From e05986ee7a5814bec0e0075d813daca3d46e4a9e Mon Sep 17 00:00:00 2001 From: Kalesh Singh Date: Tue, 29 Dec 2020 15:14:40 -0800 Subject: [PATCH] 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/20201219170433.2418867-1-kaleshsingh@google.com Fixes: c49dd34018026 ("mm: speedup mremap on 1GB or larger regions") Signed-off-by: Kalesh Singh Reported-by: Guenter Roeck Tested-by: Guenter Roeck Cc: Suren Baghdasaryan Cc: Minchan Kim Cc: Lokesh Gidra Cc: Helge Deller Cc: Kalesh Singh Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mremap.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/mremap.c b/mm/mremap.c index c5590afe7165..f554320281cc 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -358,7 +358,9 @@ static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr, next = (old_addr + size) & mask; /* even if next overflowed, extent below will be ok */ - extent = (next > old_end) ? old_end - old_addr : next - old_addr; + extent = next - old_addr; + if (extent > old_end - old_addr) + extent = old_end - old_addr; next = (new_addr + size) & mask; if (extent > next - new_addr) extent = next - new_addr; -- 2.20.1