This achieves two things:
- Programs can now intentionally perform arbitrary syscalls by calling
syscall(). This allows us to work on things like syscall fuzzing.
- It restricts the ability of userspace to make syscalls to a single
4KB page of code. In order to call the kernel directly, an attacker
must now locate this page and call through it.
These changes are arbitrarily divided into multiple commits to make it
easier to find potentially introduced bugs with git bisect.Everything:
The modifications in this commit were automatically made using the
following command:
find . -name '*.cpp' -exec sed -i -E 's/dbg\(\) << ("[^"{]*");/dbgln\(\1\);/' {} \;
We now configure the gcc spec files to use a different crt files for
static & PIE binaries.
This relieves us from the need to explicitly specify the desired crt0
file in cmake scripts.
Problem:
- If `fork()` fails the system tries to call `execl()`. That will
either succeed and replace the running process image or it will fail
and it needs to try again. The `if` is redundant because it will
only be evaluated if `execl()` fails.
Solution:
- Remove the `if`.
And also mark strlcpy() and strlcat() with __attribute__((warn_unused_result)).
Since our code is warning-free, this ensures we never misuse those functions.
(Or are very sure about doing it when turning off the warning for a particular
piece of code.)
The SI prefixes "k", "M", "G" mean "10^3", "10^6", "10^9".
The IEC prefixes "Ki", "Mi", "Gi" mean "2^10", "2^20", "2^30".
Let's use the correct name, at least in code.
Only changes the name of the constants, no other behavior change.
This enables a nice warning in case a function becomes dead code. Also,
in the case of test-crypto.cpp, I took the liberty to add the prefix 'g_'
to the global event loop.
Technically, this can be 'exploited' to set the pgid of an exploiting process
to a near-arbitrary new pgid. This can cause conflicts when assigning future pgids,
destroys the session-boundary, and might confuse future pgid-to-session lookups.
In practice, I can't come up with a way that this causes actual harm.
