bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos

Vulnerability Description

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.

References

• https://git.kernel.org/stable/c/dc7ce14f00bcd50641f2110b7a32aa6552e0780f
• https://git.kernel.org/stable/c/2288b54b96dcb55bedebcef3572bb8821fc5e708
• https://git.kernel.org/stable/c/584cd3ff792e1edbea20b2a7df55897159b0be3e
• https://git.kernel.org/stable/c/e7e9c5b2dda29067332df2a85b0141a92b41f218
• https://git.kernel.org/stable/c/3d2786d65aaa954ebd3fcc033ada433e10da21c4