linux-kernel - possible deadlock in svm_vm_copy_asid

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Message-ID: <CAFkrUsirdW1j_nhFK23x99itQ7=eXqAWFK5xYo7Mjmg+8zPmLw@mail.gmail.com>
Date:   Tue, 4 Jan 2022 18:20:38 +0800
From:   kvartet <xyru1999@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Cc:     sunhao.th@...il.com
Subject: possible deadlock in svm_vm_copy_asid_from

Hello,

When using Syzkaller to fuzz the latest Linux kernel, the following
crash was triggered.

HEAD commit: a7904a538933 Linux 5.16-rc6
git tree: upstream
console output: https://paste.ubuntu.com/p/GCRXrYQmMN/plain/
kernel config: https://paste.ubuntu.com/p/FDDNHDxtwz/plain/
C reproducer: https://paste.ubuntu.com/p/gD2D5wthDK/plain/
Syzlang reproducer: https://paste.ubuntu.com/p/hTnbvmsW8r/plain/

============================================
WARNING: possible recursive locking detected
5.16.0-rc6 #9 Not tainted
--------------------------------------------
syz-executor.6/4919 is trying to acquire lock:
ffffc9000afbb250 (&kvm->lock){+.+.}-{3:3}, at: sev_lock_two_vms
arch/x86/kvm/svm/sev.c:1568 [inline]
ffffc9000afbb250 (&kvm->lock){+.+.}-{3:3}, at:
svm_vm_copy_asid_from+0x1bd/0x380 arch/x86/kvm/svm/sev.c:1988

but task is already holding lock:
ffffc9000a703250 (&kvm->lock){+.+.}-{3:3}, at: sev_lock_two_vms
arch/x86/kvm/svm/sev.c:1566 [inline]
ffffc9000a703250 (&kvm->lock){+.+.}-{3:3}, at:
svm_vm_copy_asid_from+0x188/0x380 arch/x86/kvm/svm/sev.c:1988

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&kvm->lock);
  lock(&kvm->lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz-executor.6/4919:
 #0: ffffc9000a703250 (&kvm->lock){+.+.}-{3:3}, at: sev_lock_two_vms
arch/x86/kvm/svm/sev.c:1566 [inline]
 #0: ffffc9000a703250 (&kvm->lock){+.+.}-{3:3}, at:
svm_vm_copy_asid_from+0x188/0x380 arch/x86/kvm/svm/sev.c:1988

stack backtrace:
CPU: 1 PID: 4919 Comm: syz-executor.6 Not tainted 5.16.0-rc6 #9
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
 check_deadlock kernel/locking/lockdep.c:2999 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire.cold+0x168/0x3c3 kernel/locking/lockdep.c:5027
 lock_acquire kernel/locking/lockdep.c:5637 [inline]
 lock_acquire+0x1ab/0x520 kernel/locking/lockdep.c:5602
 __mutex_lock_common kernel/locking/mutex.c:607 [inline]
 __mutex_lock+0x151/0x1610 kernel/locking/mutex.c:740
 sev_lock_two_vms arch/x86/kvm/svm/sev.c:1568 [inline]
 svm_vm_copy_asid_from+0x1bd/0x380 arch/x86/kvm/svm/sev.c:1988
 kvm_vm_ioctl_enable_cap+0xf8/0xc40 arch/x86/kvm/x86.c:5829
 kvm_vm_ioctl_enable_cap_generic
arch/x86/kvm/../../../virt/kvm/kvm_main.c:4241 [inline]
 kvm_vm_ioctl+0x3dd/0x23a0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4300
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fc4241dc89d
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc422b4dc28 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc4242fbf60 RCX: 00007fc4241dc89d
RDX: 0000000020000080 RSI: 000000004068aea3 RDI: 0000000000000004
RBP: 00007fc42424900d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc9816f67f R14: 00007fc4242fbf60 R15: 00007fc422b4ddc0
 </TASK>



If you fix this issue, please add the following tag to the commit:
Reported-by: Yiru Xu <xyru1999@...il.com>


Best Regards,
Yiru