* [PATCH v1] drivers/vhost/vhost: fix overflow checks in vhost_overflow
@ 2022-12-07 13:46 Daniil Tatianin
2022-12-07 15:01 ` Michael S. Tsirkin
0 siblings, 1 reply; 3+ messages in thread
From: Daniil Tatianin @ 2022-12-07 13:46 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Daniil Tatianin, Jason Wang, kvm, virtualization, netdev, linux-kernel
The if statement would erroneously check for > ULONG_MAX, which could
never evaluate to true. Check for equality instead.
Found by Linux Verification Center (linuxtesting.org) with the SVACE
static analysis tool.
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
---
drivers/vhost/vhost.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 40097826cff0..8df706e7bc6c 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -730,7 +730,7 @@ static bool log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
/* Make sure 64 bit math will not overflow. */
static bool vhost_overflow(u64 uaddr, u64 size)
{
- if (uaddr > ULONG_MAX || size > ULONG_MAX)
+ if (uaddr == ULONG_MAX || size == ULONG_MAX)
return true;
if (!size)
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v1] drivers/vhost/vhost: fix overflow checks in vhost_overflow
2022-12-07 13:46 [PATCH v1] drivers/vhost/vhost: fix overflow checks in vhost_overflow Daniil Tatianin
@ 2022-12-07 15:01 ` Michael S. Tsirkin
2022-12-08 7:21 ` Daniil Tatianin
0 siblings, 1 reply; 3+ messages in thread
From: Michael S. Tsirkin @ 2022-12-07 15:01 UTC (permalink / raw)
To: Daniil Tatianin; +Cc: Jason Wang, kvm, virtualization, netdev, linux-kernel
On Wed, Dec 07, 2022 at 04:46:31PM +0300, Daniil Tatianin wrote:
> The if statement would erroneously check for > ULONG_MAX, which could
> never evaluate to true. Check for equality instead.
>
> Found by Linux Verification Center (linuxtesting.org) with the SVACE
> static analysis tool.
>
> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
It can trigger on a 32 bit system. I'd also expect more analysis
of the code flow than "this can not trigger switch to a condition
that can" to accompany a patch.
> ---
> drivers/vhost/vhost.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 40097826cff0..8df706e7bc6c 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -730,7 +730,7 @@ static bool log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
> /* Make sure 64 bit math will not overflow. */
> static bool vhost_overflow(u64 uaddr, u64 size)
> {
> - if (uaddr > ULONG_MAX || size > ULONG_MAX)
> + if (uaddr == ULONG_MAX || size == ULONG_MAX)
> return true;
>
> if (!size)
> --
> 2.25.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v1] drivers/vhost/vhost: fix overflow checks in vhost_overflow
2022-12-07 15:01 ` Michael S. Tsirkin
@ 2022-12-08 7:21 ` Daniil Tatianin
0 siblings, 0 replies; 3+ messages in thread
From: Daniil Tatianin @ 2022-12-08 7:21 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: Jason Wang, kvm, virtualization, netdev, linux-kernel
On 12/7/22 6:01 PM, Michael S. Tsirkin wrote:
> On Wed, Dec 07, 2022 at 04:46:31PM +0300, Daniil Tatianin wrote:
>> The if statement would erroneously check for > ULONG_MAX, which could
>> never evaluate to true. Check for equality instead.
>>
>> Found by Linux Verification Center (linuxtesting.org) with the SVACE
>> static analysis tool.
>>
>> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
>
> It can trigger on a 32 bit system. I'd also expect more analysis
> of the code flow than "this can not trigger switch to a condition
> that can" to accompany a patch.
Oops, my bad. It can trigger on 32 bit indeed. Sorry, completely
overlooked that.
Thanks
>> ---
>> drivers/vhost/vhost.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> index 40097826cff0..8df706e7bc6c 100644
>> --- a/drivers/vhost/vhost.c
>> +++ b/drivers/vhost/vhost.c
>> @@ -730,7 +730,7 @@ static bool log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
>> /* Make sure 64 bit math will not overflow. */
>> static bool vhost_overflow(u64 uaddr, u64 size)
>> {
>> - if (uaddr > ULONG_MAX || size > ULONG_MAX)
>> + if (uaddr == ULONG_MAX || size == ULONG_MAX)
>> return true;
>>
>> if (!size)
>> --
>> 2.25.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-12-07 13:46 [PATCH v1] drivers/vhost/vhost: fix overflow checks in vhost_overflow Daniil Tatianin
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2022-12-08 7:21 ` Daniil Tatianin
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