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LibELF: Map text segments read-only at first

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To support upcoming W^X changes in the kernel, the dynamic loader needs
to be careful about the order in which permissions are added to shared
library text segments.

We now start by mapping text segments read-only (no-write, no-exec).
If relocations are needed, we make them writable, and then finally,
for all text segments, we finish by making them read+exec.
This commit is contained in:
Andreas Kling 2021-01-29 14:36:46 +01:00
parent 3438b77aa4
commit d988bd86e4
1 changed files with 4 additions and 8 deletions
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12
Userland/Libraries/LibELF/DynamicLoader.cpp
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@ -209,18 +209,14 @@ void DynamicLoader::do_main_relocations(size_t total_tls_size)
RefPtr<DynamicObject> DynamicLoader::load_stage_3(unsigned flags, size_t total_tls_size)
{
do_lazy_relocations(total_tls_size);
if (flags & RTLD_LAZY) {
setup_plt_trampoline();
}
// Clean up our setting of .text to PROT_READ | PROT_WRITE
if (m_dynamic_object->has_text_relocations()) {
if (0 > mprotect(m_text_segment_load_address.as_ptr(), m_text_segment_size, PROT_READ | PROT_EXEC)) {
perror("mprotect .text: PROT_READ | PROT_EXEC"); // FIXME: dlerror?
return nullptr;
}
if (mprotect(m_text_segment_load_address.as_ptr(), m_text_segment_size, PROT_READ | PROT_EXEC) < 0) {
perror("mprotect .text: PROT_READ | PROT_EXEC"); // FIXME: dlerror?
return nullptr;
}
call_object_init_functions();
@ -296,7 +292,7 @@ void DynamicLoader::load_program_headers()
auto* text_segment_begin = (u8*)mmap_with_name(
requested_load_address,
total_mapping_size.value(),
text_region->mmap_prot(),
PROT_READ,
text_mmap_flags,
m_image_fd,
text_region->offset(),