idr: fix idr_alloc() returning an ID out of range

idr: fix idr_alloc() returning an ID out of range

If you use an IDR with a non-zero base, and specify a range that lies
entirely below the base, 'max - base' becomes very large and
idr_get_free() can return an ID that lies outside of the requested range.

Link: https://lkml.kernel.org/r/20251128161853.3200058-1-willy@infradead.org
Fixes: 6ce711f27500 ("idr: Make 1-based IDRs more efficient")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: Jan Sokolowski <jan.sokolowski@intel.com>
Reported-by: Koen Koning <koen.koning@intel.com>
Reported-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6449
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>