{ "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" } } ] } }