UBUNTU-CVE-2026-98683: Low severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: smb: client: flush dirty data before zeroing a range smb3zerorange() emulates FALLOCFLZERORANGE by invalidating the page cache over the target range with truncatepagecacherange() and then issuing FSCTLSETZERODATA to the server. Dirty data was only flushed conditionally, when the range reached or extended EOF. For a purely interior zero range that does not reach EOF, no flush happened, so a dirty folio overlapping the range could be written back to the server after the FSCTL and refill the range that was just zeroed with stale data. Fix this by unconditionally flushing and waiting for dirty data in the range before invalidating the page cache and issuing FSCTLSETZERODATA, exactly as was done for smb3punchhole() in commit d7d2adcd022b ("smb/client: flush dirty data before punching a hole"); the two paths are structurally identical here. This is observed as generic/363 randomly reading stale data where a zeroed range is expected against Windows Server.