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. 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