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Kernel+LibELF: Abort ELF executable load sooner when something fails

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Make it possible to bail out of ELF::Image::for_each_program_header()
and then do exactly that if something goes wrong during executable
loading in the kernel.

Also make the errors we return slightly more nuanced than just ENOEXEC.
This commit is contained in:
Andreas Kling 2020-12-25 14:42:42 +01:00
parent 791b32e3c6
commit 6c9a6bea1e
5 changed files with 52 additions and 39 deletions
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4
DevTools/UserspaceEmulator/Emulator.cpp
View file

@ -208,8 +208,10 @@ bool Emulator::load_elf()
m_loader_text_size = region->size();
}
mmu().add_region(move(region));
return;
return IterationDecision::Continue;
}
return IterationDecision::Continue;
});
auto entry_point = interpreter_image.entry().offset(interpreter_load_offset).get();

49
Kernel/Syscalls/execve.cpp
View file

@ -91,7 +91,7 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
String elf_name = object_description.absolute_path();
ASSERT(!Processor::current().in_critical());
bool failed = false;
KResult ph_load_result = KSuccess;
elf_image.for_each_program_header([&](const ELF::Image::ProgramHeader& program_header) {
if (program_header.type() == PT_TLS) {
ASSERT(should_allocate_tls == ShouldAllocateTls::Yes);
@ -99,34 +99,36 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
if (!elf_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbgln("Shenanigans! ELF PT_TLS header sneaks outside of executable.");
failed = true;
return;
ph_load_result = KResult(-ENOEXEC);
return IterationDecision::Break;
}
master_tls_region = allocate_region({}, program_header.size_in_memory(), String::formatted("{} (master-tls)", elf_name), PROT_READ | PROT_WRITE);
if (!master_tls_region) {
failed = true;
return;
ph_load_result = KResult(-ENOMEM);
return IterationDecision::Break;
}
master_tls_size = program_header.size_in_memory();
master_tls_alignment = program_header.alignment();
if (!copy_to_user(master_tls_region->vaddr().as_ptr(), program_header.raw_data(), program_header.size_in_image())) {
failed = false;
return;
ph_load_result = KResult(-EFAULT);
return IterationDecision::Break;
}
return;
return IterationDecision::Continue;
}
if (program_header.type() != PT_LOAD)
return;
return IterationDecision::Continue;
if (program_header.is_writable()) {
// Writable section: create a copy in memory.
ASSERT(program_header.size_in_memory());
ASSERT(program_header.alignment() == PAGE_SIZE);
if (!elf_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbgln("Shenanigans! Writable ELF PT_LOAD header sneaks outside of executable.");
failed = true;
return;
ph_load_result = KResult(-ENOEXEC);
return IterationDecision::Break;
}
int prot = 0;
@ -137,8 +139,8 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
auto region_name = String::formatted("{} (data-{}{})", elf_name, program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : "");
auto* region = allocate_region(program_header.vaddr().offset(load_offset), program_header.size_in_memory(), move(region_name), prot);
if (!region) {
failed = true;
return;
ph_load_result = KResult(-ENOMEM);
return IterationDecision::Break;
}
// It's not always the case with PIE executables (and very well shouldn't be) that the
@ -151,10 +153,13 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
auto page_offset = program_header.vaddr();
page_offset.mask(~PAGE_MASK);
if (!copy_to_user((u8*)region->vaddr().as_ptr() + page_offset.get(), program_header.raw_data(), program_header.size_in_image())) {
failed = false;
return;
ph_load_result = KResult(-EFAULT);
return IterationDecision::Break;
}
} else {
return IterationDecision::Continue;
}
// Non-writable section: map the executable itself in memory.
ASSERT(program_header.size_in_memory());
ASSERT(program_header.alignment() == PAGE_SIZE);
int prot = 0;
@ -166,18 +171,18 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
prot |= PROT_EXEC;
auto* region = allocate_region_with_vmobject(program_header.vaddr().offset(load_offset), program_header.size_in_memory(), *vmobject, program_header.offset(), elf_name, prot);
if (!region) {
failed = true;
return;
ph_load_result = KResult(-ENOMEM);
return IterationDecision::Break;
}
region->set_shared(true);
if (program_header.offset() == 0)
load_base_address = (FlatPtr)region->vaddr().as_ptr();
}
return IterationDecision::Continue;
});
if (failed) {
dbgln("do_exec: Failure loading program");
return KResult(-ENOEXEC);
if (ph_load_result.is_error()) {
dbgln("do_exec: Failure loading program ({})", ph_load_result.error());
return ph_load_result;
}
if (!elf_image.entry().offset(load_offset).get()) {

3
Libraries/LibELF/DynamicLoader.cpp
View file

@ -101,6 +101,7 @@ RefPtr<DynamicObject> DynamicLoader::dynamic_object_from_image() const
if (program_header.type() == PT_DYNAMIC) {
dynamic_section_address = VirtualAddress(program_header.raw_data());
}
return IterationDecision::Continue;
});
ASSERT(!dynamic_section_address.is_null());
@ -114,6 +115,7 @@ size_t DynamicLoader::calculate_tls_size() const
if (program_header.type() == PT_TLS) {
tls_size = program_header.size_in_memory();
}
return IterationDecision::Continue;
});
return tls_size;
}
@ -232,6 +234,7 @@ void DynamicLoader::load_program_headers()
} else if (region.is_dynamic()) {
dynamic_region_desired_vaddr = region.desired_load_address();
}
return IterationDecision::Continue;
});
ASSERT(text_region_ptr && data_region_ptr);

1
Libraries/LibELF/Image.cpp
View file

@ -108,6 +108,7 @@ void Image::dump() const
dbgprintf(" flags: %x\n", program_header.flags());
dbgprintf(" \n");
dbgprintf(" }\n");
return IterationDecision::Continue;
});
for (unsigned i = 0; i < header().e_shnum; ++i) {

6
Libraries/LibELF/Image.h
View file

@ -287,8 +287,10 @@ template<typename F>
inline void Image::for_each_program_header(F func) const
{
auto program_header_count = this->program_header_count();
for (unsigned i = 0; i < program_header_count; ++i)
func(program_header(i));
for (unsigned i = 0; i < program_header_count; ++i) {
if (func(program_header(i)) == IterationDecision::Break)
return;
}
}
} // end namespace ELF