Re: KASAN: slab-out-of-bounds Read in handle_vmptrld

[Will Deacon]

On Wed, Sep 11, 2019 at 01:38:08PM -0700, syzbot wrote:
> syzbot found the following crash on:
> 
> HEAD commit:    1e3778cb Merge tag 'scsi-fixes' of git://git.kernel.org/pu..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15bdfc5e600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b89bb446a3faaba4
> dashboard link: https://syzkaller.appspot.com/bug?extid=46f1dd7dbbe2bfb98b10
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1709421a600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=168fc4b2600000
> 
> The bug was bisected to:
> 
> commit a87f854ddcf7ff7e044d72db0aa6da82f26d69a6
> Author: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Date:   Wed Oct 11 15:39:40 2017 +0000
> 
>     ARM64: dts: meson-gx: remove unnecessary uart compatible
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17e78a6e600000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=14178a6e600000
> console output: https://syzkaller.appspot.com/x/log.txt?x=10178a6e600000

Unfortunately, I think the bisect must be bogus, since I can't see how a
devicetree change for an arm64 file can affect the x86 KVM instruction
emulation.

Maybe somebody from the x86 KVM side could have a look at the KASAN splat?

Will

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+46f1dd7dbbe2bfb98b10@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: a87f854ddcf7 ("ARM64: dts: meson-gx: remove unnecessary uart
> compatible")
> 
> L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and
> https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for
> details.
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in handle_vmptrld
> arch/x86/kvm/vmx/nested.c:4789 [inline]
> BUG: KASAN: slab-out-of-bounds in handle_vmptrld+0x777/0x800
> arch/x86/kvm/vmx/nested.c:4749
> Read of size 4 at addr ffff888091e10000 by task syz-executor758/10006
> 
> CPU: 1 PID: 10006 Comm: syz-executor758 Not tainted 5.3.0-rc7+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
>  print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
>  __kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
>  kasan_report+0x12/0x17 mm/kasan/common.c:618
>  __asan_report_load_n_noabort+0xf/0x20 mm/kasan/generic_report.c:142
>  handle_vmptrld arch/x86/kvm/vmx/nested.c:4789 [inline]
>  handle_vmptrld+0x777/0x800 arch/x86/kvm/vmx/nested.c:4749
>  vmx_handle_exit+0x299/0x15e0 arch/x86/kvm/vmx/vmx.c:5886
>  vcpu_enter_guest+0x1087/0x5e90 arch/x86/kvm/x86.c:8088
>  vcpu_run arch/x86/kvm/x86.c:8152 [inline]
>  kvm_arch_vcpu_ioctl_run+0x464/0x1750 arch/x86/kvm/x86.c:8360
>  kvm_vcpu_ioctl+0x4dc/0xfd0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2765
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  file_ioctl fs/ioctl.c:509 [inline]
>  do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
>  ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>  __do_sys_ioctl fs/ioctl.c:720 [inline]
>  __se_sys_ioctl fs/ioctl.c:718 [inline]
>  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>  do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x447269
> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff
> 0f 83 3b d0 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffd58df6ad8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007ffd58df6ae0 RCX: 0000000000447269
> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
> RBP: 0000000000000000 R08: 0000000020003800 R09: 0000000000400e80
> R10: 00007ffd58df4f20 R11: 0000000000000246 R12: 0000000000404730
> R13: 00000000004047c0 R14: 0000000000000000 R15: 0000000000000000
> 
> Allocated by task 10006:
>  save_stack+0x23/0x90 mm/kasan/common.c:69
>  set_track mm/kasan/common.c:77 [inline]
>  __kasan_kmalloc mm/kasan/common.c:493 [inline]
>  __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:466
>  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:507
>  __do_kmalloc mm/slab.c:3655 [inline]
>  __kmalloc+0x163/0x770 mm/slab.c:3664
>  kmalloc include/linux/slab.h:557 [inline]
>  hcd_buffer_alloc+0x1c6/0x260 drivers/usb/core/buffer.c:132
>  usb_alloc_coherent+0x62/0x90 drivers/usb/core/usb.c:910
>  usbdev_mmap+0x1ce/0x790 drivers/usb/core/devio.c:224
>  call_mmap include/linux/fs.h:1875 [inline]
>  mmap_region+0xc35/0x1760 mm/mmap.c:1788
>  do_mmap+0x82e/0x1090 mm/mmap.c:1561
>  do_mmap_pgoff include/linux/mm.h:2374 [inline]
>  vm_mmap_pgoff+0x1c5/0x230 mm/util.c:391
>  ksys_mmap_pgoff+0x4aa/0x630 mm/mmap.c:1611
>  __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
>  __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
>  __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
>  do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 9516:
>  save_stack+0x23/0x90 mm/kasan/common.c:69
>  set_track mm/kasan/common.c:77 [inline]
>  __kasan_slab_free+0x102/0x150 mm/kasan/common.c:455
>  kasan_slab_free+0xe/0x10 mm/kasan/common.c:463
>  __cache_free mm/slab.c:3425 [inline]
>  kfree+0x10a/0x2c0 mm/slab.c:3756
>  tomoyo_init_log+0x15ba/0x2070 security/tomoyo/audit.c:293
>  tomoyo_supervisor+0x33f/0xef0 security/tomoyo/common.c:2095
>  tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
>  tomoyo_env_perm+0x18e/0x210 security/tomoyo/environ.c:63
>  tomoyo_environ security/tomoyo/domain.c:670 [inline]
>  tomoyo_find_next_domain+0x1354/0x1f6c security/tomoyo/domain.c:876
>  tomoyo_bprm_check_security security/tomoyo/tomoyo.c:107 [inline]
>  tomoyo_bprm_check_security+0x124/0x1b0 security/tomoyo/tomoyo.c:97
>  security_bprm_check+0x63/0xb0 security/security.c:750
>  search_binary_handler+0x71/0x570 fs/exec.c:1645
>  exec_binprm fs/exec.c:1701 [inline]
>  __do_execve_file.isra.0+0x1333/0x2340 fs/exec.c:1821
>  do_execveat_common fs/exec.c:1868 [inline]
>  do_execve fs/exec.c:1885 [inline]
>  __do_sys_execve fs/exec.c:1961 [inline]
>  __se_sys_execve fs/exec.c:1956 [inline]
>  __x64_sys_execve+0x8f/0xc0 fs/exec.c:1956
>  do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff888091e109c0
>  which belongs to the cache kmalloc-8k of size 8192
> The buggy address is located 2496 bytes to the left of
>  8192-byte region [ffff888091e109c0, ffff888091e129c0)
> The buggy address belongs to the page:
> page:ffffea0002478400 refcount:2 mapcount:0 mapping:ffff8880aa4021c0
> index:0x0 compound_mapcount: 0
> flags: 0x1fffc0000010200(slab|head)
> raw: 01fffc0000010200 ffffea000242e608 ffffea0002436708 ffff8880aa4021c0
> raw: 0000000000000000 ffff888091e109c0 0000000200000001 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff888091e0ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff888091e0ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff888091e10000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                    ^
>  ffff888091e10080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff888091e10100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
> 
> 
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 
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