CVE-2026-72426 — bpf: Preserve pointer spill metadata during half-slot cleanup

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

bpf: Preserve pointer spill metadata during half-slot cleanup

__clean_func_state() cleans dead stack slots in 4-byte halves. When the high half of a STACK_SPILL slot is dead and the low half remains live, cleanup converts the live low half to STACK_MISC or STACK_ZERO and clears the saved spilled_ptr metadata.

That conversion is safe only for scalar spills. For a pointer spill, this metadata clear lets a later 32-bit fill from the still-live half avoid the normal non-scalar register-fill check and be treated as an ordinary scalar stack read.

Leave non-scalar spill slots intact in this half-live shape. This is conservative for pruning and preserves the existing check_stack_read_fixed_off() rejection path for partial fills from pointer spills.

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CVE-2026-72426 — bpf: Preserve pointer spill metadata during half-slot cleanup