CVE-2021-46925— net/smc: fix kernel panic caused by race of smc_sock
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 smc_sock 竞争，导致内核恐慌。
Possible ATT&CK Techniques 2 AI
T1068 · Exploitation for Privilege Escalation T1499 · Endpoint Denial of ServiceAffected Version Matrix 8
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 5f08318f617b05b6ee389d8bd174c7af921ebf19< e8a5988a85c719ce7205cb00dcf0716dcf611332 |
affected |
5f08318f617b05b6ee389d8bd174c7af921ebf19< b85f751d71ae8e2a15e9bda98852ea9af35282eb |
affected | ||
5f08318f617b05b6ee389d8bd174c7af921ebf19< 349d43127dac00c15231e8ffbcaabd70f7b0e544 |
affected | ||
4.11 |
affected | ||
< 4.11 |
unaffected | ||
5.10.90≤ 5.10.* |
unaffected | ||
5.15.13≤ 5.15.* |
unaffected | ||
5.16≤ * |
unaffected |
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I. Basic Information for CVE-2021-46925
Vulnerability Information
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Vulnerability Title
net/smc: fix kernel panic caused by race of smc_sock
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix kernel panic caused by race of smc_sock
A crash occurs when smc_cdc_tx_handler() tries to access smc_sock
but smc_release() has already freed it.
[ 4570.695099] BUG: unable to handle page fault for address: 000000002eae9e88
[ 4570.696048] #PF: supervisor write access in kernel mode
[ 4570.696728] #PF: error_code(0x0002) - not-present page
[ 4570.697401] PGD 0 P4D 0
[ 4570.697716] Oops: 0002 [#1] PREEMPT SMP NOPTI
[ 4570.698228] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-rc4+ #111
[ 4570.699013] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 8c24b4c 04/0
[ 4570.699933] RIP: 0010:_raw_spin_lock+0x1a/0x30
<...>
[ 4570.711446] Call Trace:
[ 4570.711746] <IRQ>
[ 4570.711992] smc_cdc_tx_handler+0x41/0xc0
[ 4570.712470] smc_wr_tx_tasklet_fn+0x213/0x560
[ 4570.712981] ? smc_cdc_tx_dismisser+0x10/0x10
[ 4570.713489] tasklet_action_common.isra.17+0x66/0x140
[ 4570.714083] __do_softirq+0x123/0x2f4
[ 4570.714521] irq_exit_rcu+0xc4/0xf0
[ 4570.714934] common_interrupt+0xba/0xe0
Though smc_cdc_tx_handler() checked the existence of smc connection,
smc_release() may have already dismissed and released the smc socket
before smc_cdc_tx_handler() further visits it.
smc_cdc_tx_handler() |smc_release()
if (!conn) |
|
|smc_cdc_tx_dismiss_slots()
| smc_cdc_tx_dismisser()
|
|sock_put(&smc->sk) <- last sock_put,
| smc_sock freed
bh_lock_sock(&smc->sk) (panic) |
To make sure we won't receive any CDC messages after we free the
smc_sock, add a refcount on the smc_connection for inflight CDC
message(posted to the QP but haven't received related CQE), and
don't release the smc_connection until all the inflight CDC messages
haven been done, for both success or failed ones.
Using refcount on CDC messages brings another problem: when the link
is going to be destroyed, smcr_link_clear() will reset the QP, which
then remove all the pending CQEs related to the QP in the CQ. To make
sure all the CQEs will always come back so the refcount on the
smc_connection can always reach 0, smc_ib_modify_qp_reset() was replaced
by smc_ib_modify_qp_error().
And remove the timeout in smc_wr_tx_wait_no_pending_sends() since we
need to wait for all pending WQEs done, or we may encounter use-after-
free when handling CQEs.
For IB device removal routine, we need to wait for all the QPs on that
device been destroyed before we can destroy CQs on the device, or
the refcount on smc_connection won't reach 0 and smc_sock cannot be
released.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 smc_sock 竞争，导致内核恐慌。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2021-46925
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
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Other References for CVE-2021-46925 (3)
Same Patch Batch · Linux · 2024-02-27 · 67 CVEs total
| CVE-2021-46911 | 9.8 CRITICAL | ch_ktls: Fix kernel panic |
| CVE-2021-46955 | 8.2 HIGH | openvswitch: fix stack OOB read while fragmenting IPv4 packets |
| CVE-2021-46936 | 7.8 HIGH | net: fix use-after-free in tw_timer_handler |
| CVE-2021-46913 | 7.8 HIGH | netfilter: nftables: clone set element expression template |
| CVE-2021-46969 | 7.8 HIGH | bus: mhi: core: Fix invalid error returning in mhi_queue |
| CVE-2021-46973 | 7.8 HIGH | net: qrtr: Avoid potential use after free in MHI send |
| CVE-2021-46921 | 7.8 HIGH | locking/qrwlock: Fix ordering in queued_write_lock_slowpath() |
| CVE-2021-46967 | 7.8 HIGH | vhost-vdpa: fix vm_flags for virtqueue doorbell mapping |
| CVE-2021-46922 | 7.8 HIGH | KEYS: trusted: Fix TPM reservation for seal/unseal |
| CVE-2021-46963 | 7.8 HIGH | scsi: qla2xxx: Fix crash in qla2xxx_mqueuecommand() |
| CVE-2021-46929 | 7.8 HIGH | sctp: use call_rcu to free endpoint |
| CVE-2021-46958 | 7.8 HIGH | btrfs: fix race between transaction aborts and fsyncs leading to use-after-free |
| CVE-2021-46933 | 7.8 HIGH | usb: gadget: f_fs: Clear ffs_eventfd in ffs_data_clear. |
| CVE-2021-46948 | 7.5 HIGH | sfc: farch: fix TX queue lookup in TX event handling |
| CVE-2021-46960 | 7.5 HIGH | cifs: Return correct error code from smb2_get_enc_key |
| CVE-2021-46912 | 7.3 HIGH | net: Make tcp_allowed_congestion_control readonly in non-init netns |
| CVE-2021-46908 | 7.1 HIGH | bpf: Use correct permission flag for mixed signed bounds arithmetic |
| CVE-2021-46974 | 7.1 HIGH | bpf: Fix masking negation logic upon negative dst register |
| CVE-2021-46910 | 7.0 HIGH | ARM: 9063/1: mm: reduce maximum number of CPUs if DEBUG_KMAP_LOCAL is enabled |
| CVE-2021-46954 | net/sched: sch_frag: fix stack OOB read while fragmenting IPv4 packets |
Showing top 20 of 67 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
Same vendor: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
V. Comments for CVE-2021-46925
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