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vuln-cve/data/2024/56xxx/CVE-2024-56640.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2024-56640",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2024-12-27T15:00:39.839Z",
"datePublished": "2024-12-27T15:02:42.253Z",
"dateUpdated": "2026-08-05T11:45:38.986Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-08-05T11:45:38.986Z"
},
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix LGR and link use-after-free issue\n\nWe encountered a LGR/link use-after-free issue, which manifested as\nthe LGR/link refcnt reaching 0 early and entering the clear process,\nmaking resource access unsafe.\n\n refcount_t: addition on 0; use-after-free.\n WARNING: CPU: 14 PID: 107447 at lib/refcount.c:25 refcount_warn_saturate+0x9c/0x140\n Workqueue: events smc_lgr_terminate_work [smc]\n Call trace:\n refcount_warn_saturate+0x9c/0x140\n __smc_lgr_terminate.part.45+0x2a8/0x370 [smc]\n smc_lgr_terminate_work+0x28/0x30 [smc]\n process_one_work+0x1b8/0x420\n worker_thread+0x158/0x510\n kthread+0x114/0x118\n\nor\n\n refcount_t: underflow; use-after-free.\n WARNING: CPU: 6 PID: 93140 at lib/refcount.c:28 refcount_warn_saturate+0xf0/0x140\n Workqueue: smc_hs_wq smc_listen_work [smc]\n Call trace:\n refcount_warn_saturate+0xf0/0x140\n smcr_link_put+0x1cc/0x1d8 [smc]\n smc_conn_free+0x110/0x1b0 [smc]\n smc_conn_abort+0x50/0x60 [smc]\n smc_listen_find_device+0x75c/0x790 [smc]\n smc_listen_work+0x368/0x8a0 [smc]\n process_one_work+0x1b8/0x420\n worker_thread+0x158/0x510\n kthread+0x114/0x118\n\nIt is caused by repeated release of LGR/link refcnt. One suspect is that\nsmc_conn_free() is called repeatedly because some smc_conn_free() from\nserver listening path are not protected by sock lock.\n\ne.g.\n\nCalls under socklock | smc_listen_work\n-------------------------------------------------------\nlock_sock(sk) | smc_conn_abort\nsmc_conn_free | \\- smc_conn_free\n\\- smcr_link_put | \\- smcr_link_put (duplicated)\nrelease_sock(sk)\n\nSo here add sock lock protection in smc_listen_work() path, making it\nexclusive with other connection operations."
}
],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"baseScore": 9.8,
"baseSeverity": "CRITICAL"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug is in `smc_listen_work()`, the SMC server-side CLC handshake worker that is queued from `smc_tcp_listen_work()` for every inbound TCP connection carrying the SMC option, and it processes CLC Proposal/Confirm/Decline messages sent by the remote peer over routable TCP/IP. A remote host that can reach an AF_SMC listener drives the entire vulnerable path.\nAC:L - The attacker controls both sides of the race: `smc_clc_wait_msg()` (net/smc/smc_clc.c:784-794) accepts a CLC DECLINE at any point, and with the attacker-chosen `SMC_FIRST_CONTACT_MASK` bit set it calls `smc_lgr_terminate_sched()`, scheduling `__smc_lgr_terminate()` (which takes lock_sock and frees conn state) concurrently with the unlocked `smc_listen_work()` → `smc_conn_abort()` → `smc_conn_free()` path, whose `conn->freed` guard is an unsynchronized bitfield. The attacker can open unlimited parallel connections into the same link group on the separate `smc_hs_wq` and retry indefinitely at no cost.\nPR:N - The CLC handshake in `smc_listen_work()` runs entirely before any application-level authentication and requires no credentials — the attacker only needs to complete a TCP connection to the SMC listener. No capability, namespace, or local account is involved.\nUI:N - The listen worker is queued automatically from the TCP accept path by `smc_clcsock_data_ready()`/`smc_tcp_listen_work()`; no action by the local user or administrator is needed beyond running the SMC server that is already listening.\nS:U - The corruption is confined to kernel heap objects (`struct smc_link_group`, `struct smc_link`) within the same kernel security authority, with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - The duplicate `smcr_link_put()`/`smc_lgr_put()` drives the refcounts to zero early, so the `kzalloc`'d `struct smc_link_group` is `kfree()`d while `__smc_lgr_terminate()`, `smc_listen_work()`, and the LLC/CDC paths still dereference it — a classic use-after-free read of a generic kmalloc slab object that an attacker can reallocate and shape, leaking link-group state including `peer_systemid` and RDMA `rtokens` (remote keys/addresses).\nI:H - Post-free writes into the reallocated object include `lgr->sync_err`/`terminating` bitfields, `refcount_inc()`, and list/rb-tree manipulation, while the freed structure embeds `struct work_struct terminate_work`, `struct delayed_work free_work`, and per-link `link_down_wrk` — function pointers that `schedule_work()`/`smc_lgr_schedule_free_work()` will subsequently invoke, giving a heap-spray path to control-flow hijack.\nA:H - The commit documents real production `refcount_t: underflow`/`addition on 0` warnings in `smcr_link_put()` and `__smc_lgr_terminate()`; refcount saturation plus use of freed link-group memory yields oopses and kernel panics, and the condition is remotely and repeatably triggerable."
}
]
}
],
"affected": [
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"net/smc/af_smc.c"
],
"versions": [
{
"version": "3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8",
"lessThan": "f502a88fdd415647a1f2dc45fac71b9c522a052b",
"status": "affected",
"versionType": "git"
},
{
"version": "3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8",
"lessThan": "0cf598548a6c36d90681d53c6b77d52363f2f295",
"status": "affected",
"versionType": "git"
},
{
"version": "3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8",
"lessThan": "673d606683ac70bc074ca6676b938bff18635226",
"status": "affected",
"versionType": "git"
},
{
"version": "3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8",
"lessThan": "6f0ae06a234a78ae137064f2c89135ac078a00eb",
"status": "affected",
"versionType": "git"
},
{
"version": "3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8",
"lessThan": "2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7",
"status": "affected",
"versionType": "git"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"net/smc/af_smc.c"
],
"versions": [
{
"version": "4.18",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.18",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.15.174",
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.1.120",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.6.66",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.12.5",
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.13",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.18",
"versionEndExcluding": "5.15.174"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.18",
"versionEndExcluding": "6.1.120"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.18",
"versionEndExcluding": "6.6.66"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.18",
"versionEndExcluding": "6.12.5"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.18",
"versionEndExcluding": "6.13"
}
]
}
]
}
],
"references": [
{
"url": "https://git.kernel.org/stable/c/f502a88fdd415647a1f2dc45fac71b9c522a052b"
},
{
"url": "https://git.kernel.org/stable/c/0cf598548a6c36d90681d53c6b77d52363f2f295"
},
{
"url": "https://git.kernel.org/stable/c/673d606683ac70bc074ca6676b938bff18635226"
},
{
"url": "https://git.kernel.org/stable/c/6f0ae06a234a78ae137064f2c89135ac078a00eb"
},
{
"url": "https://git.kernel.org/stable/c/2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7"
}
],
"title": "net/smc: fix LGR and link use-after-free issue",
"x_generator": {
"engine": "bippy-1.2.0"
}
},
"adp": [
{
"metrics": [
{
"cvssV3_1": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.8,
"attackVector": "LOCAL",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
}
},
{
"other": {
"type": "ssvc",
"content": {
"id": "CVE-2024-56640",
"role": "CISA Coordinator",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"version": "2.0.3",
"timestamp": "2025-02-11T15:41:51.231757Z"
}
}
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"type": "CWE",
"cweId": "CWE-416",
"description": "CWE-416 Use After Free"
}
]
}
],
"title": "CISA ADP Vulnrichment",
"providerMetadata": {
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP",
"dateUpdated": "2025-02-11T15:45:22.074Z"
}
},
{
"title": "CVE Program Container",
"references": [
{
"url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html"
}
],
"providerMetadata": {
"orgId": "af854a3a-2127-422b-91ae-364da2661108",
"shortName": "CVE",
"dateUpdated": "2025-11-03T20:51:40.000Z"
}
}
]
}
}