dthaler
commented
3 years ago The ebpf-verifier fix in 239 was not sufficient. The following warning remains:
D:\a\ebpf-for-windows\ebpf-for-windows\external\ebpf-verifier\src\asm_files.cpp(131): error C6011: Dereferencing NULL pointer 'maps_section'.
Offhand it looks like a false positive. Code:
if (reloc.get_entries_num() && !maps_section) {
throw std::runtime_error(string("Can't find any maps sections in file ") + path);
}
for (ELFIO::Elf_Xword i = 0; i < reloc.get_entries_num(); i++) {
if (reloc.get_entry(i, offset, symbol, type, addend)) {
ebpf_inst& inst = prog.prog[offset / sizeof(ebpf_inst)];
string symbol_name;
ELFIO::Elf64_Addr symbol_value{};
unsigned char symbol_bind{};
unsigned char symbol_type{};
ELFIO::Elf_Half symbol_section_index{};
unsigned char symbol_other{};
ELFIO::Elf_Xword symbol_size{};
symbols.get_symbol(symbol, symbol_name, symbol_value, symbol_size, symbol_bind, symbol_type,
symbol_section_index, symbol_other);
// Only perform relocation for symbols located in the maps section.
if (symbol_section_index != maps_section->get_index()) {The first check will throw if maps_section is null and there are reloc entries.
And the warning is generated inside the loop that is only traversed if there are reloc entries.
I suspect the analyzer doesn't know whether reloc.get_entries_num() can change in between the two checks. Maybe saving it in a local variable will make the analyzer happy.
Alan-Jowett
Revert C6011 override in external\Analyze.external.ruleset once upstream issue is fixed.
Due to https://github.com/vbpf/ebpf-verifier/issues/239 there is an override that make C6011 a warning in the external submodules. Once this is resolved, remove this overide.