Messages in this thread | | | Date | Sat, 15 Dec 2012 18:12:11 +0000 | From | Al Viro <> | Subject | oopsable race in xen-gntdev (unsafe vma access) |
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1) find_vma() is *not* safe without ->mmap_sem and its result may very well be freed just as it's returned to caller. IOW, gntdev_ioctl_get_offset_for_vaddr() is racy and may end up with dereferencing freed memory.
2) gntdev_vma_close() is putting NULL into map->vma with only ->mmap_sem held by caller. Things like if (!map->vma) continue; if (map->vma->vm_start >= end) continue; if (map->vma->vm_end <= start) done with just priv->lock held are racy.
I'm not familiar with the code, but it looks like we need to protect gntdev_vma_close() guts with the same spinlock and probably hold ->mmap_sem shared around the "find_vma()+get to map->{index,count}" in the ioctl. Or replace the logics in ioctl with search through the list of grant_map under the same spinlock...
Comments?
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