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Kernel: Plumb the elf header of the main program down to Process::load

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This will enable us to take the desired load address of non-position
independent programs into account when randomizing the load address
of the dynamic loader.
This commit is contained in:
Itamar 2021-01-10 21:07:08 +02:00 • committed by Andreas Kling
parent f369229770
commit 40a8159c62
2 changed files with 25 additions and 24 deletions
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42
Kernel/Syscalls/execve.cpp
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@ -276,7 +276,7 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
};
}
KResultOr<Process::LoadResult> Process::load(NonnullRefPtr<FileDescription> main_program_description, RefPtr<FileDescription> interpreter_description, bool is_dynamic)
KResultOr<Process::LoadResult> Process::load(NonnullRefPtr<FileDescription> main_program_description, RefPtr<FileDescription> interpreter_description, const Elf32_Ehdr& main_program_header)
{
RefPtr<PageDirectory> old_page_directory;
NonnullOwnPtrVector<Region> old_regions;
@ -308,7 +308,7 @@ KResultOr<Process::LoadResult> Process::load(NonnullRefPtr<FileDescription> main
m_regions = move(old_regions);
});
if (!is_dynamic) {
if (interpreter_description.is_null()) {
auto result = load_elf_object(main_program_description, FlatPtr { 0 }, ShouldAllocateTls::Yes);
if (result.is_error())
return result.error();
@ -394,7 +394,7 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
}
}
auto load_result_or_error = load(main_program_description, interpreter_description, is_dynamic);
auto load_result_or_error = load(main_program_description, interpreter_description, main_program_header);
if (load_result_or_error.is_error()) {
dbgln("do_exec({}): Failed to load main program or interpreter", path);
return load_result_or_error.error();
@ -583,20 +583,12 @@ static KResultOr<Vector<String>> find_shebang_interpreter_for_executable(const c
return KResult(-ENOEXEC);
}
KResultOr<RefPtr<FileDescription>> Process::find_elf_interpreter_for_executable(const String& path, char (&first_page)[PAGE_SIZE], int nread, size_t file_size)
KResultOr<RefPtr<FileDescription>> Process::find_elf_interpreter_for_executable(const String& path, const Elf32_Ehdr& main_program_header, int nread, size_t file_size)
{
if (nread < (int)sizeof(Elf32_Ehdr))
return KResult(-ENOEXEC);
auto elf_header = (Elf32_Ehdr*)first_page;
if (!ELF::validate_elf_header(*elf_header, file_size)) {
dbgln("exec({}): File has invalid ELF header", path);
return KResult(-ENOEXEC);
}
// Not using KResultOr here because we'll want to do the same thing in userspace in the RTLD
String interpreter_path;
if (!ELF::validate_program_headers(*elf_header, file_size, (u8*)first_page, nread, &interpreter_path)) {
if (!ELF::validate_program_headers(main_program_header, file_size, (const u8*)&main_program_header, nread, &interpreter_path)) {
dbgln("exec({}): File has invalid ELF Program headers", path);
return KResult(-ENOEXEC);
}
@ -621,7 +613,7 @@ KResultOr<RefPtr<FileDescription>> Process::find_elf_interpreter_for_executable(
if (interp_metadata.size < (int)sizeof(Elf32_Ehdr))
return KResult(-ENOEXEC);
memset(first_page, 0, sizeof(first_page));
char first_page[PAGE_SIZE] = {};
auto first_page_buffer = UserOrKernelBuffer::for_kernel_buffer((u8*)&first_page);
auto nread_or_error = interpreter_description->read(first_page_buffer, sizeof(first_page));
if (nread_or_error.is_error())
@ -631,7 +623,7 @@ KResultOr<RefPtr<FileDescription>> Process::find_elf_interpreter_for_executable(
if (nread < (int)sizeof(Elf32_Ehdr))
return KResult(-ENOEXEC);
elf_header = (Elf32_Ehdr*)first_page;
auto elf_header = (Elf32_Ehdr*)first_page;
if (!ELF::validate_elf_header(*elf_header, interp_metadata.size)) {
dbgln("exec({}): Interpreter ({}) has invalid ELF header", path, interpreter_description->absolute_path());
return KResult(-ENOEXEC);
@ -652,11 +644,11 @@ KResultOr<RefPtr<FileDescription>> Process::find_elf_interpreter_for_executable(
return interpreter_description;
}
if (elf_header->e_type == ET_REL) {
if (main_program_header.e_type == ET_REL) {
// We can't exec an ET_REL, that's just an object file from the compiler
return KResult(-ENOEXEC);
}
if (elf_header->e_type == ET_DYN) {
if (main_program_header.e_type == ET_DYN) {
// If it's ET_DYN with no PT_INTERP, then it's a dynamic executable responsible
// for its own relocation (i.e. it's /usr/lib/Loader.so)
if (path != "/usr/lib/Loader.so")
@ -715,15 +707,23 @@ int Process::exec(String path, Vector<String> arguments, Vector<String> environm
}
// #2) ELF32 for i386
auto elf_result = find_elf_interpreter_for_executable(path, first_page, nread_or_error.value(), metadata.size);
if (nread_or_error.value() < (int)sizeof(Elf32_Ehdr))
return KResult(-ENOEXEC);
auto main_program_header = (Elf32_Ehdr*)first_page;
if (!ELF::validate_elf_header(*main_program_header, metadata.size)) {
dbgln("exec({}): File has invalid ELF header", path);
return KResult(-ENOEXEC);
}
auto elf_result = find_elf_interpreter_for_executable(path, *main_program_header, nread_or_error.value(), metadata.size);
// Assume a static ELF executable by default
RefPtr<FileDescription> interpreter_description;
bool is_dynamic = false;
// We're getting either an interpreter, an error, or KSuccess (i.e. no interpreter but file checks out)
if (!elf_result.is_error()) {
// It's a dynamic ELF executable, with or without an interpreter. Do not allocate TLS
interpreter_description = elf_result.value();
is_dynamic = true;
} else if (elf_result.error().is_error())
return elf_result.error();
@ -731,7 +731,7 @@ int Process::exec(String path, Vector<String> arguments, Vector<String> environm
// are cleaned up by the time we yield-teleport below.
Thread* new_main_thread = nullptr;
u32 prev_flags = 0;
int rc = do_exec(move(description), move(arguments), move(environment), move(interpreter_description), new_main_thread, prev_flags, is_dynamic);
int rc = do_exec(move(description), move(arguments), move(environment), move(interpreter_description), new_main_thread, prev_flags, *main_program_header);
m_exec_tid = 0;