From f56ccc32468ee7885d3a9175e7d2cb608d301521 Mon Sep 17 00:00:00 2001 From: Kevin Lourenco Date: Mon, 29 Dec 2025 17:13:21 +0100 Subject: [PATCH] mm/memtest: add underflow detection for size calculation The computation: end = start + (size - (start_phys_aligned - start_phys)) / incr could theoretically underflow if size < offset, leading to a massive iteration. Add VM_WARN_ON_ONCE() to detect cases where the region size is smaller than the alignment offset. While this should never happen in practice due to memblock guarantees, the warning helps catch potential bugs in early memory initialization code. Suggested-by: Mike Rapoport Signed-off-by: Kevin Lourenco Link: https://patch.msgid.link/20251229161321.9079-1-klourencodev@gmail.com Signed-off-by: Mike Rapoport (Microsoft) --- mm/memtest.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memtest.c b/mm/memtest.c index c2c609c39119..520d41534cfa 100644 --- a/mm/memtest.c +++ b/mm/memtest.c @@ -50,6 +50,8 @@ static void __init memtest(u64 pattern, phys_addr_t start_phys, phys_addr_t size start_bad = 0; last_bad = 0; + VM_WARN_ON_ONCE(size < start_phys_aligned - start_phys); + for (p = start; p < end; p++) WRITE_ONCE(*p, pattern); -- 2.47.3