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arm64: kvm: avoid overflow in integer division

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The newly added kvm_mmu_split_nr_page_tables() function uses DIV_ROUND_DOWN_ULL()
to divide 64-bit addresses, but this requires a 32-bit divisior, and PUD_SIZE
may exceed that when 64KB pages are used:

arch/arm64/kvm/mmu.c: In function 'kvm_mmu_split_nr_page_tables':
include/linux/math.h:42:64: error: conversion from 'long unsigned int' to 'u32' {aka 'unsigned int'} changes value from '68719476736' to '0' [-Werror=overflow]
   42 |         DIV_ROUND_DOWN_ULL((unsigned long long)(ll) + (d) - 1, (d))
      |                                                                ^~~
include/linux/math.h:39:47: note: in definition of macro 'DIV_ROUND_DOWN_ULL'
   39 | #define DIV_ROUND_DOWN_ULL(ll, d) div_u64(ll, d)
      |                                               ^
arch/arm64/kvm/mmu.c:95:22: note: in expansion of macro 'DIV_ROUND_UP_ULL'
   95 |                 n += DIV_ROUND_UP_ULL(range, PUD_SIZE);
      |                      ^~~~~~~~~~~~~~~~

Since this code is only used on 64-bit targets, DIV_ROUND_UP() can deal with this
more easily, as it already takes 64-bit arguments.

Fixes: e7bf7a490c ("KVM: arm64: Split huge pages when dirty logging is enabled")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230517202352.793673-1-arnd@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Arnd Bergmann 2023-05-17 22:23:39 +02:00 committed by Oliver Upton
parent a12ab1378a
commit 14c3555f05
1 changed files with 2 additions and 2 deletions
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4
arch/arm64/kvm/mmu.c
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@ -92,8 +92,8 @@ static int kvm_mmu_split_nr_page_tables(u64 range)
int n = 0;
if (KVM_PGTABLE_MIN_BLOCK_LEVEL < 2)
n += DIV_ROUND_UP_ULL(range, PUD_SIZE);
n += DIV_ROUND_UP_ULL(range, PMD_SIZE);
n += DIV_ROUND_UP(range, PUD_SIZE);
n += DIV_ROUND_UP(range, PMD_SIZE);
return n;
}