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authorChristian Borntraeger <borntraeger@de.ibm.com>2017-09-13 14:17:22 +0200
committerRadim Krčmář <rkrcmar@redhat.com>2017-09-13 16:40:24 +0200
commit021086e383fa408a219f6c6541b37f495f59d576 (patch)
treee5921f047d3a37191aa366af6ace450029f52867 /virt
parent2f173d2688559a6f85643d38a2ad6f45eb420c42 (diff)
downloadlinux-021086e383fa408a219f6c6541b37f495f59d576.tar.bz2
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')
-rw-r--r--virt/kvm/kvm_main.c1
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++)