ladybird/Tests
Ben Wiederhake 28e1da344d Kernel: Demonstrate race condition in clock_nanosleep
This adds a test for the race condition in clock_nanosleep.
The crux is that clock_nanosleep verifies that the output buffer
is writable *before* sleeping, and writes to it *after* sleeping.
In the meantime, a concurrent thread can make the output buffer
unwritable, e.g. by deallocating it.

This testcase is needlessly complex because pthread_kill is
not implemented yet.  I tried to keep it as simple as possible.

Here is the relevant part of dmesg:
[nanosleep-race-outbuf-munmap(22:22)]: Unblock nanosleep-race-outbuf-munmap(20:20) due to signal
nanosleep-race-outbuf-munmap(20:20) Unrecoverable page fault, write to address 0x02130016
CRASH: Page Fault. Process: nanosleep-race-outbuf-munmap(20)
[nanosleep-race-outbuf-munmap(20:20)]: 0xc01160ff  memcpy +44
[nanosleep-race-outbuf-munmap(20:20)]: 0xc014de64  Kernel::Process::crash(int, unsigned int) +782
[nanosleep-race-outbuf-munmap(20:20)]: 0xc01191b5  illegal_instruction_handler +0
[nanosleep-race-outbuf-munmap(20:20)]: 0xc011965b  page_fault_handler +649
[nanosleep-race-outbuf-munmap(20:20)]: 0xc0117233  page_fault_asm_entry +22
[nanosleep-race-outbuf-munmap(20:20)]: 0xc011616b  copy_to_user +102
[nanosleep-race-outbuf-munmap(20:20)]: 0xc015911f  Kernel::Process::sys(Kernel::Syscall::SC_clock_nanosleep_params const*) +457
[nanosleep-race-outbuf-munmap(20:20)]: 0xc015daad  syscall_handler +1130
[nanosleep-race-outbuf-munmap(20:20)]: 0xc015d597  syscall_asm_entry +29
[nanosleep-race-outbuf-munmap(20:20)]: 0x08048437  main +146
[nanosleep-race-outbuf-munmap(20:20)]: 0x08048573  _start +94

Most importantly, note that it crashes *inside*
Kernel::Process::sys.
Instead, the correct behavior is to return -EFAULT.
2020-03-03 20:13:32 +01:00
..
Kernel Kernel: Demonstrate race condition in clock_nanosleep 2020-03-03 20:13:32 +01:00
LibC LibC: The exec() family of functions should not search "." by default 2020-02-01 16:14:09 +01:00