UPSTREAM: mm: vmalloc: support more granular vrealloc() sizing

commit a0309faf upstream.

Introduce struct vm_struct::requested_size so that the requested
(re)allocation size is retained separately from the allocated area size.
This means that KASAN will correctly poison the correct spans of requested
bytes.  This also means we can support growing the usable portion of an
allocation that can already be supported by the existing area's existing
allocation.

Link: https://lkml.kernel.org/r/20250426001105.it.679-kees@kernel.org


Fixes: 3ddc2fef ("mm: vmalloc: implement vrealloc()")
Change-Id: I81b617cd3002f87c061d436db779844785df639c
Signed-off-by: Kees Cook <kees@kernel.org>
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Closes: https://lore.kernel.org/all/20250408192503.6149a816@outsider.home/


Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 2910019b)
Bug: 437846539
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>