On Thu, 25 Feb 2021 10:25:16 -0500 Steven Sistare <steven.sistare@xxxxxxxxxx> wrote: > On 2/24/2021 5:55 PM, Alex Williamson wrote: > > 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, > > Changing size to u64 and using U64_MAX as the upper bound should do the trick: Seems reasonable. Want to slap a title, log, and sign-off on that? Thanks, Alex > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 6cf1dad..b1be0a6 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -181,7 +181,7 @@ static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu, > } > > static struct rb_node *vfio_find_dma_first_node(struct vfio_iommu *iommu, > - dma_addr_t start, size_t size) > + dma_addr_t start, u64 size) > { > struct rb_node *res = NULL; > struct rb_node *node = iommu->dma_list.rb_node; > @@ -1184,7 +1184,7 @@ 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; > + u64 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; > @@ -1200,14 +1200,12 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > if (unmap_all) { > if (iova || size) > goto unlock; > - size = SIZE_MAX; > - } else if (!size || size & (pgsize - 1)) { > + size = U64_MAX; > + } else if (!size || size & (pgsize - 1) || > + iova + size - 1 < iova || size > SIZE_MAX) { > goto unlock; > } > > - if (iova + size - 1 < iova || size > SIZE_MAX) > - goto unlock; > - > /* When dirty tracking is enabled, allow only min supported pgsize */ > if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) && > (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) { >
