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Kernel: Make sure the kernel info page is read-only for userspace

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To enforce this, we create two separate mappings of the same underlying
physical page. A writable mapping for the kernel, and a read-only one
for userspace (the one returned by sys$get_kernel_info_page.)
This commit is contained in:
Andreas Kling 2019-12-15 22:21:28 +01:00
parent 77cf607cda
commit 0a75a46501
3 changed files with 26 additions and 7 deletions
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21
Kernel/Process.cpp
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@ -58,7 +58,8 @@ static pid_t next_pid;
InlineLinkedList<Process>* g_processes;
static String* s_hostname;
static Lock* s_hostname_lock;
static VirtualAddress s_info_page_address;
static VirtualAddress s_info_page_address_for_userspace;
static VirtualAddress s_info_page_address_for_kernel;
VirtualAddress g_return_to_ring3_from_signal_trampoline;
VirtualAddress g_return_to_ring0_from_signal_trampoline;
HashMap<String, OwnPtr<Module>>* g_modules;
@ -78,7 +79,7 @@ void Process::initialize()
void Process::update_info_page_timestamp(const timeval& tv)
{
auto* info_page = (KernelInfoPage*)s_info_page_address.as_ptr();
auto* info_page = (KernelInfoPage*)s_info_page_address_for_kernel.as_ptr();
info_page->serial++;
const_cast<timeval&>(info_page->now) = tv;
}
@ -994,9 +995,15 @@ void create_signal_trampolines()
void create_kernel_info_page()
{
auto* info_page_region = MM.allocate_user_accessible_kernel_region(PAGE_SIZE, "Kernel info page").leak_ptr();
s_info_page_address = info_page_region->vaddr();
memset(s_info_page_address.as_ptr(), 0, PAGE_SIZE);
auto* info_page_region_for_userspace = MM.allocate_user_accessible_kernel_region(PAGE_SIZE, "Kernel info page").leak_ptr();
auto* info_page_region_for_kernel = MM.allocate_kernel_region_with_vmobject(info_page_region_for_userspace->vmobject(), PAGE_SIZE, "Kernel info page").leak_ptr();
s_info_page_address_for_userspace = info_page_region_for_userspace->vaddr();
s_info_page_address_for_kernel = info_page_region_for_kernel->vaddr();
memset(s_info_page_address_for_kernel.as_ptr(), 0, PAGE_SIZE);
info_page_region_for_userspace->set_writable(false);
info_page_region_for_userspace->remap();
}
int Process::sys$restore_signal_mask(u32 mask)
@ -1700,7 +1707,7 @@ int Process::sys$sleep(unsigned seconds)
timeval kgettimeofday()
{
return const_cast<const timeval&>(((KernelInfoPage*)s_info_page_address.as_ptr())->now);
return const_cast<const timeval&>(((KernelInfoPage*)s_info_page_address_for_kernel.as_ptr())->now);
}
void kgettimeofday(timeval& tv)
@ -3751,5 +3758,5 @@ int Process::sys$profiling_disable(pid_t pid)
void* Process::sys$get_kernel_info_page()
{
return s_info_page_address.as_ptr();
return s_info_page_address_for_userspace.as_ptr();
}