* [PATCH] arm64: kvm: avoid overflow in integer division
@ 2023-05-17 20:23 Arnd Bergmann
2023-05-18 7:30 ` Marc Zyngier
2023-05-18 17:45 ` Oliver Upton
0 siblings, 2 replies; 4+ messages in thread
From: Arnd Bergmann @ 2023-05-17 20:23 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Shaoqin Huang, Ricardo Koller, Gavin Shan
Cc: Arnd Bergmann, James Morse, Suzuki K Poulose, Zenghui Yu,
Cornelia Huck, linux-arm-kernel, kvmarm, linux-kernel
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;
}
--
2.39.2
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^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] arm64: kvm: avoid overflow in integer division
2023-05-17 20:23 [PATCH] arm64: kvm: avoid overflow in integer division Arnd Bergmann
@ 2023-05-18 7:30 ` Marc Zyngier
2023-05-18 12:14 ` Arnd Bergmann
2023-05-18 17:45 ` Oliver Upton
1 sibling, 1 reply; 4+ messages in thread
From: Marc Zyngier @ 2023-05-18 7:30 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Oliver Upton, Catalin Marinas, Will Deacon, Shaoqin Huang,
Ricardo Koller, Gavin Shan, Arnd Bergmann, James Morse,
Suzuki K Poulose, Zenghui Yu, Cornelia Huck, linux-arm-kernel,
kvmarm, linux-kernel
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.
--
Without deviation from the norm, progress is not possible.
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] arm64: kvm: avoid overflow in integer division
2023-05-18 7:30 ` Marc Zyngier
@ 2023-05-18 12:14 ` Arnd Bergmann
0 siblings, 0 replies; 4+ messages in thread
From: Arnd Bergmann @ 2023-05-18 12:14 UTC (permalink / raw)
To: Marc Zyngier, Arnd Bergmann
Cc: Oliver Upton, Catalin Marinas, Will Deacon, Shaoqin Huang,
Ricardo Koller, Gavin Shan, James Morse, Suzuki K Poulose,
Zenghui Yu, Cornelia Huck, linux-arm-kernel, kvmarm, linux-kernel
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
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: kvm: avoid overflow in integer division
2023-05-17 20:23 [PATCH] arm64: kvm: avoid overflow in integer division Arnd Bergmann
2023-05-18 7:30 ` Marc Zyngier
@ 2023-05-18 17:45 ` Oliver Upton
1 sibling, 0 replies; 4+ messages in thread
From: Oliver Upton @ 2023-05-18 17:45 UTC (permalink / raw)
To: Gavin Shan, Marc Zyngier, Catalin Marinas, Shaoqin Huang,
Ricardo Koller, Will Deacon, Arnd Bergmann
Cc: Oliver Upton, Arnd Bergmann, kvmarm, Cornelia Huck, linux-kernel,
Zenghui Yu, Suzuki K Poulose, James Morse, linux-arm-kernel
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
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-05-17 20:23 [PATCH] arm64: kvm: avoid overflow in integer division Arnd Bergmann
2023-05-18 7:30 ` Marc Zyngier
2023-05-18 12:14 ` Arnd Bergmann
2023-05-18 17:45 ` Oliver Upton
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