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ladybird/Kernel/Syscalls/mmap.cpp
Andreas Kling c3351d4b9f Kernel: Make VirtualFileSystem functions take credentials as input 
Instead of getting credentials from Process::current(), we now require
that they be provided as input to the various VFS functions.

This ensures that an atomic set of credentials is used throughout an
entire VFS operation.
2022-08-21 16:02:24 +02:00

608 lines
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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <Kernel/Arch/SafeMem.h>
#include <Kernel/Arch/SmapDisabler.h>
#include <Kernel/Arch/x86/MSR.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/Memory/AnonymousVMObject.h>
#include <Kernel/Memory/MemoryManager.h>
#include <Kernel/Memory/PageDirectory.h>
#include <Kernel/Memory/PrivateInodeVMObject.h>
#include <Kernel/Memory/Region.h>
#include <Kernel/Memory/SharedInodeVMObject.h>
#include <Kernel/PerformanceEventBuffer.h>
#include <Kernel/PerformanceManager.h>
#include <Kernel/Process.h>
#include <LibC/limits.h>
#include <LibELF/Validation.h>
namespace Kernel {
static bool should_make_executable_exception_for_dynamic_loader(bool make_readable, bool make_writable, bool make_executable, Memory::Region const& region)
{
// Normally we don't allow W -> X transitions, but we have to make an exception
// for the dynamic loader, which needs to do this after performing text relocations.
// FIXME: Investigate whether we could get rid of all text relocations entirely.
// The exception is only made if all the following criteria is fulfilled:
// The region must be RW
if (!(region.is_readable() && region.is_writable() && !region.is_executable()))
return false;
// The region wants to become RX
if (!(make_readable && !make_writable && make_executable))
return false;
// The region is backed by a file
if (!region.vmobject().is_inode())
return false;
// The file mapping is private, not shared (no relocations in a shared mapping!)
if (!region.vmobject().is_private_inode())
return false;
auto const& inode_vm = static_cast<Memory::InodeVMObject const&>(region.vmobject());
auto const& inode = inode_vm.inode();
ElfW(Ehdr) header;
auto buffer = UserOrKernelBuffer::for_kernel_buffer((u8*)&header);
auto result = inode.read_bytes(0, sizeof(header), buffer, nullptr);
if (result.is_error() || result.value() != sizeof(header))
return false;
// The file is a valid ELF binary
if (!ELF::validate_elf_header(header, inode.size()))
return false;
// The file is an ELF shared object
if (header.e_type != ET_DYN)
return false;
// FIXME: Are there any additional checks/validations we could do here?
return true;
}
ErrorOr<void> Process::validate_mmap_prot(int prot, bool map_stack, bool map_anonymous, Memory::Region const* region) const
{
bool make_readable = prot & PROT_READ;
bool make_writable = prot & PROT_WRITE;
bool make_executable = prot & PROT_EXEC;
if (map_anonymous && make_executable && !(executable()->mount_flags() & MS_AXALLOWED))
return EINVAL;
if (map_stack && make_executable)
return EINVAL;
if (executable()->mount_flags() & MS_WXALLOWED)
return {};
if (make_writable && make_executable)
return EINVAL;
if (region) {
if (make_writable && region->has_been_executable())
return EINVAL;
if (make_executable && region->has_been_writable()) {
if (should_make_executable_exception_for_dynamic_loader(make_readable, make_writable, make_executable, *region)) {
return {};
} else {
return EINVAL;
};
}
}
return {};
}
ErrorOr<void> Process::validate_inode_mmap_prot(int prot, Inode const& inode, bool map_shared) const
{
auto credentials = this->credentials();
auto metadata = inode.metadata();
if ((prot & PROT_READ) && !metadata.may_read(credentials))
return EACCES;
if (map_shared) {
// FIXME: What about readonly filesystem mounts? We cannot make a
// decision here without knowing the mount flags, so we would need to
// keep a Custody or something from mmap time.
if ((prot & PROT_WRITE) && !metadata.may_write(credentials))
return EACCES;
if (auto shared_vmobject = inode.shared_vmobject()) {
if ((prot & PROT_EXEC) && shared_vmobject->writable_mappings())
return EACCES;
if ((prot & PROT_WRITE) && shared_vmobject->executable_mappings())
return EACCES;
}
}
return {};
}
ErrorOr<FlatPtr> Process::sys$mmap(Userspace<Syscall::SC_mmap_params const*> user_params)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
auto params = TRY(copy_typed_from_user(user_params));
auto addr = (FlatPtr)params.addr;
auto size = params.size;
auto alignment = params.alignment ? params.alignment : PAGE_SIZE;
auto prot = params.prot;
auto flags = params.flags;
auto fd = params.fd;
auto offset = params.offset;
if (prot & PROT_EXEC) {
TRY(require_promise(Pledge::prot_exec));
}
if (prot & MAP_FIXED || prot & MAP_FIXED_NOREPLACE) {
TRY(require_promise(Pledge::map_fixed));
}
if (alignment & ~PAGE_MASK)
return EINVAL;
size_t rounded_size = TRY(Memory::page_round_up(size));
if (!Memory::is_user_range(VirtualAddress(addr), rounded_size))
return EFAULT;
OwnPtr<KString> name;
if (params.name.characters) {
if (params.name.length > PATH_MAX)
return ENAMETOOLONG;
name = TRY(try_copy_kstring_from_user(params.name));
}
if (size == 0)
return EINVAL;
if ((FlatPtr)addr & ~PAGE_MASK)
return EINVAL;
bool map_shared = flags & MAP_SHARED;
bool map_anonymous = flags & MAP_ANONYMOUS;
bool map_private = flags & MAP_PRIVATE;
bool map_stack = flags & MAP_STACK;
bool map_fixed = flags & MAP_FIXED;
bool map_noreserve = flags & MAP_NORESERVE;
bool map_randomized = flags & MAP_RANDOMIZED;
bool map_fixed_noreplace = flags & MAP_FIXED_NOREPLACE;
if (map_shared && map_private)
return EINVAL;
if (!map_shared && !map_private)
return EINVAL;
if ((map_fixed || map_fixed_noreplace) && map_randomized)
return EINVAL;
TRY(validate_mmap_prot(prot, map_stack, map_anonymous));
if (map_stack && (!map_private || !map_anonymous))
return EINVAL;
Memory::Region* region = nullptr;
// If MAP_FIXED is specified, existing mappings that intersect the requested range are removed.
if (map_fixed)
TRY(address_space().unmap_mmap_range(VirtualAddress(addr), size));
Memory::VirtualRange requested_range { VirtualAddress { addr }, rounded_size };
if (addr && !(map_fixed || map_fixed_noreplace)) {
// If there's an address but MAP_FIXED wasn't specified, the address is just a hint.
requested_range = { {}, rounded_size };
}
if (map_anonymous) {
auto strategy = map_noreserve ? AllocationStrategy::None : AllocationStrategy::Reserve;
LockRefPtr<Memory::AnonymousVMObject> vmobject;
if (flags & MAP_PURGEABLE) {
vmobject = TRY(Memory::AnonymousVMObject::try_create_purgeable_with_size(rounded_size, strategy));
} else {
vmobject = TRY(Memory::AnonymousVMObject::try_create_with_size(rounded_size, strategy));
}
region = TRY(address_space().allocate_region_with_vmobject(map_randomized ? Memory::RandomizeVirtualAddress::Yes : Memory::RandomizeVirtualAddress::No, requested_range.base(), requested_range.size(), alignment, vmobject.release_nonnull(), 0, {}, prot, map_shared));
} else {
if (offset < 0)
return EINVAL;
if (static_cast<size_t>(offset) & ~PAGE_MASK)
return EINVAL;
auto description = TRY(open_file_description(fd));
if (description->is_directory())
return ENODEV;
// Require read access even when read protection is not requested.
if (!description->is_readable())
return EACCES;
if (map_shared) {
if ((prot & PROT_WRITE) && !description->is_writable())
return EACCES;
}
if (description->inode())
TRY(validate_inode_mmap_prot(prot, *description->inode(), map_shared));
region = TRY(description->mmap(*this, requested_range, static_cast<u64>(offset), prot, map_shared));
}
if (!region)
return ENOMEM;
region->set_mmap(true);
if (map_shared)
region->set_shared(true);
if (map_stack)
region->set_stack(true);
if (name)
region->set_name(move(name));
PerformanceManager::add_mmap_perf_event(*this, *region);
return region->vaddr().get();
}
ErrorOr<FlatPtr> Process::sys$mprotect(Userspace<void*> addr, size_t size, int prot)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
if (prot & PROT_EXEC) {
TRY(require_promise(Pledge::prot_exec));
}
auto range_to_mprotect = TRY(Memory::expand_range_to_page_boundaries(addr.ptr(), size));
if (!range_to_mprotect.size())
return EINVAL;
if (!is_user_range(range_to_mprotect))
return EFAULT;
if (auto* whole_region = address_space().find_region_from_range(range_to_mprotect)) {
if (!whole_region->is_mmap())
return EPERM;
TRY(validate_mmap_prot(prot, whole_region->is_stack(), whole_region->vmobject().is_anonymous(), whole_region));
if (whole_region->access() == Memory::prot_to_region_access_flags(prot))
return 0;
if (whole_region->vmobject().is_inode())
TRY(validate_inode_mmap_prot(prot, static_cast<Memory::InodeVMObject const&>(whole_region->vmobject()).inode(), whole_region->is_shared()));
whole_region->set_readable(prot & PROT_READ);
whole_region->set_writable(prot & PROT_WRITE);
whole_region->set_executable(prot & PROT_EXEC);
whole_region->remap();
return 0;
}
// Check if we can carve out the desired range from an existing region
if (auto* old_region = address_space().find_region_containing(range_to_mprotect)) {
if (!old_region->is_mmap())
return EPERM;
TRY(validate_mmap_prot(prot, old_region->is_stack(), old_region->vmobject().is_anonymous(), old_region));
if (old_region->access() == Memory::prot_to_region_access_flags(prot))
return 0;
if (old_region->vmobject().is_inode())
TRY(validate_inode_mmap_prot(prot, static_cast<Memory::InodeVMObject const&>(old_region->vmobject()).inode(), old_region->is_shared()));
// Remove the old region from our regions tree, since were going to add another region
// with the exact same start address.
auto region = address_space().take_region(*old_region);
region->unmap();
// This vector is the region(s) adjacent to our range.
// We need to allocate a new region for the range we wanted to change permission bits on.
auto adjacent_regions = TRY(address_space().try_split_region_around_range(*region, range_to_mprotect));
size_t new_range_offset_in_vmobject = region->offset_in_vmobject() + (range_to_mprotect.base().get() - region->range().base().get());
auto* new_region = TRY(address_space().try_allocate_split_region(*region, range_to_mprotect, new_range_offset_in_vmobject));
new_region->set_readable(prot & PROT_READ);
new_region->set_writable(prot & PROT_WRITE);
new_region->set_executable(prot & PROT_EXEC);
// Map the new regions using our page directory (they were just allocated and don't have one).
for (auto* adjacent_region : adjacent_regions) {
TRY(adjacent_region->map(address_space().page_directory()));
}
TRY(new_region->map(address_space().page_directory()));
return 0;
}
if (auto const& regions = TRY(address_space().find_regions_intersecting(range_to_mprotect)); regions.size()) {
size_t full_size_found = 0;
// Check that all intersecting regions are compatible.
for (auto const* region : regions) {
if (!region->is_mmap())
return EPERM;
TRY(validate_mmap_prot(prot, region->is_stack(), region->vmobject().is_anonymous(), region));
if (region->vmobject().is_inode())
TRY(validate_inode_mmap_prot(prot, static_cast<Memory::InodeVMObject const&>(region->vmobject()).inode(), region->is_shared()));
full_size_found += region->range().intersect(range_to_mprotect).size();
}
if (full_size_found != range_to_mprotect.size())
return ENOMEM;
// Finally, iterate over each region, either updating its access flags if the range covers it wholly,
// or carving out a new subregion with the appropriate access flags set.
for (auto* old_region : regions) {
if (old_region->access() == Memory::prot_to_region_access_flags(prot))
continue;
auto const intersection_to_mprotect = range_to_mprotect.intersect(old_region->range());
// If the region is completely covered by range, simply update the access flags
if (intersection_to_mprotect == old_region->range()) {
old_region->set_readable(prot & PROT_READ);
old_region->set_writable(prot & PROT_WRITE);
old_region->set_executable(prot & PROT_EXEC);
old_region->remap();
continue;
}
// Remove the old region from our regions tree, since were going to add another region
// with the exact same start address.
auto region = address_space().take_region(*old_region);
region->unmap();
// This vector is the region(s) adjacent to our range.
// We need to allocate a new region for the range we wanted to change permission bits on.
auto adjacent_regions = TRY(address_space().try_split_region_around_range(*old_region, intersection_to_mprotect));
// Since the range is not contained in a single region, it can only partially cover its starting and ending region,
// therefore carving out a chunk from the region will always produce a single extra region, and not two.
VERIFY(adjacent_regions.size() == 1);
size_t new_range_offset_in_vmobject = old_region->offset_in_vmobject() + (intersection_to_mprotect.base().get() - old_region->range().base().get());
auto* new_region = TRY(address_space().try_allocate_split_region(*region, intersection_to_mprotect, new_range_offset_in_vmobject));
new_region->set_readable(prot & PROT_READ);
new_region->set_writable(prot & PROT_WRITE);
new_region->set_executable(prot & PROT_EXEC);
// Map the new region using our page directory (they were just allocated and don't have one) if any.
if (adjacent_regions.size())
TRY(adjacent_regions[0]->map(address_space().page_directory()));
TRY(new_region->map(address_space().page_directory()));
}
return 0;
}
return EINVAL;
}
ErrorOr<FlatPtr> Process::sys$madvise(Userspace<void*> address, size_t size, int advice)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
auto range_to_madvise = TRY(Memory::expand_range_to_page_boundaries(address.ptr(), size));
if (!range_to_madvise.size())
return EINVAL;
if (!is_user_range(range_to_madvise))
return EFAULT;
auto* region = address_space().find_region_from_range(range_to_madvise);
if (!region)
return EINVAL;
if (!region->is_mmap())
return EPERM;
if (advice == MADV_SET_VOLATILE || advice == MADV_SET_NONVOLATILE) {
if (!region->vmobject().is_anonymous())
return EINVAL;
auto& vmobject = static_cast<Memory::AnonymousVMObject&>(region->vmobject());
if (!vmobject.is_purgeable())
return EINVAL;
bool was_purged = false;
TRY(vmobject.set_volatile(advice == MADV_SET_VOLATILE, was_purged));
return was_purged ? 1 : 0;
}
return EINVAL;
}
ErrorOr<FlatPtr> Process::sys$set_mmap_name(Userspace<Syscall::SC_set_mmap_name_params const*> user_params)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
auto params = TRY(copy_typed_from_user(user_params));
if (params.name.length > PATH_MAX)
return ENAMETOOLONG;
auto name = TRY(try_copy_kstring_from_user(params.name));
auto range = TRY(Memory::expand_range_to_page_boundaries((FlatPtr)params.addr, params.size));
auto* region = address_space().find_region_from_range(range);
if (!region)
return EINVAL;
if (!region->is_mmap())
return EPERM;
region->set_name(move(name));
PerformanceManager::add_mmap_perf_event(*this, *region);
return 0;
}
ErrorOr<FlatPtr> Process::sys$munmap(Userspace<void*> addr, size_t size)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
TRY(address_space().unmap_mmap_range(addr.vaddr(), size));
return 0;
}
ErrorOr<FlatPtr> Process::sys$mremap(Userspace<Syscall::SC_mremap_params const*> user_params)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
auto params = TRY(copy_typed_from_user(user_params));
auto old_range = TRY(Memory::expand_range_to_page_boundaries((FlatPtr)params.old_address, params.old_size));
auto* old_region = address_space().find_region_from_range(old_range);
if (!old_region)
return EINVAL;
if (!old_region->is_mmap())
return EPERM;
if (old_region->vmobject().is_shared_inode() && params.flags & MAP_PRIVATE && !(params.flags & (MAP_ANONYMOUS | MAP_NORESERVE))) {
auto range = old_region->range();
auto old_prot = region_access_flags_to_prot(old_region->access());
auto old_offset = old_region->offset_in_vmobject();
NonnullLockRefPtr inode = static_cast<Memory::SharedInodeVMObject&>(old_region->vmobject()).inode();
auto new_vmobject = TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode));
auto old_name = old_region->take_name();
old_region->unmap();
address_space().deallocate_region(*old_region);
auto* new_region = TRY(address_space().allocate_region_with_vmobject(range, move(new_vmobject), old_offset, old_name->view(), old_prot, false));
new_region->set_mmap(true);
return new_region->vaddr().get();
}
dbgln("sys$mremap: Unimplemented remap request (flags={})", params.flags);
return ENOTIMPL;
}
ErrorOr<FlatPtr> Process::sys$allocate_tls(Userspace<char const*> initial_data, size_t size)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
if (!size || size % PAGE_SIZE != 0)
return EINVAL;
if (!m_master_tls_region.is_null())
return EEXIST;
if (thread_count() != 1)
return EFAULT;
Thread* main_thread = nullptr;
bool multiple_threads = false;
for_each_thread([&main_thread, &multiple_threads](auto& thread) {
if (main_thread)
multiple_threads = true;
main_thread = &thread;
return IterationDecision::Break;
});
VERIFY(main_thread);
if (multiple_threads)
return EINVAL;
auto* region = TRY(address_space().allocate_region(Memory::RandomizeVirtualAddress::Yes, {}, size, PAGE_SIZE, "Master TLS"sv, PROT_READ | PROT_WRITE));
m_master_tls_region = TRY(region->try_make_weak_ptr());
m_master_tls_size = size;
m_master_tls_alignment = PAGE_SIZE;
{
Kernel::SmapDisabler disabler;
void* fault_at;
if (!Kernel::safe_memcpy((char*)m_master_tls_region.unsafe_ptr()->vaddr().as_ptr(), (char*)initial_data.ptr(), size, fault_at))
return EFAULT;
}
TRY(main_thread->make_thread_specific_region({}));
#if ARCH(I386)
auto& tls_descriptor = Processor::current().get_gdt_entry(GDT_SELECTOR_TLS);
tls_descriptor.set_base(main_thread->thread_specific_data());
tls_descriptor.set_limit(main_thread->thread_specific_region_size());
#else
MSR fs_base_msr(MSR_FS_BASE);
fs_base_msr.set(main_thread->thread_specific_data().get());
#endif
return m_master_tls_region.unsafe_ptr()->vaddr().get();
}
ErrorOr<FlatPtr> Process::sys$msyscall(Userspace<void*> address)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
if (address_space().enforces_syscall_regions())
return EPERM;
if (!address) {
address_space().set_enforces_syscall_regions(true);
return 0;
}
if (!Memory::is_user_address(address.vaddr()))
return EFAULT;
auto* region = address_space().find_region_containing(Memory::VirtualRange { address.vaddr(), 1 });
if (!region)
return EINVAL;
if (!region->is_mmap())
return EINVAL;
region->set_syscall_region(true);
return 0;
}
ErrorOr<FlatPtr> Process::sys$msync(Userspace<void*> address, size_t size, int flags)
{
if ((flags & (MS_SYNC | MS_ASYNC | MS_INVALIDATE)) != flags)
return EINVAL;
bool is_async = (flags & MS_ASYNC) == MS_ASYNC;
bool is_sync = (flags & MS_SYNC) == MS_SYNC;
if (is_sync == is_async)
return EINVAL;
if (address.ptr() % PAGE_SIZE != 0)
return EINVAL;
// Note: This is not specified
auto rounded_size = TRY(Memory::page_round_up(size));
auto regions = TRY(address_space().find_regions_intersecting(Memory::VirtualRange { address.vaddr(), rounded_size }));
// All regions from address upto address+size shall be mapped
if (regions.is_empty())
return ENOMEM;
size_t total_intersection_size = 0;
Memory::VirtualRange range_to_sync { address.vaddr(), rounded_size };
for (auto const* region : regions) {
// Region was not mapped
if (!region->is_mmap())
return ENOMEM;
total_intersection_size += region->range().intersect(range_to_sync).size();
}
// Part of the indicated range was not mapped
if (total_intersection_size != size)
return ENOMEM;
for (auto* region : regions) {
auto& vmobject = region->vmobject();
if (!vmobject.is_shared_inode())
continue;
off_t offset = region->offset_in_vmobject() + address.ptr() - region->range().base().get();
auto& inode_vmobject = static_cast<Memory::SharedInodeVMObject&>(vmobject);
// FIXME: If multiple regions belong to the same vmobject we might want to coalesce these writes
// FIXME: Handle MS_ASYNC
TRY(inode_vmobject.sync(offset / PAGE_SIZE, rounded_size / PAGE_SIZE));
// FIXME: Handle MS_INVALIDATE
}
return 0;
}
}
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