UBUNTU-CVE-2026-93167: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: csky: Fix a4/a5 restoration in syscall trace path The syscall trace path reloads syscall arguments from ptregs before calling the syscall handler. On C-SKY ABIv2, the 5th and 6th syscall arguments are prepared as stack arguments before invoking syscallid. The current code adjusts sp before loading LSAVEA4 and LSAVEA5. Since those offsets are relative to the original ptregs base, loading them after changing sp fetches the wrong slots. As a result, traced syscalls that use the 5th or 6th argument may receive corrupted arguments. This is visible with mmap2(), which takes six arguments. A small PTRACESYSCALL reproducer opens a file and maps one page with: mmap(NULL, 4096, PROTREAD | PROTEXEC, MAPPRIVATE, fd, 0) Before the fix, the traced child fails the mmap and exits with 12. After the fix, the mapping succeeds and the child exits with 0. Fix the trace path by loading a4/a5 from ptregs before changing sp. Tested on: ck860f, linux-4.19.15, C-SKY abiv2