Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> 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
[<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 4365:
 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
 mmap_region+0x138/0xc78 mm/mmap.c:1616
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2122 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

Freed by task 4365:
 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+0x6b0/0xff8 mm/mmap.c:890
 vma_merge+0x880/0xa40 mm/mmap.c:1135
 mmap_region+0x1f4/0xc78 mm/mmap.c:1633
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2122 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff800031a03e88
 which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
The buggy address is located 8 bytes inside of
 184-byte region [ffff800031a03e88, ffff800031a03f40)
The buggy address belongs to the page:
page:ffff7e0000c680c0 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000100100010
raw: dead000000000100 dead000000000200 ffff80005228d000 ffff800052540000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff800052540000

Memory state around the buggy address:
 ffff800031a03d80: fc fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff800031a03e00: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff800031a03e80: fc fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff800031a03f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff800031a03f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================