| Message ID | 20230517202352.793673-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: kvm: avoid overflow in integer division | expand |
On Wed, 17 May 2023 21:23:39 +0100, Arnd Bergmann <arnd@kernel.org> wrote: > > From: Arnd Bergmann <arnd@arndb.de> > > 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: e7bf7a490c68 ("KVM: arm64: Split huge pages when dirty logging is enabled") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > arch/arm64/kvm/mmu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 3386bd28d267..6db9ef288ec3 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -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; > } This is against -next, right? Oliver, I assume you'll take this as a fix for Ricardo's series? Thanks, M.
On Thu, May 18, 2023, at 09:30, Marc Zyngier wrote: > On Wed, 17 May 2023 21:23:39 +0100, > Arnd Bergmann <arnd@kernel.org> wrote: >> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c >> index 3386bd28d267..6db9ef288ec3 100644 >> --- a/arch/arm64/kvm/mmu.c >> +++ b/arch/arm64/kvm/mmu.c >> @@ -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; >> } > > This is against -next, right? Oliver, I assume you'll take this as a > fix for Ricardo's series? Yes, correct, I saw it after rebasing my tree from 6.4-rc2 to the latest -next. Arnd
On Wed, 17 May 2023 22:23:39 +0200, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > 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); > | ^~~~~~~~~~~~~~~~ > > [...] Applied to kvmarm/next, thanks! [1/1] arm64: kvm: avoid overflow in integer division https://git.kernel.org/kvmarm/kvmarm/c/14c3555f055d -- Best, Oliver
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 3386bd28d267..6db9ef288ec3 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -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; }