[PATCH V2] Fix handling of parse errors in sysfs

[PATCH V2] Fix handling of parse errors in sysfs

[Eric B Munson]

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.

Reported-by: CAI Qian <caiqian@redhat.com>

Signed-off-by: Eric B Munson <emunson@mgebm.net>
Cc: stable@kernel.org
---
Changes from V1
 Reword leader to show problem that is fixed by the patch
 Add stable@kernel.org as a CC to handle stable submission the right way

 mm/hugetlb.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

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;
-- 
1.7.1

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

[Andrew Morton]

On Wed,  5 Jan 2011 13:16:33 -0700
Eric B Munson <emunson@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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