bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98132
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 11:17:44 UTC
Updated2026-09-25 11:17:44 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected be23266b4a08540aa43d8503a2ea10247c8daebe 436fa689630b741a77ef8c4a6f426479affd5bac git Not specified
CNA Linux Linux affected be23266b4a08540aa43d8503a2ea10247c8daebe 2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e git Not specified
CNA Linux Linux affected 7.1 Not specified
CNA Linux Linux unaffected 7.1 semver Not specified
CNA Linux Linux unaffected 7.2.7 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/436fa689630b741a77ef8c4a6f426479affd5bac 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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