The previous architecture had a huge flaw: the pointer to the protected
data was itself unprotected, allowing you to overwrite it at any time.
This patch reorganizes the protected data so it's part of the Process
class itself. (Actually, it's a new ProcessBase helper class.)
We use the first 4 KB of Process objects themselves as the new storage
location for protected data. Then we make Process objects page-aligned
using MAKE_ALIGNED_ALLOCATED.
This allows us to easily turn on/off write-protection for everything in
the ProcessBase portion of Process. :^)
Thanks to @bugaevc for pointing out the flaw! This is still not perfect
but it's an improvement.
Process member variable like m_euid are very valuable targets for
kernel exploits and until now they have been writable at all times.
This patch moves m_euid along with a whole bunch of other members
into a new Process::ProtectedData struct. This struct is remapped
as read-only memory whenever we don't need to write to it.
This means that a kernel write primitive is no longer enough to
overwrite a process's effective UID, you must first unprotect the
protected data where the UID is stored. :^)
This returns ENOSYS if you are running in the real kernel, and some
other result if you are running in UserspaceEmulator.
There are other ways we could check if we're inside an emulator, but
it seemed easier to just ask. :^)
If we can't allocate a PerformanceEventBuffer to store the profiling
events, we now fail sys$profiling_enable() and sys$perf_event()
with ENOMEM instead of carrying on with a broken buffer.
I don't dare touch the multi-threading logic and locking mechanism, so it stays
timespec for now. However, this could and should be changed to AK::Time, and I
bet it will simplify the "increment_time_since_boot()" code.
fuzz-syscalls found a bunch of unaligned accesses into struct sigaction
via this syscall. This patch fixes that issue by porting the syscall
to Userspace<T> which we should have done anyway. :^)
Fixes#5500.
This is basically just for consistency, it's quite strange to see
multiple AK container types next to each other, some with and some
without the namespace prefix - we're 'using AK::Foo;' a lot and should
leverage that. :^)
This was necessary in the past when crash handling would modify
various global things, but all that stuff is long gone so we can
simplify crashes by leaving the interrupt flag alone.
Make more of the kernel compile in 64-bit mode, and make some things
pointer-size-agnostic (by using FlatPtr.)
There's a lot of work to do here before the kernel will even compile.
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
This is a new promise that guards access to mmap() with MAP_FIXED.
Fixed-address mappings are rarely used, but can be useful if you are
trying to groom the process address space for malicious purposes.
None of our programs need this at the moment, as the only user of
MAP_FIXED is DynamicLoader, but the fixed mappings are constructed
before the process has had a chance to pledge anything.
The signal trampoline was previously in kernelspace memory, but with
a special exception to make it user-accessible.
This patch moves it into each process's regular address space so we
can stop supporting user-allowed memory above 0xc0000000.
Add a per-process ptrace lock and use it to prevent ptrace access to a
process after it decides to commit to a new executable in sys$execve().
Fixes#5230.
This patch adds Space, a class representing a process's address space.
- Each Process has a Space.
- The Space owns the PageDirectory and all Regions in the Process.
This allows us to reorganize sys$execve() so that it constructs and
populates a new Space fully before committing to it.
Previously, we would construct the new address space while still
running in the old one, and encountering an error meant we had to do
tedious and error-prone rollback.
Those problems are now gone, replaced by what's hopefully a set of much
smaller problems and missing cleanups. :^)
This patch adds sys$msyscall() which is loosely based on an OpenBSD
mechanism for preventing syscalls from non-blessed memory regions.
It works similarly to pledge and unveil, you can call it as many
times as you like, and when you're finished, you call it with a null
pointer and it will stop accepting new regions from then on.
If a syscall later happens and doesn't originate from one of the
previously blessed regions, the kernel will simply crash the process.
This prevents sys$mmap() and sys$mprotect() from creating executable
memory mappings in pledged programs that don't have this promise.
Note that the dynamic loader runs before pledging happens, so it's
unaffected by this.
This broke with the change that gave each process a list of its own
threads. Since threads are removed slightly earlier from that list
during process teardown, we're not able to use it for generating
coredump backtraces. Fortunately we have the "threads for coredump"
list for just this purpose. :^)
Since each Process now has its own list of threads, we don't need
to treat colonel any different anymore. This also means that it
reports all kernel threads, not just the idle threads.
Rather than walking all Thread instances and putting them into
a vector to be sorted by priority, queue them into priority sorted
linked lists as soon as they become ready to be executed.
Change Thread::current to be a static function and read using the fs
register, which eliminates a window between Processor::current()
returning and calling a function on it, which can trigger preemption
and a move to a different processor, which then causes operating
on the wrong object.
We now move the execpromises state into the regular promises, and clear
the execpromises state.
Also make sure to duplicate the promise state on fork.
This fixes an issue where "su" would launch a shell which immediately
crashed due to not having pledged "stdio".
Let's force callers to provide a VM range when allocating a region.
This makes ENOMEM error handling more visible and removes implicit
VM allocation which felt a bit magical.
This tells the kernel that the process wants to use pledge, but without
pledging anything - effectively restricting it to syscalls that don't
require a certain promise. This is part of OpenBSD's pledge() as well,
which served as basis for Serenity's.
Similar to LibC storing an assertion message before aborting, process
death by pledge violation now sets a "pledge_violation" key with the
respective pledge name as value in its coredump metadata, which the
CrashReporter will then show.
