mm/mremap.c: fix extent calculation

When `next < old_addr`, `next - old_addr` arithmetic underflows causing
`extent` to be incorrect.

Make `extent` the smaller of `next - old_addr` or `old_end - old_addr`.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: c49dd34018026 ("mm: speedup mremap on 1GB or larger regions")
Signed-off-by: Kalesh Singh <[email protected]>
Reported-by: Guenter Roeck <[email protected]>
Tested-by: Guenter Roeck <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Lokesh Gidra <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Kalesh Singh <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions