Bug 2536167 (CVE-2026-90317)

Summary: CVE-2026-90317 kernel: bpf: Invalidate RCU pointers after final spin unlock
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Berkeley Packet Filter (BPF) subsystem. In sleepable BPF programs, a use-after-free vulnerability can occur due to improper handling of RCU (Read-Copy-Update) protected pointers after a spin unlock operation. A local attacker with limited capabilities could exploit this flaw to trigger a `task_struct` use-after-free, potentially leading to a denial of service or privilege escalation.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-17 16:41:08 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Invalidate RCU pointers after final spin unlock

In a sleepable BPF program, a spin lock can provide the only RCU protection
for a kptr. The final bpf_spin_unlock() ends that protection, but the
verifier leaves the pointer valid. Another CPU can then free the object
before the pointer is used. A capability-limited runtime PoC triggered a
task_struct use-after-free in __bpf_get_task_stack().

Record whether the program is in an RCU-protected context before releasing
the lock. Invalidate RCU-protected pointers only when the unlock leaves the
final such context. This preserves valid pointers in non-sleepable programs
and inside an explicit RCU read-side section.
Comment 1 gkamathe 2026-09-23 07:36:19 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90317.mbox