{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98642", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.361Z", "datePublished": "2026-10-18T15:20:13.740Z", "dateUpdated": "2026-10-19T09:23:11.995Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:23:11.995Z" }, "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." } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/memalloc.c" ], "versions": [ { "version": "04fabf00b4d3aff5d010ecb617001814e409e24a", "lessThan": "a0e150a118025a05c8662c536ba2a865da86419c", "status": "affected", "versionType": "git" }, { "version": "04fabf00b4d3aff5d010ecb617001814e409e24a", "lessThan": "1d6581b544a88cf4348c2fb60dcb50ad63f012da", "status": "affected", "versionType": "git" }, { "version": "04fabf00b4d3aff5d010ecb617001814e409e24a", "lessThan": "f101602415fb39a58941bec444df65634d5a6844", "status": "affected", "versionType": "git" }, { "version": "04fabf00b4d3aff5d010ecb617001814e409e24a", "lessThan": "1c21452d02eec2f008e2c5535820f85adbd7587a", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/memalloc.c" ], "versions": [ { "version": "6.6", "status": "affected" }, { "version": "0", "lessThan": "6.6", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.112", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.55", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.9", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "6.6", "versionEndExcluding": "6.12.112" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.18.55" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.2.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.3" } ] } ] } ], "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" } } } }