In the Linux kernel, the following vulnerability has been resolved: bpf: Fix REG INVARIANTS VIOLATION on speculative pointer arithmetic Take the following unprivileged program as an example: r0 = bpf_map_lookup_elem(...) /* PTR_TO_MAP_VALUE, offset 0 */ ... 14: r0 += r1 /* r1 is a bounded scalar */ 15: r9 = r0 Loading it triggers a verifier warning from reg_bounds_sanity_check(): verifier bug: REG INVARIANTS VIOLATION (alu): const subreg tnum out of sync with range bounds r64={.base=0x0, .size=0x0} r32={.base=0x0, .size=0xffffffff} var_off=(0x0, 0x0) What happens: 1. Processing insn 14 (r0 += r1) in adjust_ptr_min_max_vals(), the new offset is computed into dst_reg's var_off and 32/64-bit ranges. 2. Because pointer registers do not track 32-bit subregister bounds, __mark_reg32_unbounded()…
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