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 unmap-all logic only looks for a first entry to unmap in the [0..SIZE_MAX] range. If an entry happens to exist there, we'll unmap everything, but the user would have no requirement to have a mapping within that range, their first mapping could exist at iova = (SIZE_MAX + 1). So unmap-all would effectively need a special case to use rb_first(), which mostly negates the reason we added vfio_find_dma_first_node(). Right? Thanks, Alex > >> For unmap, these fixes should suffice, and I would rather do this than > >> disable the unmap-all flag for a corner case: > >> > >> vfio_dma_do_unmap() > >> size_t unmapped = 0; > >> unsigned long size = unmap->size; > >> ==> > >> u64 unmapped = 0; > >> u64 size = unmap->size; > >> > >> static struct rb_node *vfio_find_dma_first_node( > >> struct vfio_iommu *iommu, dma_addr_t start, size_t size) > >> ==> > >> static struct rb_node *vfio_find_dma_first_node( > >> struct vfio_iommu *iommu, dma_addr_t start, u64 size) > >> > >> And maybe use dma_addr_t instead of u64 in the above (which is 64 bits for > >> CONFIG_X86_PAE). > >> > >> However, there are other places in the existing code that need tweaking > >> to be safe for PAE, the vfio_find_dma() size arg for one. > > > > Yes, it looks like the IOMMU aperture checking using vfio_find_dma() > > could have issues where dma_addr_t > size_t. Do you want to propose a > > patch? Thanks, > > > > Alex > > > >>> I can't say I'm > >>> really interested in adding complexity to make it work in such a case > >>> either. Maybe we can just not expose it, ex: > >>> > >>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >>> index ed03f3fcb07e..6b69a74b3db0 100644 > >>> --- a/drivers/vfio/vfio_iommu_type1.c > >>> +++ b/drivers/vfio/vfio_iommu_type1.c > >>> @@ -1207,7 +1207,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>> int ret = -EINVAL, retries = 0; > >>> unsigned long pgshift; > >>> dma_addr_t iova = unmap->iova; > >>> - unsigned long size = unmap->size; > >>> + size_t size = unmap->size; > >>> bool unmap_all = unmap->flags & VFIO_DMA_UNMAP_FLAG_ALL; > >>> bool invalidate_vaddr = unmap->flags & VFIO_DMA_UNMAP_FLAG_VADDR; > >>> struct rb_node *n, *first_n; > >>> @@ -1228,7 +1228,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >>> goto unlock; > >>> } > >>> > >>> - if (iova + size - 1 < iova || size > SIZE_MAX) > >>> + if (iova + size - 1 < iova || unmap->size > SIZE_MAX) > >>> goto unlock; > >>> > >>> /* When dirty tracking is enabled, allow only min supported pgsize */ > >>> @@ -2657,9 +2657,10 @@ static int vfio_iommu_type1_check_extension(struct vfio_iommu *iommu, > >>> case VFIO_TYPE1_IOMMU: > >>> case VFIO_TYPE1v2_IOMMU: > >>> case VFIO_TYPE1_NESTING_IOMMU: > >>> - case VFIO_UNMAP_ALL: > >>> case VFIO_UPDATE_VADDR: > >>> return 1; > >>> + case VFIO_UNMAP_ALL: > >>> + return PHYS_ADDR_MAX == SIZE_MAX ? 1 : 0; > >>> case VFIO_DMA_CC_IOMMU: > >>> if (!iommu) > >>> return 0; > >>> @@ -2868,6 +2869,10 @@ static int vfio_iommu_type1_unmap_dma(struct vfio_iommu *iommu, > >>> VFIO_DMA_UNMAP_FLAG_VADDR))) > >>> return -EINVAL; > >>> > >>> + if ((PHYS_ADDR_MAX != SIZE_MAX) && > >>> + (unmap.flags & VFIO_DMA_UNMAP_FLAG_ALL)) > >>> + return -EINVAL; > >>> + > >>> if (unmap.flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) { > >>> unsigned long pgshift; > >>> > >>> > >>> > >>> > >>> > >>>>> Is the " - 1" intentional on the other overflow check? As in it's okay > >>>>> to wrap around to zero but not further than that? Sometimes this is > >>>>> intentional but it requires more subsystem expertise than I possess. > >>>> > >>>> Yes, since we're dealing with a start + length we need to account for > >>>> the -1 in the end value, otherwise the user could never unmap the last > >>>> page of the address space. Thanks for the report! > >>>> > >>>> Alex > >>>> > >>>>> cade075f265b25 Kirti Wankhede 2020-05-29 1094 goto unlock; > >>>>> 73fa0d10d077d9 Alex Williamson 2012-07-31 1095 > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1096 /* When dirty tracking is enabled, allow only min supported pgsize */ > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1097 if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1098 (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) { > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1099 goto unlock; > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1100 } > >>>>> 73fa0d10d077d9 Alex Williamson 2012-07-31 1101 > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1102 WARN_ON((pgsize - 1) & PAGE_MASK); > >>>>> 331e33d2960c82 Kirti Wankhede 2020-05-29 1103 again: > >>>>> 1ef3e2bc04223f Alex Williamson 2014-02-26 1104 /* > >>>>> > >>>>> --- > >>>>> 0-DAY CI Kernel Test Service, Intel Corporation > >>>>> https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx > >>>> > >>> > >> > > >
