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LibELF: Fail gracefully when IFUNC resolver's object has textrels

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.text sections of objects that contain textrels have to be writable
during the relocation procedure. Because of this, we would segfault if
we tried to execute IFUNC resolvers defined in them. Let's print a
meaningful error message instead.

Additionally, a warning is now printed when we load objects with
textrels, as in the future, additional security mitigations might
interfere with them being loaded.
This commit is contained in:
Daniel Bertalan 2022-03-13 09:13:50 +01:00 • committed by Andreas Kling
parent 08c459e495
commit 7aca408993
1 changed files with 13 additions and 1 deletions
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14
Userland/Libraries/LibELF/DynamicLoader.cpp
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@ -162,6 +162,7 @@ bool DynamicLoader::load_stage_2(unsigned flags)
VERIFY(flags & RTLD_GLOBAL);
if (m_dynamic_object->has_text_relocations()) {
dbgln("\033[33mWarning:\033[0m Dynamic object {} has text relocations", m_dynamic_object->filename());
for (auto& text_segment : m_text_segments) {
VERIFY(text_segment.address().get() != 0);
@ -488,8 +489,13 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
symbol_location = VirtualAddress { (FlatPtr)0 };
} else {
symbol_location = res.value().address;
if (res.value().type == STT_GNU_IFUNC)
if (res.value().type == STT_GNU_IFUNC) {
if (res.value().dynamic_object != nullptr && res.value().dynamic_object->has_text_relocations()) {
dbgln("\033[31mError:\033[0m Refusing to call IFUNC resolver defined in an object with text relocations.");
return RelocationResult::Failed;
}
symbol_location = call_ifunc_resolver(symbol_location);
}
}
VERIFY(symbol_location != m_dynamic_object->base_address());
*patch_ptr = symbol_location.get();
@ -562,6 +568,12 @@ DynamicLoader::RelocationResult DynamicLoader::do_relocation(const ELF::DynamicO
resolver = m_dynamic_object->base_address().offset(relocation.addend());
else
resolver = m_dynamic_object->base_address().offset(*patch_ptr);
if (m_dynamic_object->has_text_relocations()) {
dbgln("\033[31mError:\033[0m Refusing to call IFUNC resolver defined in an object with text relocations.");
return RelocationResult::Failed;
}
*patch_ptr = call_ifunc_resolver(resolver).get();
break;
}