{"id":"AZL-55527","summary":"CVE-2024-56640 affecting package kernel for versions less than 6.6.76.1-1","details":"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.","modified":"2026-04-01T05:18:38.873011Z","published":"2024-12-27T15:15:23Z","upstream":["CVE-2024-56640"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-56640"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.76.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-55527.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}