[PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

[PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

[liuyuntao]

From: Liu Yuntao <liuyuntao10@huawei.com>

When we specify a large number for node in hugepages parameter,
it may be parsed to another number due to truncation in this statement:
	node = tmp;

For example, add following parameter in command line:
	hugepagesz=1G hugepages=4294967297:5
and kernel will allocate 5 hugepages for node 1 instead of ignoring it.

I move the validation check earlier to fix this issue, and slightly
simplifies the condition here.

Fixes: b5389086ad7be0 ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
Signed-off-by: Liu Yuntao <liuyuntao10@huawei.com>
---
 mm/hugetlb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 61895cc01d09..0929547f6ad6 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4159,10 +4159,10 @@ static int __init hugepages_setup(char *s)
 				pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
 				return 0;
 			}
+			if (tmp >= nr_online_nodes)
+				goto invalid;
 			node = tmp;
 			p += count + 1;
-			if (node < 0 || node >= nr_online_nodes)
-				goto invalid;
 			/* Parse hugepages */
 			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
 				goto invalid;
-- 
2.33.0

Re: [PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

[Mike Kravetz]

On 2/9/22 05:40, liuyuntao wrote:
> From: Liu Yuntao <liuyuntao10@huawei.com>
> 
> When we specify a large number for node in hugepages parameter,
> it may be parsed to another number due to truncation in this statement:
> 	node = tmp;
> 
> For example, add following parameter in command line:
> 	hugepagesz=1G hugepages=4294967297:5
> and kernel will allocate 5 hugepages for node 1 instead of ignoring it.
> 
> I move the validation check earlier to fix this issue, and slightly
> simplifies the condition here.
> 
> Fixes: b5389086ad7be0 ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
> Signed-off-by: Liu Yuntao <liuyuntao10@huawei.com>
> ---
>  mm/hugetlb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 61895cc01d09..0929547f6ad6 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4159,10 +4159,10 @@ static int __init hugepages_setup(char *s)
>  				pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
>  				return 0;
>  			}
> +			if (tmp >= nr_online_nodes)
> +				goto invalid;
>  			node = tmp;

I am surprised none of the automated checking complained about that
assignment.

>  			p += count + 1;
> -			if (node < 0 || node >= nr_online_nodes)

I can't remember, but I think that check for node < 0 was added to handle
overflow during the above assignment.  Do you remember Zhenguo Yao?
   
> -				goto invalid;
>  			/* Parse hugepages */
>  			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
>  				goto invalid;

Thanks,

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

-- 
Mike Kravetz

Re: [PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

[liuyuntao]

On 2022-02-10  0:43 UTC, Mike Kravetz wrote:
> On 2/9/22 05:40, liuyuntao wrote:
> > From: Liu Yuntao <liuyuntao10@huawei.com>
> > 
> > When we specify a large number for node in hugepages parameter,
> > it may be parsed to another number due to truncation in this statement:
> > 	node = tmp;
> > 
> > For example, add following parameter in command line:
> > 	hugepagesz=1G hugepages=4294967297:5
> > and kernel will allocate 5 hugepages for node 1 instead of ignoring it.
> > 
> > I move the validation check earlier to fix this issue, and slightly
> > simplifies the condition here.
> > 
> > Fixes: b5389086ad7be0 ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
> > Signed-off-by: Liu Yuntao <liuyuntao10@huawei.com>
> > ---
> >  mm/hugetlb.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 61895cc01d09..0929547f6ad6 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -4159,10 +4159,10 @@ static int __init hugepages_setup(char *s)
> >  				pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
> >  				return 0;
> >  			}
> > +			if (tmp >= nr_online_nodes)
> > +				goto invalid;
> >  			node = tmp;
> 
> I am surprised none of the automated checking complained about that
> assignment.

I think such assignments may be very common in kernel, and thus automated
checks just ignore them.

> 
> >  			p += count + 1;
> > -			if (node < 0 || node >= nr_online_nodes)
> 
> I can't remember, but I think that check for node < 0 was added to handle
> overflow during the above assignment.  Do you remember Zhenguo Yao?

No, I don't. I took a look and found that the check for node < 0 has been
there since his first version of patch.

>    
> > -				goto invalid;
> >  			/* Parse hugepages */
> >  			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
> >  				goto invalid;
> 
> Thanks,
> 
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> 
> -- 
> Mike Kravetz

--
Liu Yuntao

Re: [PATCH] hugetlbfs: fix a truncation issue in hugepages parameter

[Zhenguo Yao]

Mike Kravetz <mike.kravetz@oracle.com> 于2022年2月10日周四 08:44写道：
>
> On 2/9/22 05:40, liuyuntao wrote:
> > From: Liu Yuntao <liuyuntao10@huawei.com>
> >
> > When we specify a large number for node in hugepages parameter,
> > it may be parsed to another number due to truncation in this statement:
> >       node = tmp;
> >
> > For example, add following parameter in command line:
> >       hugepagesz=1G hugepages=4294967297:5
> > and kernel will allocate 5 hugepages for node 1 instead of ignoring it.
> >
> > I move the validation check earlier to fix this issue, and slightly
> > simplifies the condition here.
> >
> > Fixes: b5389086ad7be0 ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
> > Signed-off-by: Liu Yuntao <liuyuntao10@huawei.com>
> > ---
> >  mm/hugetlb.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 61895cc01d09..0929547f6ad6 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -4159,10 +4159,10 @@ static int __init hugepages_setup(char *s)
> >                               pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
> >                               return 0;
> >                       }
> > +                     if (tmp >= nr_online_nodes)
> > +                             goto invalid;
> >                       node = tmp;
>
> I am surprised none of the automated checking complained about that
> assignment.
>
> >                       p += count + 1;
> > -                     if (node < 0 || node >= nr_online_nodes)
>
> I can't remember, but I think that check for node < 0 was added to handle
> overflow during the above assignment.  Do you remember Zhenguo Yao?
>
Sorry for my late reply.  This check for node < 0 was added
to handle node parameter overflow from the earliest version:
https://lore.kernel.org/lkml/20210820030536.25737-1-yaozhenguo1@gmail.com/
Parameter of node allocation was:  hugepages_node=xx hugepages=xx at this
version. With the changing of the code, this check has lost its effect.

> > -                             goto invalid;
> >                       /* Parse hugepages */
> >                       if (sscanf(p, "%lu%n", &tmp, &count) != 1)
> >                               goto invalid;
>
> Thanks,
>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> --
> Mike Kravetz