Medium [CVE-2026-68098] bound DACL dedup walk to copied ACEs

In the Linux kernel, the following vulnerability has been resolved: ksmbd: bound DACL dedup walk to copied ACEs set_ntacl_dacl() can stop copying ACEs before consuming the full input DACL when size accounting overflows.

When that happens, num_aces reflects only the ACEs that were actually copied into the output DACL, but set_posix_acl_entries_dacl() still receives nt_num_aces and uses it to walk the existing ACE array during dedup. That makes the dedup walk scan past the copied ACE array and inspect buffer tail that does not contain valid ACEs.

Split the two meanings currently carried by the NT ACE count. Pass the number of copied NT ACEs to bound the dedup walk, and preserve the original "input DACL had NT ACEs" state separately for the Everyone/default ACL fallback.

This keeps the dedup walk aligned with the ACEs that are actually present in the rebuilt DACL. The `set_ntacl_dacl()` function, which processes Discretionary Access Control Lists (DACLs), can stop copying Access Control Entries (ACEs) prematurely due to a size accounting overflow.

This can cause a subsequent deduplication process to read beyond the intended memory buffer, potentially leading to an out-of-bounds read. This issue could result in a denial of service or information disclosure.

This issue affects ksmbd (in-kernel SMB server).