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| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2017-09-13 14:17:22 +0200 |
|---|---|---|
| committer | Radim Krčmář <rkrcmar@redhat.com> | 2017-09-13 16:40:24 +0200 |
| commit | 021086e383fa408a219f6c6541b37f495f59d576 (patch) | |
| tree | e5921f047d3a37191aa366af6ace450029f52867 /virt/kvm/kvm_main.c | |
| parent | 2f173d2688559a6f85643d38a2ad6f45eb420c42 (diff) | |
| download | lwn-021086e383fa408a219f6c6541b37f495f59d576.tar.gz lwn-021086e383fa408a219f6c6541b37f495f59d576.zip | |
KVM: fix rcu warning on VM_CREATE errors
commit 3898da947bba ("KVM: avoid using rcu_dereference_protected") can
trigger the following lockdep/rcu splat if the VM_CREATE ioctl fails,
for example if kvm_arch_init_vm fails:
WARNING: suspicious RCU usage
4.13.0+ #105 Not tainted
-----------------------------
./include/linux/kvm_host.h:481 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
no locks held by qemu-system-s39/79.
stack backtrace:
CPU: 0 PID: 79 Comm: qemu-system-s39 Not tainted 4.13.0+ #105
Hardware name: IBM 2964 NC9 704 (KVM/Linux)
Call Trace:
([<00000000001140b2>] show_stack+0xea/0xf0)
[<00000000008a68a4>] dump_stack+0x94/0xd8
[<0000000000134c12>] kvm_dev_ioctl+0x372/0x7a0
[<000000000038f940>] do_vfs_ioctl+0xa8/0x6c8
[<0000000000390004>] SyS_ioctl+0xa4/0xb8
[<00000000008c7a8c>] system_call+0xc4/0x27c
no locks held by qemu-system-s39/79.
We have to reset the just created users_count back to 0 to
tell the check to not trigger.
Reported-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Fixes: 3898da947bba ("KVM: avoid using rcu_dereference_protected")
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'virt/kvm/kvm_main.c')
| -rw-r--r-- | virt/kvm/kvm_main.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6ed1c2021198..2d7df5cc955b 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -674,6 +674,7 @@ out_err_no_irq_srcu: out_err_no_srcu: hardware_disable_all(); out_err_no_disable: + refcount_set(&kvm->users_count, 0); for (i = 0; i < KVM_NR_BUSES; i++) kfree(kvm_get_bus(kvm, i)); for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) |