bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk Syzkaller repeatedly triggered UAF splats related to nodes in waiting_for_gp_ttrace within the bpf memalloc: BUG: KASAN: slab-use-after-free in llist_del_first+0x85/0x110 lib/llist.c:61 Read of size 8 at addr ffff8881572cd080 by task syz.4.470/5112 ... llist_del_first+0x85/0x110 lib/llist.c:61 alloc_bulk+0x193/0x460 kernel/bpf/memalloc.c:229 bpf_mem_refill+0x386/0x560 kernel/bpf/memalloc.c:436 Freed by task 14: ... __free_rcu kernel/bpf/memalloc.c:281 [inline] __free_rcu_tasks_trace+0x48/0xd0 kernel/bpf/memalloc.c:291 rcu_tasks_invoke_cbs+0x1ec/0x3e0 kernel/rcu/tasks.h:571 rcu_tasks_one_gp+0x13d/0x220 kernel/rcu/tasks.h:621 rcu_tasks_kthread+0xf3/0x120 kernel/rcu/tasks.h:651 The reason is that the UAF occurs after the RCU Tasks Trace GP expires: when the __free_rcu() callback runs, there is no synchronization protecting llist_del_all() against concurrent alloc_bulk() operating on waiting_for_gp_ttrace, leading to the race condition below: CPU0 CPU1 __free_rcu (RCU Tasks Trace callback) alloc_bulk llist_del_first(&c->waiting_for_gp_ttrace) entry = smp_load_acquire(&head->first); do { if (entry == NULL) return NULL; free_all(llist_del_all(&c->waiting_for_gp_ttrace)) llist_for_each_safe(pos, t, llnode) free_one(pos); next = READ_ONCE(entry->next); <-- trigger UAF } while (!try_cmpxchg(&head->first, &entry, next)); In addition, there is also
CVE-2026-98642
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-98642
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "04fabf00b4d3aff5d010ecb617001814e409e24a",
"lessThan": "a0e150a118025a05c8662c536ba2a865da86419c",
"versionType": "git"
},
{
"status": "affected",
"version": "04fabf00b4d3aff5d010ecb617001814e409e24a",
"lessThan": "1d6581b544a88cf4348c2fb60dcb50ad63f012da",
"versionType": "git"
},
{
"status": "affected",
"version": "04fabf00b4d3aff5d010ecb617001814e409e24a",
"lessThan": "f101602415fb39a58941bec444df65634d5a6844",
"versionType": "git"
},
{
"status": "affected",
"version": "04fabf00b4d3aff5d010ecb617001814e409e24a",
"lessThan": "1c21452d02eec2f008e2c5535820f85adbd7587a",
"versionType": "git"
}
],
"programFiles": [
"kernel/bpf/memalloc.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.6"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.6",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.55",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.9",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/memalloc.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98642
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #38662 · Revision 1
- Added to Heist Feed
- Publisher date