{"api_version":"1","generated_at":"2026-10-25T07:17:58+00:00","cve":"CVE-2026-98642","urls":{"html":"https://cve.report/CVE-2026-98642","api":"https://cve.report/api/cve/CVE-2026-98642.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98642","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98642"},"summary":{"title":"bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk\n\nSyzkaller repeatedly triggered UAF splats related to nodes in\nwaiting_for_gp_ttrace within the bpf memalloc:\n\nBUG: KASAN: slab-use-after-free in llist_del_first+0x85/0x110 lib/llist.c:61\nRead of size 8 at addr ffff8881572cd080 by task syz.4.470/5112\n ...\n llist_del_first+0x85/0x110 lib/llist.c:61\n alloc_bulk+0x193/0x460 kernel/bpf/memalloc.c:229\n bpf_mem_refill+0x386/0x560 kernel/bpf/memalloc.c:436\n\nFreed by task 14:\n ...\n __free_rcu kernel/bpf/memalloc.c:281 [inline]\n __free_rcu_tasks_trace+0x48/0xd0 kernel/bpf/memalloc.c:291\n rcu_tasks_invoke_cbs+0x1ec/0x3e0 kernel/rcu/tasks.h:571\n rcu_tasks_one_gp+0x13d/0x220 kernel/rcu/tasks.h:621\n rcu_tasks_kthread+0xf3/0x120 kernel/rcu/tasks.h:651\n\nThe reason is that the UAF occurs after the RCU Tasks Trace GP expires:\nwhen the __free_rcu() callback runs, there is no synchronization\nprotecting llist_del_all() against concurrent alloc_bulk() operating on\nwaiting_for_gp_ttrace, leading to the race condition below:\n\nCPU0                                           CPU1\n                                               __free_rcu (RCU Tasks Trace callback)\nalloc_bulk\n  llist_del_first(&c->waiting_for_gp_ttrace)\n    entry = smp_load_acquire(&head->first);\n    do {\n      if (entry == NULL)\n        return NULL;\n                                               free_all(llist_del_all(&c->waiting_for_gp_ttrace))\n                                                 llist_for_each_safe(pos, t, llnode)\n                                                   free_one(pos);\n      next = READ_ONCE(entry->next); <-- trigger UAF\n    } while (!try_cmpxchg(&head->first, &entry, next));\n\nIn addition, there is also a theoretical race condition on the\nfree_by_rcu_ttrace list. This race requires two preconditions: an\nin-flight Tasks Trace GP keeping c->call_rcu_ttrace_in_progress == 1,\nand concurrent cross-CPU frees repopulating c->free_by_rcu_ttrace with\nnew nodes. Under these conditions, the following scenario triggers UAF:\n\n// CPU0\n// irq work is still busy (on PREEMPT_RT)\nalloc_bulk()\n  llist_del_first(&c->free_by_rcu_ttrace)\n    entry = smp_load_acquire(&head->first);\n    do {\n      if (entry == NULL)\n        return NULL;\n\n        // CPU1\n        bpf_mem_alloc_destroy()\n          WRITE_ONCE(c->draining, true)\n          // wait for CPU0\n          irq_work_sync()\n\n                // CPU2\n                do_call_rcu_ttrace(tgt(CPU0))\n                  if (c->draining) {\n                    llist_del_all(&c->free_by_rcu_ttrace)\n                    free_all()\n                  }\n\n// CPU0 continue\n      next = READ_ONCE(entry->next); <-- trigger UAF\n    while (!try_cmpxchg(&head->first, &entry, next));\n\nFix this by introducing a raw spinlock to synchronize the concurrent\nconsumption on waiting_for_gp_ttrace and free_by_rcu_ttrace.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-18 16:17:17","updated_at":"2026-10-19 10:19:28"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/1c21452d02eec2f008e2c5535820f85adbd7587a","name":"https://git.kernel.org/stable/c/1c21452d02eec2f008e2c5535820f85adbd7587a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a0e150a118025a05c8662c536ba2a865da86419c","name":"https://git.kernel.org/stable/c/a0e150a118025a05c8662c536ba2a865da86419c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f101602415fb39a58941bec444df65634d5a6844","name":"https://git.kernel.org/stable/c/f101602415fb39a58941bec444df65634d5a6844","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1d6581b544a88cf4348c2fb60dcb50ad63f012da","name":"https://git.kernel.org/stable/c/1d6581b544a88cf4348c2fb60dcb50ad63f012da","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98642","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98642","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 04fabf00b4d3aff5d010ecb617001814e409e24a a0e150a118025a05c8662c536ba2a865da86419c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 04fabf00b4d3aff5d010ecb617001814e409e24a 1d6581b544a88cf4348c2fb60dcb50ad63f012da git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 04fabf00b4d3aff5d010ecb617001814e409e24a f101602415fb39a58941bec444df65634d5a6844 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 04fabf00b4d3aff5d010ecb617001814e409e24a 1c21452d02eec2f008e2c5535820f85adbd7587a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.6","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.112 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.55 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.9 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["kernel/bpf/memalloc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"a0e150a118025a05c8662c536ba2a865da86419c","status":"affected","version":"04fabf00b4d3aff5d010ecb617001814e409e24a","versionType":"git"},{"lessThan":"1d6581b544a88cf4348c2fb60dcb50ad63f012da","status":"affected","version":"04fabf00b4d3aff5d010ecb617001814e409e24a","versionType":"git"},{"lessThan":"f101602415fb39a58941bec444df65634d5a6844","status":"affected","version":"04fabf00b4d3aff5d010ecb617001814e409e24a","versionType":"git"},{"lessThan":"1c21452d02eec2f008e2c5535820f85adbd7587a","status":"affected","version":"04fabf00b4d3aff5d010ecb617001814e409e24a","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["kernel/bpf/memalloc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.6"},{"lessThan":"6.6","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.112","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.55","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.112","versionStartIncluding":"6.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.55","versionStartIncluding":"6.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.9","versionStartIncluding":"6.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"6.6","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk\n\nSyzkaller repeatedly triggered UAF splats related to nodes in\nwaiting_for_gp_ttrace within the bpf memalloc:\n\nBUG: KASAN: slab-use-after-free in llist_del_first+0x85/0x110 lib/llist.c:61\nRead of size 8 at addr ffff8881572cd080 by task syz.4.470/5112\n ...\n llist_del_first+0x85/0x110 lib/llist.c:61\n alloc_bulk+0x193/0x460 kernel/bpf/memalloc.c:229\n bpf_mem_refill+0x386/0x560 kernel/bpf/memalloc.c:436\n\nFreed by task 14:\n ...\n __free_rcu kernel/bpf/memalloc.c:281 [inline]\n __free_rcu_tasks_trace+0x48/0xd0 kernel/bpf/memalloc.c:291\n rcu_tasks_invoke_cbs+0x1ec/0x3e0 kernel/rcu/tasks.h:571\n rcu_tasks_one_gp+0x13d/0x220 kernel/rcu/tasks.h:621\n rcu_tasks_kthread+0xf3/0x120 kernel/rcu/tasks.h:651\n\nThe reason is that the UAF occurs after the RCU Tasks Trace GP expires:\nwhen the __free_rcu() callback runs, there is no synchronization\nprotecting llist_del_all() against concurrent alloc_bulk() operating on\nwaiting_for_gp_ttrace, leading to the race condition below:\n\nCPU0                                           CPU1\n                                               __free_rcu (RCU Tasks Trace callback)\nalloc_bulk\n  llist_del_first(&c->waiting_for_gp_ttrace)\n    entry = smp_load_acquire(&head->first);\n    do {\n      if (entry == NULL)\n        return NULL;\n                                               free_all(llist_del_all(&c->waiting_for_gp_ttrace))\n                                                 llist_for_each_safe(pos, t, llnode)\n                                                   free_one(pos);\n      next = READ_ONCE(entry->next); <-- trigger UAF\n    } while (!try_cmpxchg(&head->first, &entry, next));\n\nIn addition, there is also a theoretical race condition on the\nfree_by_rcu_ttrace list. This race requires two preconditions: an\nin-flight Tasks Trace GP keeping c->call_rcu_ttrace_in_progress == 1,\nand concurrent cross-CPU frees repopulating c->free_by_rcu_ttrace with\nnew nodes. Under these conditions, the following scenario triggers UAF:\n\n// CPU0\n// irq work is still busy (on PREEMPT_RT)\nalloc_bulk()\n  llist_del_first(&c->free_by_rcu_ttrace)\n    entry = smp_load_acquire(&head->first);\n    do {\n      if (entry == NULL)\n        return NULL;\n\n        // CPU1\n        bpf_mem_alloc_destroy()\n          WRITE_ONCE(c->draining, true)\n          // wait for CPU0\n          irq_work_sync()\n\n                // CPU2\n                do_call_rcu_ttrace(tgt(CPU0))\n                  if (c->draining) {\n                    llist_del_all(&c->free_by_rcu_ttrace)\n                    free_all()\n                  }\n\n// CPU0 continue\n      next = READ_ONCE(entry->next); <-- trigger UAF\n    while (!try_cmpxchg(&head->first, &entry, next));\n\nFix this by introducing a raw spinlock to synchronize the concurrent\nconsumption on waiting_for_gp_ttrace and free_by_rcu_ttrace."}],"providerMetadata":{"dateUpdated":"2026-10-19T09:23:11.995Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/a0e150a118025a05c8662c536ba2a865da86419c"},{"url":"https://git.kernel.org/stable/c/1d6581b544a88cf4348c2fb60dcb50ad63f012da"},{"url":"https://git.kernel.org/stable/c/f101602415fb39a58941bec444df65634d5a6844"},{"url":"https://git.kernel.org/stable/c/1c21452d02eec2f008e2c5535820f85adbd7587a"}],"title":"bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98642","datePublished":"2026-10-18T15:20:13.740Z","dateReserved":"2026-09-25T10:25:14.361Z","dateUpdated":"2026-10-19T09:23:11.995Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 16:17:17","lastModifiedDate":"2026-10-19 10:19:28","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98642","Ordinal":"1","Title":"bpf: Fix UAF due to concurrent consumption of ttrace lists in al","CVE":"CVE-2026-98642","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98642","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk\n\nSyzkaller repeatedly triggered UAF splats related to nodes in\nwaiting_for_gp_ttrace within the bpf memalloc:\n\nBUG: KASAN: slab-use-after-free in llist_del_first+0x85/0x110 lib/llist.c:61\nRead of size 8 at addr ffff8881572cd080 by task syz.4.470/5112\n ...\n llist_del_first+0x85/0x110 lib/llist.c:61\n alloc_bulk+0x193/0x460 kernel/bpf/memalloc.c:229\n bpf_mem_refill+0x386/0x560 kernel/bpf/memalloc.c:436\n\nFreed by task 14:\n ...\n __free_rcu kernel/bpf/memalloc.c:281 [inline]\n __free_rcu_tasks_trace+0x48/0xd0 kernel/bpf/memalloc.c:291\n rcu_tasks_invoke_cbs+0x1ec/0x3e0 kernel/rcu/tasks.h:571\n rcu_tasks_one_gp+0x13d/0x220 kernel/rcu/tasks.h:621\n rcu_tasks_kthread+0xf3/0x120 kernel/rcu/tasks.h:651\n\nThe reason is that the UAF occurs after the RCU Tasks Trace GP expires:\nwhen the __free_rcu() callback runs, there is no synchronization\nprotecting llist_del_all() against concurrent alloc_bulk() operating on\nwaiting_for_gp_ttrace, leading to the race condition below:\n\nCPU0                                           CPU1\n                                               __free_rcu (RCU Tasks Trace callback)\nalloc_bulk\n  llist_del_first(&c->waiting_for_gp_ttrace)\n    entry = smp_load_acquire(&head->first);\n    do {\n      if (entry == NULL)\n        return NULL;\n                                               free_all(llist_del_all(&c->waiting_for_gp_ttrace))\n                                                 llist_for_each_safe(pos, t, llnode)\n                                                   free_one(pos);\n      next = READ_ONCE(entry->next); <-- trigger UAF\n    } while (!try_cmpxchg(&head->first, &entry, next));\n\nIn addition, there is also a theoretical race condition on the\nfree_by_rcu_ttrace list. This race requires two preconditions: an\nin-flight Tasks Trace GP keeping c->call_rcu_ttrace_in_progress == 1,\nand concurrent cross-CPU frees repopulating c->free_by_rcu_ttrace with\nnew nodes. Under these conditions, the following scenario triggers UAF:\n\n// CPU0\n// irq work is still busy (on PREEMPT_RT)\nalloc_bulk()\n  llist_del_first(&c->free_by_rcu_ttrace)\n    entry = smp_load_acquire(&head->first);\n    do {\n      if (entry == NULL)\n        return NULL;\n\n        // CPU1\n        bpf_mem_alloc_destroy()\n          WRITE_ONCE(c->draining, true)\n          // wait for CPU0\n          irq_work_sync()\n\n                // CPU2\n                do_call_rcu_ttrace(tgt(CPU0))\n                  if (c->draining) {\n                    llist_del_all(&c->free_by_rcu_ttrace)\n                    free_all()\n                  }\n\n// CPU0 continue\n      next = READ_ONCE(entry->next); <-- trigger UAF\n    while (!try_cmpxchg(&head->first, &entry, next));\n\nFix this by introducing a raw spinlock to synchronize the concurrent\nconsumption on waiting_for_gp_ttrace and free_by_rcu_ttrace.","Type":"Description","Title":"bpf: Fix UAF due to concurrent consumption of ttrace lists in al"}]}}}