On Tue, 23 Feb 2021 18:58:18 -0500 Steven Sistare <steven.sistare@xxxxxxxxxx> wrote: > On 2/23/2021 4:52 PM, Steven Sistare wrote: > > On 2/23/2021 4:10 PM, Alex Williamson wrote: > >> On Tue, 23 Feb 2021 15:37:31 -0500 > >> Steven Sistare <steven.sistare@xxxxxxxxxx> wrote: > >> > >>> On 2/23/2021 12:45 PM, Alex Williamson wrote: > >>>> On Tue, 23 Feb 2021 08:56:36 -0500 > >>>> Steven Sistare <steven.sistare@xxxxxxxxxx> wrote: > >>>> > >>>>> On 2/22/2021 6:17 PM, Alex Williamson wrote: > >>>>>> On Mon, 22 Feb 2021 15:51:45 -0700 > >>>>>> Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > >>>>>> > >>>>>>> On Mon, 22 Feb 2021 17:10:43 +0300 > >>>>>>> Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote: > >>>>>>> > >>>>>>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > >>>>>>>> head: 37dfbfbdca66834bc0f64ec9b35e09ac6c8898da > >>>>>>>> commit: 0f53afa12baec8c00f5d1d6afb49325ada105253 [6931/12022] vfio/type1: unmap cleanup > >>>>>>> > >>>>>>> It's always the patches that claim no functional change... ;) > >>>>>>> > >>>>>>>> config: i386-randconfig-m021-20210222 (attached as .config) > >>>>>>>> compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 > >>>>>>>> > >>>>>>>> If you fix the issue, kindly add following tag as appropriate > >>>>>>>> Reported-by: kernel test robot <lkp@xxxxxxxxx> > >>>>>>>> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > >>>>>>>> > >>>>>>>> New smatch warnings: > >>>>>>>> drivers/vfio/vfio_iommu_type1.c:1093 vfio_dma_do_unmap() warn: impossible condition '(size > (~0)) => (0-u32max > u32max)' > >>>>>>>> > >>>>>>>> vim +1093 drivers/vfio/vfio_iommu_type1.c > >>>>>>>> > >>>>>>>> 73fa0d10d077d9 Alex Williamson 2012-07-31 1071 static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>>>>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1072 struct vfio_iommu_type1_dma_unmap *unmap, > >>>>>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1073 struct vfio_bitmap *bitmap) > >>>>>>>> 73fa0d10d077d9 Alex Williamson 2012-07-31 1074 { > >>>>>>>> c086de818dd81c Kirti Wankhede 2016-11-17 1075 struct vfio_dma *dma, *dma_last = NULL; > >>>>>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1076 size_t unmapped = 0, pgsize; > >>>>>>>> 0f53afa12baec8 Steve Sistare 2021-01-29 1077 int ret = -EINVAL, retries = 0; > >>>>>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1078 unsigned long pgshift; > >>>>>>>> 0f53afa12baec8 Steve Sistare 2021-01-29 1079 dma_addr_t iova = unmap->iova; > >>>>>>>> 0f53afa12baec8 Steve Sistare 2021-01-29 1080 unsigned long size = unmap->size; > >>>>>>>> ^^^^^^^^^^^^^^^^^^ > >>>>>>>> > >>>>>>>> 73fa0d10d077d9 Alex Williamson 2012-07-31 1081 > >>>>>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1082 mutex_lock(&iommu->lock); > >>>>>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1083 > >>>>>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1084 pgshift = __ffs(iommu->pgsize_bitmap); > >>>>>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1085 pgsize = (size_t)1 << pgshift; > >>>>>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1086 > >>>>>>>> 0f53afa12baec8 Steve Sistare 2021-01-29 1087 if (iova & (pgsize - 1)) > >>>>>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1088 goto unlock; > >>>>>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1089 > >>>>>>>> 0f53afa12baec8 Steve Sistare 2021-01-29 1090 if (!size || size & (pgsize - 1)) > >>>>>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1091 goto unlock; > >>>>>>>> 73fa0d10d077d9 Alex Williamson 2012-07-31 1092 > >>>>>>>> 0f53afa12baec8 Steve Sistare 2021-01-29 @1093 if (iova + size - 1 < iova || size > SIZE_MAX) > >>>>>>>> > >>>>>>>> size is unsigned long and SIZE_MAX is ULONG_MAX so "size > SIZE_MAX" > >>>>>>>> does not make sense. > >>>>>>> > >>>>>>> I think it made sense before the above commit, where unmap->size is a > >>>>>>> __u64 and a user could provide a value that exceeds SIZE_MAX on ILP32. > >>>>>>> Seems like the fix is probably to use a size_t for the local variable > >>>>>>> and restore this test to compare (unmap->size > SIZE_MAX). Steve? > >>>>>> > >>>>>> Actually it seems like VFIO_DMA_UNMAP_FLAG_ALL doesn't work when > >>>>>> PHYS_ADDR_MAX != SIZE_MAX (ex. x86 PAE - I think). > >>>>> > >>>>> It seems like PAE causes problems even before VFIO_DMA_UNMAP_FLAG_ALL. > >>>> > >>>> This wouldn't surprise me, I don't know of any actual non-64bit users > >>>> and pure 32bit support was only lightly validated ages ago. > >>>> > >>>>> In the previous vfio_dma_do_unmap code, the u64 unmap->size would be > >>>>> truncated when passed to vfio_find_dma. > >>>> > >>>> We would have failed with -EINVAL before we get there due to this > >>>> SIZE_MAX test. I think the existing (previous) PAE interface is at > >>>> least self consistent; I see the mapping path also attempts to check > >>>> that casting map->size as size_t still matches the original value. > >>> > >>> Good point, and it also checks for vaddr and iova overflow and wrap: > >>> > >>> vfio_dma_do_map() > >>> if (map->size != size || map->vaddr != vaddr || map->iova != iova) > >>> return -EINVAL; > >>> if (iova + size - 1 < iova || vaddr + size - 1 < vaddr) { > >>> ret = -EINVAL; > >>> > >>> With that, I don't see a problem with PAE, for unmap-all or otherwise. > >>> We just need "u64 size" in vfio_dma_do_unmap to avoid the smatch warning. > >> > >> I'm not convinced. My understanding is that on PAE phys_addr_t is > >> 64-bit while size_t is 32-bit. dma_addr_t (iova above) seems to follow > >> phys_addr_t. That suggests to me that our {un}map.iova lives in a > >> 64-bit address space, but each mapping is limited to 32-bits. The > > > > OK, the "map->iova != iova" test does not help because dma_addr_t is 64-bit. My bad. > > So, I re-propose my fix for unmap-all from previous email. > > > > I am not keen on proposing a fix for the potential legacy bugs, vfio_find_dma() and > > its callers, if no one is reporting bugs and no one uses it with vfio. It has the > > potential for regression with no upside. > > ... but there are no legacy bugs because size is constrained to 32-bits in do_map as > you pointed out, so all calls to vfio_find_dma are safe. Right, all legacy call paths are ok afaict, but the unmap-all flag can't reach any mappings if there are none below an iova of SIZE_MAX. We should either fix vfio_find_first_dma_node() for this scenario or disable unmap-all where this is a possibility. Thanks, Alex
