Audit all syscalls for permissions and access checks

[waddlesplash]

Here's a full list of source files containing syscall implementations:

• OK src/system/kernel/arch/arm/arch_atomic32.cpp
• OK src/system/kernel/arch/arm/arch_atomic64.cpp
• OK src/system/kernel/arch/m68k/arch_atomic.cpp
• OK src/system/kernel/arch/x86/arch_system_info.cpp
• OK src/system/kernel/arch/x86/syscalls_compat.cpp
• OK src/system/kernel/debug/debug.cpp
• OK src/system/kernel/debug/frame_buffer_console.cpp
• OK src/system/kernel/debug/safemode_settings.cpp
• OK src/system/kernel/debug/system_profiler.cpp
• OK src/system/kernel/debug/tracing.cpp
• OK src/system/kernel/debug/user_debugger.cpp
• NEEDSWORK src/system/kernel/disk_device_manager/ddm_userland_interface.cpp
• OK src/system/kernel/UserTimer.cpp
• OK src/system/kernel/cpu.cpp
• OK src/system/kernel/elf.cpp
• OK src/system/kernel/fs/fd.cpp
• NEEDSWORK src/system/kernel/fs/node_monitor.cpp
• OK src/system/kernel/fs/socket.cpp
• OK src/system/kernel/fs/vfs.cpp (except #15701)
• src/system/kernel/image.cpp
• src/system/kernel/locks/user_mutex.cpp
• src/system/kernel/messaging/MessagingService.cpp
• src/system/kernel/port.cpp
• src/system/kernel/posix/realtime_sem.cpp
• src/system/kernel/posix/xsi_message_queue.cpp
• src/system/kernel/posix/xsi_semaphore.cpp
• src/system/kernel/real_time_clock.cpp
• src/system/kernel/scheduler/scheduler.cpp
• src/system/kernel/scheduler/scheduling_analysis.cpp
• src/system/kernel/sem.cpp
• src/system/kernel/shutdown.cpp
• src/system/kernel/signal.cpp
• src/system/kernel/syscalls.cpp
• src/system/kernel/system_info.cpp
• src/system/kernel/team.cpp
• src/system/kernel/thread.cpp
• src/system/kernel/usergroup.cpp
• src/system/kernel/vm/vm.cpp
• src/system/kernel/wait_for_objects.cpp

Each and every one of these needs to be audited, namely:

• All passed pointers are checked against IS_USER_ADDRESS (thanks to SMAP, largely already done)
• All objects (e.g. FDs, areas, semaphores) manipulated by syscalls are checked that the calling team has access to manipulate them
• Whatever other things I think of adding here...

[waddlesplash]

Did the first pass on the first few files.

safemode_settings does not do any access checks; any application is allowed to read (not write, that can't be done via syscall) safemode settings. I think that's OK? Otherwise the file is fine.

system_profiler also does not seem to do permissions checks. I think that we expose quite a lot of information in that, so it should probably only allow root to run the profiler?

[waddlesplash]

Just for the record: I already added thread syscall permissions checks in ​hrev52825~1, and the first level of VM area access checks in ​hrev52546~2.

[waddlesplash]

A bunch more files done in hrev53233.

[waddlesplash]

kernel/fs/fd done in hrev53481.

[kallisti5]

This one seems important, but is it a blocker for R1 Beta2? Seems more critical (something that could be fixed post-release in the branch)

[pulkomandy]

Yes, this does not deserve to be a blocker.

[waddlesplash]

vfs.cpp done in hrev53864, with one caveat.