CVE-2024-49850 — bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos

Affected: Linux

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

bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos

In case of malformed relocation record of kind BPF_CORE_TYPE_ID_LOCAL referencing a non-existing BTF type, function bpf_core_calc_relo_insn would cause a null pointer deference.

Fix this by adding a proper check upper in call stack, as malformed relocation records could be passed from user space.

Simplest reproducer is a program:

r0 = 0 exit

With a single relocation record:

.insn_off = 0, /* patch first instruction */ .type_id = 100500, /* this type id does not exist */ .access_str_off = 6, /* offset of string "0" */ .kind = BPF_CORE_TYPE_ID_LOCAL,

See the link for original reproducer or next commit for a test case.

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CVE-2024-49850 — bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos