Comment 10 for bug 1863086

The commit has landed in 5.3.0-56-generic on eoan and 5.4.0-38-generic on focal, currently in -proposed.

Verification for each kernel:

I set the sysctl kernel.core_pattern to "|" with:

$ sudo sysctl kernel.core_pattern="|"

I then compiled the following reproducer:

int main()
{
    *(int*)33 = 33;

    return 0;
}

When running the program, we get a segfault, and the coredump handler kicks in, and we see the following in dmesg:

[ 34.025572] format_corename failed
[ 34.025572] Aborting core

This is a change in the original behaviour, but technically more correct than it used to be, since it simply bails out earlier in the coredump process than before when we confirm we have an invalid core_pattern name string.

The systems no longer get a null pointer dereference in the kernel, and no longer panic. The system keeps working as usual now.

I have confirmed the above on both 5.3.0-56-generic on eoan and 5.4.0-38-generic on focal, so I am happy to mark this as verified.