On 2/25/2021 1:00 PM, Alex Williamson wrote: > On Thu, 25 Feb 2021 10:25:16 -0500 > Steven Sistare wrote: > >> On 2/24/2021 5:55 PM, Alex Williamson wrote: >>> On Tue, 23 Feb 2021 18:58:18 -0500 >>> Steven Sistare 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 wrote: >>>>>> >>>>>>> On 2/23/2021 12:45 PM, Alex Williamson wrote: >>>>>>>> On Tue, 23 Feb 2021 08:56:36 -0500 >>>>>>>> Steven Sistare wrote: >>>>>>>> >>>>>>>>> On 2/22/2021 6:17 PM, Alex Williamson wrote: >>>>>>>>>> On Mon, 22 Feb 2021 15:51:45 -0700 >>>>>>>>>> Alex Williamson wrote: >>>>>>>>>> >>>>>>>>>>> On Mon, 22 Feb 2021 17:10:43 +0300 >>>>>>>>>>> Dan Carpenter 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 >>>>>>>>>>>> Reported-by: Dan Carpenter >>>>>>>>>>>> >>>>>>>>>>>> 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, See attached - Steve