CVE-2026-89639

In the Linux kernel, the following vulnerability has been resolved:

cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC

cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it

cannot use cifs_resize_file_locked() to perform a proper fscache cookie

resize. Instead, add cifs_invalidate_cache() after cifs_setsize().

cifs_invalidate_cache() calls fscache_invalidate(), which works without

holding i_rwsem: it unconditionally increments inval_counter and sets

FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not

served once the cookie is later activated by fscache_use_cookie().

Truncation to zero leaves no valid cached data, making invalidation the

correct semantic here.