{"id":"CVE-2026-80981","state":"PUBLISHED","title":"net/smc: fix use-after-free of the LLC qentry in smc_llc_srv_add_link()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix use-after-free of the LLC qentry in smc_llc_srv_add_link()\n\nsmc_llc_srv_add_link() keeps add_llc pointing into the queue entry:\n\n  add_llc = &qentry->msg.add_link;\t\t\tsmc_llc.c:1482\n  ...\n  smc_llc_save_add_link_info(link_new, add_llc);\tsmc_llc.c:1494\n  smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);\t\tsmc_llc.c:1495\n  ...\n  u8 *llc_msg = smc_link_shared_v2_rxbuf(link) ?\n\t(u8 *)lgr->wr_rx_buf_v2 : (u8 *)add_llc;\tsmc_llc.c:1504\n  smc_llc_save_add_link_rkeys(link, link_new, llc_msg);\tsmc_llc.c:1506\n\nsmc_llc_flow_qentry_del() kfree()s the entry, so on a link without a shared\nv2 receive buffer the pointer handed to smc_llc_save_add_link_rkeys() is\nalready freed. Before the Fixes: commit that branch always used\nlgr->wr_rx_buf_v2 and add_llc was not used after the free.\n\nReproduced on an unpatched tree over rxe, with KASAN, kasan_multi_shot\nand a link forced to max_recv_sge == 1: the entry is freed and read by\nthe same call, and the freeing frame is smc_llc_srv_add_link() itself.\n\n  [    2.523161] BUG: KASAN: slab-use-after-free in smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523499] Read of size 2 at addr ffff8880052194de by task kworker/0:1/11\n  [    2.523789]\n  [    2.523862] CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 7.2.0-rc5-p0-g2c9dd296545d #35 PREEMPT(lazy)\n  [    2.523865] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n  [    2.523866] Workqueue: smc_hs_wq smc_listen_work\n  [    2.523869] Call Trace:\n  [    2.523870]  <TASK>\n  [    2.523871]  dump_stack_lvl+0x53/0x70\n  [    2.523872]  print_report+0xd0/0x630\n  [    2.523874]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10\n  [    2.523876]  ? smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523878]  kasan_report+0xce/0x100\n  [    2.523879]  ? smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523881]  smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523883]  ? smcr_buf_reg_lgr+0x2a4/0x660\n  [    2.523885]  smc_llc_srv_add_link+0xaa2/0x1e50\n  [    2.523888]  ? _printk+0xba/0xf0\n  [    2.523897]  ? __pfx_smc_llc_srv_add_link+0x10/0x10\n  [    2.523899]  ? down_write+0xb0/0x130\n  [    2.523903]  ? __pfx_down_write+0x10/0x10\n  [    2.523905]  smc_listen_work+0x489e/0x4d00\n  [    2.523907]  ? kmem_cache_free+0x1c6/0x3a0\n  [    2.523911]  ? __pfx_smc_listen_work+0x10/0x10\n  [    2.523913]  ? release_sock+0x148/0x1d0\n  [    2.523915]  ? smc_tcp_listen_work+0xb4f/0xfc0\n  [    2.523917]  ? _raw_spin_lock_irq+0x80/0xe0\n  [    2.523918]  ? __pfx__raw_spin_lock_irq+0x10/0x10\n  [    2.523920]  process_one_work+0x633/0x1030\n  [    2.523922]  ? assign_work+0x11d/0x370\n  [    2.523924]  worker_thread+0x45b/0xd10\n  [    2.523926]  ? __pfx_worker_thread+0x10/0x10\n  [    2.523928]  ? __pfx_worker_thread+0x10/0x10\n  [    2.523929]  kthread+0x2c6/0x3b0\n  [    2.523931]  ? recalc_sigpending+0x15c/0x1e0\n  [    2.523934]  ? __pfx_kthread+0x10/0x10\n  [    2.523935]  ret_from_fork+0x36e/0x5a0\n  [    2.523937]  ? __pfx_ret_from_fork+0x10/0x10\n  [    2.523938]  ? __switch_to+0x572/0xdd0\n  [    2.523943]  ? __pfx_kthread+0x10/0x10\n  [    2.523944]  ret_from_fork_asm+0x1a/0x30\n  [    2.523947]  </TASK>\n  [    2.523948]\n  [    2.531253] Allocated by task 48:\n  [    2.531399]  kasan_save_stack+0x33/0x60\n  [    2.531570]  kasan_save_track+0x14/0x30\n  [    2.531737]  __kasan_kmalloc+0x8f/0xa0\n  [    2.531905]  __kmalloc_cache_noprof+0x158/0x370\n  [    2.532100]  smc_llc_enqueue+0x72/0x560\n  [    2.532268]  smc_wr_rx_tasklet_fn+0x474/0xa80\n  [    2.532491]  tasklet_action_common+0x20f/0x8a0\n  [    2.532714]  handle_softirqs+0x18e/0x590\n  [    2.532886]  do_softirq+0x3b/0x60\n  [    2.533036]  __local_bh_enable_ip+0x61/0x70\n  [    2.533221]  __alloc_skb+0x732/0x890\n  [    2.533384]  rxe_init_packet+0x16b/0x4f0\n  [    2.533567]  prepare_ack_packet+0xb8/0x830\n  [    2.533760]  rxe_receiver+0x495/0x96e0\n  [    2.533933]  do_work+0x144/0x470\n  [    2\n---truncated---","publishedAt":"2026-09-11T19:42:41.543Z","updatedAt":"2026-10-19T08:46:05.740Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"27ef6a9981fe74191849966a6d5e0400a4008ab8","status":"affected","lessThan":"c52a998a223e7e84333306996edec096178d1e95","versionType":"git"},{"version":"27ef6a9981fe74191849966a6d5e0400a4008ab8","status":"affected","lessThan":"adef84cc85d449ac28d2b4b4c49cf19619c56e27","versionType":"git"},{"version":"27ef6a9981fe74191849966a6d5e0400a4008ab8","status":"affected","lessThan":"a42a459ef0e54cb0c4b3e43e21cb0e658e664f64","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_llc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_llc.c"]}],"references":["https://git.kernel.org/stable/c/c52a998a223e7e84333306996edec096178d1e95","https://git.kernel.org/stable/c/adef84cc85d449ac28d2b4b4c49cf19619c56e27","https://git.kernel.org/stable/c/a42a459ef0e54cb0c4b3e43e21cb0e658e664f64"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/80xxx/CVE-2026-80981.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80981","state":"PUBLISHED","datePublished":"2026-09-11T19:42:41.543Z","dateUpdated":"2026-10-19T08:46:05.740Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-26T14:34:25.811Z"},"containers":{"cna":{"title":"net/smc: fix use-after-free of the LLC qentry in smc_llc_srv_add_link()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix use-after-free of the LLC qentry in smc_llc_srv_add_link()\n\nsmc_llc_srv_add_link() keeps add_llc pointing into the queue entry:\n\n  add_llc = &qentry->msg.add_link;\t\t\tsmc_llc.c:1482\n  ...\n  smc_llc_save_add_link_info(link_new, add_llc);\tsmc_llc.c:1494\n  smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);\t\tsmc_llc.c:1495\n  ...\n  u8 *llc_msg = smc_link_shared_v2_rxbuf(link) ?\n\t(u8 *)lgr->wr_rx_buf_v2 : (u8 *)add_llc;\tsmc_llc.c:1504\n  smc_llc_save_add_link_rkeys(link, link_new, llc_msg);\tsmc_llc.c:1506\n\nsmc_llc_flow_qentry_del() kfree()s the entry, so on a link without a shared\nv2 receive buffer the pointer handed to smc_llc_save_add_link_rkeys() is\nalready freed. Before the Fixes: commit that branch always used\nlgr->wr_rx_buf_v2 and add_llc was not used after the free.\n\nReproduced on an unpatched tree over rxe, with KASAN, kasan_multi_shot\nand a link forced to max_recv_sge == 1: the entry is freed and read by\nthe same call, and the freeing frame is smc_llc_srv_add_link() itself.\n\n  [    2.523161] BUG: KASAN: slab-use-after-free in smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523499] Read of size 2 at addr ffff8880052194de by task kworker/0:1/11\n  [    2.523789]\n  [    2.523862] CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 7.2.0-rc5-p0-g2c9dd296545d #35 PREEMPT(lazy)\n  [    2.523865] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n  [    2.523866] Workqueue: smc_hs_wq smc_listen_work\n  [    2.523869] Call Trace:\n  [    2.523870]  <TASK>\n  [    2.523871]  dump_stack_lvl+0x53/0x70\n  [    2.523872]  print_report+0xd0/0x630\n  [    2.523874]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10\n  [    2.523876]  ? smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523878]  kasan_report+0xce/0x100\n  [    2.523879]  ? smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523881]  smc_llc_save_add_link_rkeys+0x333/0x350\n  [    2.523883]  ? smcr_buf_reg_lgr+0x2a4/0x660\n  [    2.523885]  smc_llc_srv_add_link+0xaa2/0x1e50\n  [    2.523888]  ? _printk+0xba/0xf0\n  [    2.523897]  ? __pfx_smc_llc_srv_add_link+0x10/0x10\n  [    2.523899]  ? down_write+0xb0/0x130\n  [    2.523903]  ? __pfx_down_write+0x10/0x10\n  [    2.523905]  smc_listen_work+0x489e/0x4d00\n  [    2.523907]  ? kmem_cache_free+0x1c6/0x3a0\n  [    2.523911]  ? __pfx_smc_listen_work+0x10/0x10\n  [    2.523913]  ? release_sock+0x148/0x1d0\n  [    2.523915]  ? smc_tcp_listen_work+0xb4f/0xfc0\n  [    2.523917]  ? _raw_spin_lock_irq+0x80/0xe0\n  [    2.523918]  ? __pfx__raw_spin_lock_irq+0x10/0x10\n  [    2.523920]  process_one_work+0x633/0x1030\n  [    2.523922]  ? assign_work+0x11d/0x370\n  [    2.523924]  worker_thread+0x45b/0xd10\n  [    2.523926]  ? __pfx_worker_thread+0x10/0x10\n  [    2.523928]  ? __pfx_worker_thread+0x10/0x10\n  [    2.523929]  kthread+0x2c6/0x3b0\n  [    2.523931]  ? recalc_sigpending+0x15c/0x1e0\n  [    2.523934]  ? __pfx_kthread+0x10/0x10\n  [    2.523935]  ret_from_fork+0x36e/0x5a0\n  [    2.523937]  ? __pfx_ret_from_fork+0x10/0x10\n  [    2.523938]  ? __switch_to+0x572/0xdd0\n  [    2.523943]  ? __pfx_kthread+0x10/0x10\n  [    2.523944]  ret_from_fork_asm+0x1a/0x30\n  [    2.523947]  </TASK>\n  [    2.523948]\n  [    2.531253] Allocated by task 48:\n  [    2.531399]  kasan_save_stack+0x33/0x60\n  [    2.531570]  kasan_save_track+0x14/0x30\n  [    2.531737]  __kasan_kmalloc+0x8f/0xa0\n  [    2.531905]  __kmalloc_cache_noprof+0x158/0x370\n  [    2.532100]  smc_llc_enqueue+0x72/0x560\n  [    2.532268]  smc_wr_rx_tasklet_fn+0x474/0xa80\n  [    2.532491]  tasklet_action_common+0x20f/0x8a0\n  [    2.532714]  handle_softirqs+0x18e/0x590\n  [    2.532886]  do_softirq+0x3b/0x60\n  [    2.533036]  __local_bh_enable_ip+0x61/0x70\n  [    2.533221]  __alloc_skb+0x732/0x890\n  [    2.533384]  rxe_init_packet+0x16b/0x4f0\n  [    2.533567]  prepare_ack_packet+0xb8/0x830\n  [    2.533760]  rxe_receiver+0x495/0x96e0\n  [    2.533933]  do_work+0x144/0x470\n  [    2\n---truncated---"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"27ef6a9981fe74191849966a6d5e0400a4008ab8","status":"affected","lessThan":"c52a998a223e7e84333306996edec096178d1e95","versionType":"git"},{"version":"27ef6a9981fe74191849966a6d5e0400a4008ab8","status":"affected","lessThan":"adef84cc85d449ac28d2b4b4c49cf19619c56e27","versionType":"git"},{"version":"27ef6a9981fe74191849966a6d5e0400a4008ab8","status":"affected","lessThan":"a42a459ef0e54cb0c4b3e43e21cb0e658e664f64","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_llc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_llc.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/c52a998a223e7e84333306996edec096178d1e95"},{"url":"https://git.kernel.org/stable/c/adef84cc85d449ac28d2b4b4c49cf19619c56e27"},{"url":"https://git.kernel.org/stable/c/a42a459ef0e54cb0c4b3e43e21cb0e658e664f64"}],"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 UAF is reached from smc_listen_work() (smc_listen_rdma_finish → smcr_serv_conf_first_link → smc_llc_srv_add_link) and from LLC ADD_LINK handling; CLC is plain TCP and SMC-Rv2/RoCEv2 LLC messages are IP-routable (UDP/4791), so a remote peer that can reach an AF_SMC listener drives the path.\nAC:L - The kfree of the LLC qentry and the later read in smc_llc_save_add_link_rkeys() run sequentially in the same call with no race; on an affected SMC-Rv2 link (max_recv_sge==1, the devices this bug exists for) a connecting peer that completes first-contact and replies to ADD_LINK triggers it reliably.\nPR:N - smc_listen_work() runs the CLC/LLC handshake after TCP accept and before accept() returns to userspace; SMC authenticates nothing, and smc_create()/smc_listen() enforce no capabilities, so an unauthenticated network peer needs only reachability to the listener.\nUI:N - The listen worker is queued automatically from smc_tcp_listen_work() for inbound connections; no local user action such as mounting a filesystem or opening a file is required.\nS:U - The use-after-free corrupts kernel heap state (the kmalloc-96 LLC qentry and link-group rtoken tables) within the same host kernel security authority; it is not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - The dangling add_llc pointer is a use-after-free read of a freed kmalloc-96 qentry (KASAN: slab-use-after-free in smc_llc_save_add_link_rkeys); per kernel CNA guidance a UAF of a generic slab object enables arbitrary kernel memory disclosure via heap reuse.\nI:H - smc_ib_ready_link()/smcr_buf_reg_lgr() allocate between the free and the UAF, so the object can be sprayed; smc_llc_save_add_link_rkeys() then writes those bytes into lgr->rtokens, a UAF-backed write primitive usable for arbitrary kernel modification or control-flow hijack.\nA:H - KASAN reports slab-use-after-free in smc_llc_save_add_link_rkeys() from smc_listen_work on smc_hs_wq; dereferencing freed heap from that kworker oopses or panics the kernel, and a remote peer can repeat the handshake at will."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:46:05.740Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}