Re: [stable] [PATCH V2] Fix handling of parse errors in sysfs

[Andrew Morton]

On Wed,  5 Jan 2011 13:16:33 -0700
Eric B Munson <emun...@mgebm.net> wrote:

> When parsing changes to the huge page pool sizes made from userspace
> via the sysfs interface, bogus input values are being covered up
> by nr_hugepages_store_common and nr_overcommit_hugepages_store
> returning 0 when strict_strtoul returns an error.  This can cause an
> infinite loop in the nr_hugepages_store code.  This patch changes
> the return value for these functions to -EINVAL when strict_strtoul
> returns an error.
> 

ah, OK, there we are.

> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 8585524..5cb71a9 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1440,7 +1440,7 @@ static ssize_t nr_hugepages_store_common(bool 
> obey_mempolicy,
>  
>       err = strict_strtoul(buf, 10, &count);
>       if (err)
> -             return 0;
> +             return -EINVAL;
>  
>       h = kobj_to_hstate(kobj, &nid);
>       if (nid == NUMA_NO_NODE) {
> @@ -1519,7 +1519,7 @@ static ssize_t nr_overcommit_hugepages_store(struct 
> kobject *kobj,
>  
>       err = strict_strtoul(buf, 10, &input);
>       if (err)
> -             return 0;
> +             return -EINVAL;
>  
>       spin_lock(&hugetlb_lock);
>       h->nr_overcommit_huge_pages = input;

strict_strtoul() returns an errno - thise code should propagate it, not
overwrite it.

Here's what I ended up with:


diff -puN mm/hugetlb.c~fix-handling-of-parse-errors-in-sysfs mm/hugetlb.c
--- a/mm/hugetlb.c~fix-handling-of-parse-errors-in-sysfs
+++ a/mm/hugetlb.c
@@ -1375,10 +1375,8 @@ static ssize_t nr_hugepages_store_common
        NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
 
        err = strict_strtoul(buf, 10, &count);
-       if (err) {
-               err = 0;                /* This seems wrong */
+       if (err)
                goto out;
-       }
 
        h = kobj_to_hstate(kobj, &nid);
        if (h->order >= MAX_ORDER) {
@@ -1468,7 +1466,7 @@ static ssize_t nr_overcommit_hugepages_s
 
        err = strict_strtoul(buf, 10, &input);
        if (err)
-               return 0;
+               return err;
 
        spin_lock(&hugetlb_lock);
        h->nr_overcommit_huge_pages = input;
_

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