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00dc616e6c
[ Upstream commit 59b33fab4ca4d7dacc03367082777627e05d0323 ]
After commit 5c70eb5c593d ("net: better track kernel sockets lifetime"),
kernel sockets now use net_passive reference counting. However, commit
95d2b9f693ff ("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 ef7134c7fc48 ("smb: client: Fix use-after-free of network
namespace.") in v6.12 fixed the original netns UAF by manually
managing socket refcounts
- commit e9f2517a3e18 ("smb: client: fix TCP timers deadlock after
rmmod") in v6.13 attempted to use kernel sockets but introduced
TCP timer issues
- commit 5c70eb5c593d ("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 95d2b9f693ff ("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: 95d2b9f693ff ("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>
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 Restructured Text 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.