On 11/27/18 4:08 PM, Stefano Stabellini wrote: > On Tue, 27 Nov 2018, Boris Ostrovsky wrote: >> On 11/27/18 3:37 PM, Stefano Stabellini wrote: >>> On Tue, 27 Nov 2018, PanBian wrote: >>>> On Mon, Nov 26, 2018 at 03:31:39PM -0500, Boris Ostrovsky wrote: >>>>> On 11/21/18 9:07 PM, Pan Bian wrote: >>>>>> kfree() is incorrectly used to release the pages allocated by >>>>>> __get_free_page() and __get_free_pages(). Use the matching deallocators >>>>>> i.e., free_page() and free_pages(), respectively. >>>>>> >>>>>> Signed-off-by: Pan Bian <bianpan2...@163.com> >>>>>> --- >>>>>> drivers/xen/pvcalls-front.c | 4 ++-- >>>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c >>>>>> index 2f11ca7..77224d8 100644 >>>>>> --- a/drivers/xen/pvcalls-front.c >>>>>> +++ b/drivers/xen/pvcalls-front.c >>>>>> @@ -385,8 +385,8 @@ static int create_active(struct sock_mapping *map, >>>>>> int *evtchn) >>>>>> out_error: >>>>>> if (*evtchn >= 0) >>>>>> xenbus_free_evtchn(pvcalls_front_dev, *evtchn); >>>>>> - kfree(map->active.data.in); >>>>>> - kfree(map->active.ring); >>>>>> + free_pages((unsigned long)map->active.data.in, >>>>>> PVCALLS_RING_ORDER); >>>>> Is map->active.data.in guaranteed to be NULL when entering this routine? >>>> I am not sure yet. Sorry for that. I observed the mismatches between >>>> __get_free_page and kfree, and submitted the patch. >>>> >>>> But I think your consideration is reasonable. A better solution is to >>>> directly free bytes, a local variable that holds __get_free_pages return >>>> value. If you agree, I will rewrite the patch. >>> Like Boris said, map->active.ring and map->active.data.in are not >>> guaranteed to be NULL or != NULL here. For instance,map->active.ring can >>> be != NULL and map->active.data.in can be NULL. However, free_pages and >>> free_page should be able to cope with it, the same way that kfree is >>> able to cope with it? >> If map->active.data.in can be non-NULL on entry to this routine then I >> think this has been a problem all along. Pan's suggestion to use bytes >> for freeing is going to solve this (assuming bytes will be initialized >> to NULL). > Why is it a problem? map->active.data.in and map->active.ring are only > != NULL if they need to be freed. Otherwise, they are NULL.
That was my question --- I wasn't sure about it, and I read your previous message as if it was possible to be calling create_active() with map->active.data.in pointing somewhere non-NULL. If it is NULL *upon entry* to calling_create() then Pan's original patch is fine. -boris > All structs > are always initialized to zero. I don't think there are any issues. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
