* [RFC] nodemask: Consider MAX_NUMNODES inside node_isset
@ 2017-01-03 8:27 Anshuman Khandual
2017-01-03 8:44 ` Michal Hocko
0 siblings, 1 reply; 5+ messages in thread
From: Anshuman Khandual @ 2017-01-03 8:27 UTC (permalink / raw)
To: linux-kernel, linux-mm; +Cc: mhocko, vbabka, akpm
node_isset can give incorrect result if the node number is beyond the
bitmask size (MAX_NUMNODES in this case) which is not checked inside
test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the
node_isset function before calling test_bit.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
include/linux/nodemask.h | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index 6e66cfd..0aee588b 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -139,7 +139,13 @@ static inline void __nodes_clear(nodemask_t *dstp, unsigned int nbits)
}
/* No static inline type checking - see Subtlety (1) above. */
-#define node_isset(node, nodemask) test_bit((node), (nodemask).bits)
+#define node_isset(node, nodemask) node_test_bit(node, nodemask, MAX_NUMNODES)
+static inline int node_test_bit(int node, nodemask_t nodemask, int maxnodes)
+{
+ if (node >= maxnodes)
+ return 0;
+ return test_bit((node), (nodemask).bits);
+}
#define node_test_and_set(node, nodemask) \
__node_test_and_set((node), &(nodemask))
--
1.8.3.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [RFC] nodemask: Consider MAX_NUMNODES inside node_isset
2017-01-03 8:27 [RFC] nodemask: Consider MAX_NUMNODES inside node_isset Anshuman Khandual
@ 2017-01-03 8:44 ` Michal Hocko
2017-01-03 9:07 ` Anshuman Khandual
0 siblings, 1 reply; 5+ messages in thread
From: Michal Hocko @ 2017-01-03 8:44 UTC (permalink / raw)
To: Anshuman Khandual; +Cc: linux-kernel, linux-mm, vbabka, akpm
On Tue 03-01-17 13:57:53, Anshuman Khandual wrote:
> node_isset can give incorrect result if the node number is beyond the
> bitmask size (MAX_NUMNODES in this case) which is not checked inside
> test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the
> node_isset function before calling test_bit.
Could you be more specific when such a thing might happen? Have you seen
any in-kernel user who would give such a bogus node?
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> include/linux/nodemask.h | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> index 6e66cfd..0aee588b 100644
> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -139,7 +139,13 @@ static inline void __nodes_clear(nodemask_t *dstp, unsigned int nbits)
> }
>
> /* No static inline type checking - see Subtlety (1) above. */
> -#define node_isset(node, nodemask) test_bit((node), (nodemask).bits)
> +#define node_isset(node, nodemask) node_test_bit(node, nodemask, MAX_NUMNODES)
> +static inline int node_test_bit(int node, nodemask_t nodemask, int maxnodes)
> +{
> + if (node >= maxnodes)
> + return 0;
> + return test_bit((node), (nodemask).bits);
> +}
>
> #define node_test_and_set(node, nodemask) \
> __node_test_and_set((node), &(nodemask))
> --
> 1.8.3.1
>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC] nodemask: Consider MAX_NUMNODES inside node_isset
2017-01-03 8:44 ` Michal Hocko
@ 2017-01-03 9:07 ` Anshuman Khandual
2017-01-03 9:17 ` Michal Hocko
0 siblings, 1 reply; 5+ messages in thread
From: Anshuman Khandual @ 2017-01-03 9:07 UTC (permalink / raw)
To: Michal Hocko, Anshuman Khandual; +Cc: linux-kernel, linux-mm, vbabka, akpm
On 01/03/2017 02:14 PM, Michal Hocko wrote:
> On Tue 03-01-17 13:57:53, Anshuman Khandual wrote:
>> node_isset can give incorrect result if the node number is beyond the
>> bitmask size (MAX_NUMNODES in this case) which is not checked inside
>> test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the
>> node_isset function before calling test_bit.
> Could you be more specific when such a thing might happen? Have you seen
> any in-kernel user who would give such a bogus node?
Have not seen this through any in-kernel use case. While rebasing the CDM
zonelist rebuilding series, I came across this through an error path when
a bogus node value of 256 (MAX_NUMNODES on POWER) is received when we call
first_node() on an empty nodemask (which itself seems weird as well).
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC] nodemask: Consider MAX_NUMNODES inside node_isset
2017-01-03 9:07 ` Anshuman Khandual
@ 2017-01-03 9:17 ` Michal Hocko
2017-01-03 9:47 ` Anshuman Khandual
0 siblings, 1 reply; 5+ messages in thread
From: Michal Hocko @ 2017-01-03 9:17 UTC (permalink / raw)
To: Anshuman Khandual; +Cc: linux-kernel, linux-mm, vbabka, akpm
On Tue 03-01-17 14:37:09, Anshuman Khandual wrote:
> On 01/03/2017 02:14 PM, Michal Hocko wrote:
> > On Tue 03-01-17 13:57:53, Anshuman Khandual wrote:
> >> node_isset can give incorrect result if the node number is beyond the
> >> bitmask size (MAX_NUMNODES in this case) which is not checked inside
> >> test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the
> >> node_isset function before calling test_bit.
> > Could you be more specific when such a thing might happen? Have you seen
> > any in-kernel user who would give such a bogus node?
>
> Have not seen this through any in-kernel use case. While rebasing the CDM
> zonelist rebuilding series,
Then fix this particular code path...
> I came across this through an error path when
> a bogus node value of 256 (MAX_NUMNODES on POWER) is received when we call
> first_node() on an empty nodemask (which itself seems weird as well).
Does calling first_node on an empty nodemask make any sense? If there is
a risk then I would expect nodes_empty() check before doing any mask
related operations.
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC] nodemask: Consider MAX_NUMNODES inside node_isset
2017-01-03 9:17 ` Michal Hocko
@ 2017-01-03 9:47 ` Anshuman Khandual
0 siblings, 0 replies; 5+ messages in thread
From: Anshuman Khandual @ 2017-01-03 9:47 UTC (permalink / raw)
To: Michal Hocko, Anshuman Khandual; +Cc: linux-kernel, linux-mm, vbabka, akpm
On 01/03/2017 02:47 PM, Michal Hocko wrote:
> On Tue 03-01-17 14:37:09, Anshuman Khandual wrote:
>> On 01/03/2017 02:14 PM, Michal Hocko wrote:
>>> On Tue 03-01-17 13:57:53, Anshuman Khandual wrote:
>>>> node_isset can give incorrect result if the node number is beyond the
>>>> bitmask size (MAX_NUMNODES in this case) which is not checked inside
>>>> test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the
>>>> node_isset function before calling test_bit.
>>> Could you be more specific when such a thing might happen? Have you seen
>>> any in-kernel user who would give such a bogus node?
>>
>> Have not seen this through any in-kernel use case. While rebasing the CDM
>> zonelist rebuilding series,
>
> Then fix this particular code path...
Yeah I did.
>
>> I came across this through an error path when
>> a bogus node value of 256 (MAX_NUMNODES on POWER) is received when we call
>> first_node() on an empty nodemask (which itself seems weird as well).
>
> Does calling first_node on an empty nodemask make any sense? If there is
> a risk then I would expect nodes_empty() check before doing any mask
> related operations.
Hmm, you are right. All these checks should be done by the caller not
these nodemask helper functions.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2017-01-03 8:27 [RFC] nodemask: Consider MAX_NUMNODES inside node_isset Anshuman Khandual
2017-01-03 8:44 ` Michal Hocko
2017-01-03 9:07 ` Anshuman Khandual
2017-01-03 9:17 ` Michal Hocko
2017-01-03 9:47 ` Anshuman Khandual
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