[PATCH 1/2] hugetlb, sysctl: pass '.extra1 = NULL' rather then '.extra1 = &zero'

[PATCH 1/2] hugetlb, sysctl: pass '.extra1 = NULL' rather then '.extra1 = &zero'

[Andrey Ryabinin]

Commit ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity") replaced
'unsigned long hugetlb_zero' with 'int zero' leading to out-of-bounds access
in proc_doulongvec_minmax().
Use '.extra1 = NULL' instead of '.extra1 = &zero'. Passing NULL is equivalent to
passing minimal value, which is 0 for unsigned types.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Suggested-by: Manfred Spraul <manfred@colorfullife.com>
Fixes: ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity")
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
---
 kernel/sysctl.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 137c7f6..88ea2d6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1248,7 +1248,6 @@ static struct ctl_table vm_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= hugetlb_sysctl_handler,
-		.extra1		= &zero,
 	},
 #ifdef CONFIG_NUMA
 	{
@@ -1257,7 +1256,6 @@ static struct ctl_table vm_table[] = {
 		.maxlen         = sizeof(unsigned long),
 		.mode           = 0644,
 		.proc_handler   = &hugetlb_mempolicy_sysctl_handler,
-		.extra1		= &zero,
 	},
 #endif
 	 {
@@ -1280,7 +1278,6 @@ static struct ctl_table vm_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= hugetlb_overcommit_handler,
-		.extra1		= &zero,
 	},
 #endif
 	{
-- 
2.2.0

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[PATCH 2/2] mm: hugetlb: fix type of hugetlb_treat_as_movable variable

[Andrey Ryabinin]

hugetlb_treat_as_movable declared as unsigned long, but
proc_dointvec() used for parsing it:

static struct ctl_table vm_table[] = {
...
	{
		.procname	= "hugepages_treat_as_movable",
		.data		= &hugepages_treat_as_movable,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},

This seems harmless, but it's better to use int type here.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
---
 include/linux/hugetlb.h | 2 +-
 mm/hugetlb.c            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 431b7fc..7d78563 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -86,7 +86,7 @@ void free_huge_page(struct page *page);
 pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud);
 #endif
 
-extern unsigned long hugepages_treat_as_movable;
+extern int hugepages_treat_as_movable;
 extern int sysctl_hugetlb_shm_group;
 extern struct list_head huge_boot_pages;
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 85032de..be0e5d0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -35,7 +35,7 @@
 #include <linux/node.h>
 #include "internal.h"
 
-unsigned long hugepages_treat_as_movable;
+int hugepages_treat_as_movable;
 
 int hugetlb_max_hstate __read_mostly;
 unsigned int default_hstate_idx;
-- 
2.2.0

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Re: [PATCH 2/2] mm: hugetlb: fix type of hugetlb_treat_as_movable variable

[David Rientjes]

On Wed, 17 Dec 2014, Andrey Ryabinin wrote:

> hugetlb_treat_as_movable declared as unsigned long, but
> proc_dointvec() used for parsing it:
> 
> static struct ctl_table vm_table[] = {
> ...
> 	{
> 		.procname	= "hugepages_treat_as_movable",
> 		.data		= &hugepages_treat_as_movable,
> 		.maxlen		= sizeof(int),
> 		.mode		= 0644,
> 		.proc_handler	= proc_dointvec,
> 	},
> 
> This seems harmless, but it's better to use int type here.
> 
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>

Acked-by: David Rientjes <rientjes@google.com>

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Re: [PATCH 1/2] hugetlb, sysctl: pass '.extra1 = NULL' rather then '.extra1 = &zero'

[David Rientjes]

On Wed, 17 Dec 2014, Andrey Ryabinin wrote:

> Commit ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity") replaced
> 'unsigned long hugetlb_zero' with 'int zero' leading to out-of-bounds access
> in proc_doulongvec_minmax().
> Use '.extra1 = NULL' instead of '.extra1 = &zero'. Passing NULL is equivalent to
> passing minimal value, which is 0 for unsigned types.
> 
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Suggested-by: Manfred Spraul <manfred@colorfullife.com>
> Fixes: ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity")
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>

Acked-by: David Rientjes <rientjes@google.com>

Patch title is a little awkward, though, maybe "mm, hugetlb: remove 
unnecessary lower bound on sysctl handlers"?

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