Messages in this thread | | | Subject | Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update | From | Suzuki K Poulose <> | Date | Fri, 10 Mar 2017 18:37:21 +0000 |
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On 10/03/17 15:50, Andrey Konovalov wrote: > On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote: >> Hi, >> >> I've got the following error report while fuzzing the kernel with syzkaller. >> >> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8). >> >> Unfortunately I can't reproduce it. >> >> ================================================================== >> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63 >> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615 >> >> CPU: 1 PID: 26615 Comm: syz-executor Not tainted >> 4.11.0-rc1-next-20170308-xc2-dirty #3 >> Hardware name: Hardkernel ODROID-C2 (DT) >> Call trace: >> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505 >> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228 >> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline] >> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52 >> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250 >> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349 >> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline] >> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393 >> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63 >> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124 >> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488 >> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817 >> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8 >> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026 >> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58 >> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075 >> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region >> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline] >> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308 >> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960 >> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline] >> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685 >> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline] >> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691 >> [<ffff200008083f70>] el0_svc_naked+0x24/0x28 >> >> Allocated by task 26657: >> save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133 >> save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216 >> save_stack mm/kasan/kasan.c:515 [inline] >> set_track mm/kasan/kasan.c:527 [inline] >> kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619 >> kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557 >> slab_post_alloc_hook mm/slab.h:456 [inline] >> slab_alloc_node mm/slub.c:2718 [inline] >> slab_alloc mm/slub.c:2726 [inline] >> kmem_cache_alloc+0x144/0x230 mm/slub.c:2731 >> __split_vma+0x118/0x608 mm/mmap.c:2515 >> do_munmap+0x194/0x9b0 mm/mmap.c:2636 >> Freed by task 26657: >> save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133 >> save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216 >> save_stack mm/kasan/kasan.c:515 [inline] >> set_track mm/kasan/kasan.c:527 [inline] >> kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592 >> slab_free_hook mm/slub.c:1357 [inline] >> slab_free_freelist_hook mm/slub.c:1379 [inline] >> slab_free mm/slub.c:2961 [inline] >> kmem_cache_free+0x80/0x258 mm/slub.c:2983 >> __vma_adjust+0x6b0/0xf mm/mmap.c:890] el0_svc_naked+0x24/0x28 >> >> The buggy address belongs to the object at ffff80003b9a2000 >> which belongs to the cache vm_area_struct(647:session-6.scope) of size 184 >> The buggy address is located 64 bytes inside of >> 184-byte region [ffff80003b9a2000, ffff80003b9a20b8) >> The buggy address belongs to the page: >> page:ffff7e0000ee6880 count:1 mapcount:0 mapping: (null) index:0x0 >> flags: 0xfffc00000000100(slab) >> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010 >> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980 >> page dumped because: kasan: bad access detected >> page->mem_cgroup:ffff80005ac99980 >> >> Memory state around the buggy address: >> ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >> ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb >> ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== > > Another one that looks related and doesn't have parts of stack traces missing: > > ================================================================== > BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114 > Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360 > > CPU: 2 PID: 4360 Comm: syz-executor Not tainted > 4.11.0-rc1-next-20170308-xc2-dirty #3 > Hardware name: Hardkernel ODROID-C2 (DT) > Call trace: > [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505 > [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228 > [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline] > [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52 > [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250 > [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349 > [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline] > [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393 > [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114 > [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488 > arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
It looks like we don't take the mmap_sem before calling find_vma() in stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing the race, with probably the test trying to unmap ranges in between.
Suzuki
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