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mm/memtest: add underflow detection for size calculation

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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 <rppt@kernel.org>
Signed-off-by: Kevin Lourenco <klourencodev@gmail.com>
Link: https://patch.msgid.link/20251229161321.9079-1-klourencodev@gmail.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
This commit is contained in:
Kevin Lourenco 2025-12-29 17:13:21 +01:00 • committed by Mike Rapoport (Microsoft)
parent 58e3e52654
commit f56ccc3246
1 changed files with 2 additions and 0 deletions
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2
mm/memtest.c
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@ -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);