Bug 2555031 (CVE-2026-98628)

Summary: CVE-2026-98628 kernel: bpf: Make post-verification instruction rewrites killable
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
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 BPF (Berkeley Packet Filter) subsystem. A privileged local user can cause a Denial of Service (DoS) by loading a specially crafted BPF program containing numerous redundant instructions that trigger intensive post-verification cleanup. Because these rewrite operations do not check for termination signals or yield processor time, the task enters an uninterruptible state that ignores termination requests until the work completes, leading to prolonged resource consumption.
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Description OSIDB Bzimport 2026-10-18 15:40:22 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Make post-verification instruction rewrites killable

After do_check() returns, the verifier runs several instruction rewrite
passes. Some of them patch or remove one instruction at a time. Each
operation moves the remaining instruction and auxiliary-data arrays and
adjusts all branch offsets, making the overall work quadratic in the
program length.

A privileged loader can submit 131072 unconditional jumps by zero followed
by a valid return. Verification finishes quickly, but bpf_opt_remove_nops()
then spends a long time removing each jump separately. Since this
post-verification work neither checks for signals nor reschedules, a pending
SIGKILL cannot terminate the task until the rewrite finishes.

Make bpf_patch_insn_data() and verifier_remove_insns() common cancellation
and rescheduling points. These helpers run from BPF_PROG_LOAD process
context, and bpf_patch_insn_data() can already sleep while reallocating
auxiliary data.

Report interrupted constant blinding as -EINTR and propagate it through
both JIT paths, including kernels that permit interpreter fallback.
Other blinding failures retain the existing fallback behavior.

This does not reduce the quadratic cost of the rewrite passes, but it makes
the work preemptible and allows a killed loader to be torn down promptly.