bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO
states.c:__clean_func_state() can downgrade scalar zero spill to
STACK_ZERO in the following case:
*(u64 *)(r10 - 8) = 0;
... checkpoint ...
r1 = *(u32 *)(r10 - 4);
... no reads from r10-8 ...
Here 4 bytes at r10-8 are dead and verifier changes scalar spill to a
combination: 0000pppp (p stands for poison). Such a change breaks
precision propagation chains. All places that produce STACK_ZERO
should call bpf_mark_chain_precision() for the zero source.
This patch fixes the bug in a simplest way possible:
avoids converting stack spills of zero to STACK_ZERO.
Two smarter approaches are possible:
- do bpf_mark_chain_precision() from __clean_func_state()
- check slot liveness information in check_stack_write_fixed_off()
I investigated both and the changes required are a bit tricky,
hence go with a simple fix for the time being.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data.
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| Vendor | Product | Confidence | Versions | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux Kernel | 99% |
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| Linux | Linux Kernel | 99% |
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No vendor fix or workaround currently provided.
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Tracking
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Fri, 25 Sep 2026 13:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-284 |
Fri, 25 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO states.c:__clean_func_state() can downgrade scalar zero spill to STACK_ZERO in the following case: *(u64 *)(r10 - 8) = 0; ... checkpoint ... r1 = *(u32 *)(r10 - 4); ... no reads from r10-8 ... Here 4 bytes at r10-8 are dead and verifier changes scalar spill to a combination: 0000pppp (p stands for poison). Such a change breaks precision propagation chains. All places that produce STACK_ZERO should call bpf_mark_chain_precision() for the zero source. This patch fixes the bug in a simplest way possible: avoids converting stack spills of zero to STACK_ZERO. Two smarter approaches are possible: - do bpf_mark_chain_precision() from __clean_func_state() - check slot liveness information in check_stack_write_fixed_off() I investigated both and the changes required are a bit tricky, hence go with a simple fix for the time being. | |
| Title | bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:36:11.662Z
Reserved: 2026-09-25T10:25:14.318Z
Link: CVE-2026-98132
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:44.603
Modified: 2026-09-25T11:17:44.603
Link: CVE-2026-98132
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-25T17:45:17Z