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95d2b9f693
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Kuniyuki Iwashima 95d2b9f693 Revert "smb: client: fix TCP timers deadlock after rmmod" 
This reverts commit e9f2517a3e.

Commit e9f2517a3e ("smb: client: fix TCP timers deadlock after
rmmod") is intended to fix a null-ptr-deref in LOCKDEP, which is
mentioned as CVE-2024-54680, but is actually did not fix anything;
The issue can be reproduced on top of it. [0]

Also, it reverted the change by commit ef7134c7fc ("smb: client:
Fix use-after-free of network namespace.") and introduced a real
issue by reviving the kernel TCP socket.

When a reconnect happens for a CIFS connection, the socket state
transitions to FIN_WAIT_1.  Then, inet_csk_clear_xmit_timers_sync()
in tcp_close() stops all timers for the socket.

If an incoming FIN packet is lost, the socket will stay at FIN_WAIT_1
forever, and such sockets could be leaked up to net.ipv4.tcp_max_orphans.

Usually, FIN can be retransmitted by the peer, but if the peer aborts
the connection, the issue comes into reality.

I warned about this privately by pointing out the exact report [1],
but the bogus fix was finally merged.

So, we should not stop the timers to finally kill the connection on
our side in that case, meaning we must not use a kernel socket for
TCP whose sk->sk_net_refcnt is 0.

The kernel socket does not have a reference to its netns to make it
possible to tear down netns without cleaning up every resource in it.

For example, tunnel devices use a UDP socket internally, but we can
destroy netns without removing such devices and let it complete
during exit.  Otherwise, netns would be leaked when the last application
died.

However, this is problematic for TCP sockets because TCP has timers to
close the connection gracefully even after the socket is close()d.  The
lifetime of the socket and its netns is different from the lifetime of
the underlying connection.

If the socket user does not maintain the netns lifetime, the timer could
be fired after the socket is close()d and its netns is freed up, resulting
in use-after-free.

Actually, we have seen so many similar issues and converted such sockets
to have a reference to netns.

That's why I converted the CIFS client socket to have a reference to
netns (sk->sk_net_refcnt == 1), which is somehow mentioned as out-of-scope
of CIFS and technically wrong in e9f2517a3e, but **is in-scope and right
fix**.

Regarding the LOCKDEP issue, we can prevent the module unload by
bumping the module refcount when switching the LOCKDDEP key in
sock_lock_init_class_and_name(). [2]

For a while, let's revert the bogus fix.

Note that now we can use sk_net_refcnt_upgrade() for the socket
conversion, but I'll do so later separately to make backport easy.

Link: https://lore.kernel.org/all/20250402020807.28583-1-kuniyu@amazon.com/ #[0]
Link: https://lore.kernel.org/netdev/c08bd5378da647a2a4c16698125d180a@huawei.com/ #[1]
Link: https://lore.kernel.org/lkml/20250402005841.19846-1-kuniyu@amazon.com/ #[2]
Fixes: e9f2517a3e ("smb: client: fix TCP timers deadlock after rmmod")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
2025-04-13 17:24:55 -05:00
arch bpf-fixes 2025-04-12 12:48:10 -07:00
block treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push fixes reverts the multibuffer hash testing as it is buggy. 2025-04-02 09:14:59 -07:00
Documentation A few more miscellaneous ext4 bug fixes and cleanups including some 2025-04-13 07:15:50 -07:00
drivers pwm: A set of fixes for pwm core and various drivers 2025-04-12 08:11:19 -07:00
fs Revert "smb: client: fix TCP timers deadlock after rmmod" 2025-04-13 17:24:55 -05:00
include drm fixes for 6.15-rc2 2025-04-10 20:30:06 -07:00
init Miscellaneous scheduler fixes/updates: 2025-04-06 10:44:58 -07:00
io_uring io_uring/kbuf: reject zero sized provided buffers 2025-04-07 07:51:23 -06:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel tracing fixes for v6.15 2025-04-12 15:37:40 -07:00
lib CRC cleanups for 6.15 2025-04-08 12:09:28 -07:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm Disable SLUB_TINY for build testing 2025-04-06 10:00:04 -07:00
net bpf-fixes 2025-04-12 12:48:10 -07:00
rust Kbuild updates for v6.15 2025-04-05 15:46:50 -07:00
samples treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
scripts Disable SLUB_TINY for build testing 2025-04-06 10:00:04 -07:00
security mseal sysmap: kernel config and header change 2025-04-01 15:17:14 -07:00
sound soundwire fix for 6.15-rc1 2025-04-06 12:04:53 -07:00
tools memblock: fix build of memblock test 2025-04-13 07:11:33 -07:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-05 04:06:45 +09:00
virt ARM: 2025-04-08 13:47:55 -07:00
.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 2025-01-10 00:17:25 +01:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: Create intermediate vmlinux build with relocations preserved 2025-03-17 00:29:50 +09:00
.mailmap mailmap: add an entry for Nicolas Schier 2025-04-01 15:20:45 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS Including fixes from netfilter. 2025-04-04 09:15:35 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS MAINTAINERS: add more keywords for the GPIO subsystem entry 2025-04-08 10:41:58 +02:00
Makefile Linux 6.15-rc2 2025-04-13 11:54:49 -07:00
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.