CVE-2025-39932: smb: client: let smbd_destroy() call disable_work_sync(&info->post_send_credits_work)

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-04 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: let smbd_destroy() call disable_work_sync(&info->post_send_credits_work) In smbd_destroy() we may destroy the memory so we better wait until post_send_credits_work is no longer pending and will never be started again. I actually just hit the case using rxe: WARNING: CPU: 0 PID: 138 at drivers/infiniband/sw/rxe/rxe_verbs.c:1032 rxe_post_recv+0x1ee/0x480 [rdma_rxe] ... [ 5305.686979] [ T138] smbd_post_recv+0x445/0xc10 [cifs] [ 5305.687135] [ T138] ? srso_alias_return_thunk+0x5/0xfbef5 [ 5305.687149] [ T138] ? __kasan_check_write+0x14/0x30 [ 5305.687185] [ T138] ? __pfx_smbd_post_recv+0x10/0x10 [cifs] [ 5305.687329] [ T138] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 5305.687356] [ T138] ? srso_alias_return_thunk+0x5/0xfbef5 [ 5305.687368] [ T138] ? srso_alias_return_thunk+0x5/0xfbef5 [ 5305.687378] [ T138] ? _raw_spin_unlock_irqrestore+0x11/0x60 [ 5305.687389] [ T138] ? srso_alias_return_thunk+0x5/0xfbef5 [ 5305.687399] [ T138] ? get_receive_buffer+0x168/0x210 [cifs] [ 5305.687555] [ T138] smbd_post_send_credits+0x382/0x4b0 [cifs] [ 5305.687701] [ T138] ? __pfx_smbd_post_send_credits+0x10/0x10 [cifs] [ 5305.687855] [ T138] ? __pfx___schedule+0x10/0x10 [ 5305.687865] [ T138] ? __pfx__raw_spin_lock_irq+0x10/0x10 [ 5305.687875] [ T138] ? queue_delayed_work_on+0x8e/0xa0 [ 5305.687889] [ T138] process_one_work+0x629/0xf80 [ 5305.687908] [ T138] ? srso_alias_return_thunk+0x5/0xfbef5 [ 5305.687917] [ T138] ? __kasan_check_write+0x14/0x30 [ 5305.687933] [ T138] worker_thread+0x87f/0x1570 ... It means rxe_post_recv was called after rdma_destroy_qp(). This happened because put_receive_buffer() was triggered by ib_drain_qp() and called: queue_work(info->workqueue, &info->post_send_credits_work);

Affected products

Linux kernel: from 4.16 before 6.12.49; from 6.13 before 6.16.9; 6.17-rc1, 6.17-rc2, 6.17-rc3, 6.17-rc4, 6.17-rc5, 6.17-rc6 — fixed in 6.12.49, 6.16.9
Linux: 4.16 — fixed in 6.17

How to fix

Upgrade to a fixed version: Linux kernel 6.12.49, 6.16.9; Linux 6.17. Check the vendor advisory for mitigations.

References

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