[used(compiler)] to fix build and modpost with Rust >= 1.89.0 2025-07-24 08:56:37 +02:00
samples samples: mei: Fix building on musl libc 2025-08-15 12:13:38 +02:00
scripts kconfig: lxdialog: fix 'space' to (de)select options 2025-08-20 18:30:48 +02:00
security apparmor: fix x_table_lookup when stacking is not the first entry 2025-08-20 18:30:47 +02:00
sound ASoC: fsl_sai: replace regmap_write with regmap_update_bits 2025-08-20 18:30:50 +02:00
tools tools/hv: fcopy: Fix irregularities with size of ring buffer 2025-08-20 18:30:56 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.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 MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.42 2025-08-15 12:14:14 +02:00
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.