NACK: [SRU][B/F:linux-kvm][PATCH v2 0/1] UBUNTU: [Config] kvm: Add support for modifying LDT

[Cory Todd]

On Mon, Mar 27, 2023 at 02:44:02PM +0200, Roxana Nicolescu wrote:
> BugLink: https://bugs.launchpad.net/bugs/2009442
> 
> SRU Justification:
> 
> [Impact]
> bionic/focal linux-kvm failure in glibc autopkgtest
> 
> FAIL: misc/tst-bz21269
> original exit status 1
> error: ../sysdeps/unix/sysv/linux/i386/tst-bz21269.c:55:
> not true: syscall (SYS_modify_ldt, 1, ptr, bytecount) == 0
> error: 1 test failures
> 
> Syscall modify_ldt is not enabled because
> CONFIG_MODIFY_LDT_SYSCALL=n for bionic/focal-kvm,
> even though generic and newer versions (even kvm derivativatives)
> have it enabled.
> 
> [Fix]
> Custom patch to bionic/focal-kvm to enable CONFIG_MODIFY_LDT_SYSCALL.
> 
> [Test Plan]
> Built on cbd and tested autopkgtest glibc locally in a vm.
> 
> [Where problems could occur]
> 1. Regression probability is pretty low, we are adding functionality
> not previously present but looking at jammy this test is fine.
> 2. Enabling this adds a small  overhead to context switches
> and increases the low level  kernel attack surface.
> 
> v2:
> 1. Modified the annotation file.
> 2. Set CONFIG_X86_16BIT=n to avoid getting the prompt that interrupts
> the build process.
> 
> Roxana Nicolescu (1):
>   UBUNTU: [Config] kvm: Add support for modifying LDT
> 

The annotations for bionic:linux-kvm need a second look. We see a
compilation error due to check-config.

check-config: FAIL (y != m): CONFIG_MODIFY_LDT_SYSCALL policy<{'amd64': 'm'}> mark<ENFORCED> note<LP: #2009442>

- corytodd