Re: KASAN: vmalloc-out-of-bounds Write in kvm_dev_ioctl_get_cpuid

[Paolo Bonzini]

On 04/12/19 05:15, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:ÂÂÂ 596cf45c Merge branch 'akpm' (patches from Andrew)
> git tree:ÂÂÂÂÂÂ upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=103acb7ae00000
> kernel config:Â https://syzkaller.appspot.com/x/.config?x=8eb54eee6e6ca4a7
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=e3f4897236c4eeb8af4f
> compiler:ÂÂÂÂÂÂ gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:ÂÂÂÂÂ https://syzkaller.appspot.com/x/repro.syz?x=15b87c82e00000
> C reproducer:ÂÂ https://syzkaller.appspot.com/x/repro.c?x=11250f36e00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+e3f4897236c4eeb8af4f@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ==================================================================
> BUG: KASAN: vmalloc-out-of-bounds in __do_cpuid_func_emulated
> arch/x86/kvm/cpuid.c:323 [inline]
> BUG: KASAN: vmalloc-out-of-bounds in do_cpuid_func
> arch/x86/kvm/cpuid.c:814 [inline]
> BUG: KASAN: vmalloc-out-of-bounds in do_cpuid_func
> arch/x86/kvm/cpuid.c:810 [inline]
> BUG: KASAN: vmalloc-out-of-bounds in kvm_dev_ioctl_get_cpuid+0xad7/0xb0b
> arch/x86/kvm/cpuid.c:891
> Write of size 4 at addr ffffc90000d36050 by task syz-executor490/9767
> 
> CPU: 1 PID: 9767 Comm: syz-executor490 Not tainted 5.4.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> Â__dump_stack lib/dump_stack.c:77 [inline]
> Âdump_stack+0x197/0x210 lib/dump_stack.c:118
> Âprint_address_description.constprop.0.cold+0x5/0x30b mm/kasan/report.c:374
> Â__kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
> Âkasan_report+0x12/0x20 mm/kasan/common.c:638
> Â__asan_report_store4_noabort+0x17/0x20 mm/kasan/generic_report.c:139
> Â__do_cpuid_func_emulated arch/x86/kvm/cpuid.c:323 [inline]
> Âdo_cpuid_func arch/x86/kvm/cpuid.c:814 [inline]
> Âdo_cpuid_func arch/x86/kvm/cpuid.c:810 [inline]
> Âkvm_dev_ioctl_get_cpuid+0xad7/0xb0b arch/x86/kvm/cpuid.c:891
> Âkvm_arch_dev_ioctl+0x300/0x4b0 arch/x86/kvm/x86.c:3387
> Âkvm_dev_ioctl+0x127/0x17d0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3593
> Âvfs_ioctl fs/ioctl.c:47 [inline]
> Âfile_ioctl fs/ioctl.c:539 [inline]
> Âdo_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726
> Âksys_ioctl+0xab/0xd0 fs/ioctl.c:743
> Â__do_sys_ioctl fs/ioctl.c:750 [inline]
> Â__se_sys_ioctl fs/ioctl.c:748 [inline]
> Â__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748
> Âdo_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
> Âentry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x440159
> 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffd106332c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440159
> RDX: 0000000020000080 RSI: 00000000c008ae09 RDI: 0000000000000003
> RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004019e0
> R13: 0000000000401a70 R14: 0000000000000000 R15: 0000000000000000
> 
> 
> Memory state around the buggy address:
> Âffffc90000d35f00: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
> Âffffc90000d35f80: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
>> ffffc90000d36000: 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9
> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ^
> Âffffc90000d36080: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
> Âffffc90000d36100: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
> ==================================================================
> 
> 
> ---
> 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:
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> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 

Ouch, this is bad.  Sending a patch now.

Paolo