From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: jmattson@google.com, wanpengli@tencent.com,
Junaid Shahid <junaids@google.com>
Subject: [PATCH 2/2] KVM: fix placement of refcount initialization
Date: Mon, 11 Nov 2019 14:25:41 +0100 [thread overview]
Message-ID: <1573478741-30959-3-git-send-email-pbonzini@redhat.com> (raw)
In-Reply-To: <1573478741-30959-1-git-send-email-pbonzini@redhat.com>
Reported by syzkaller:
=============================
WARNING: suspicious RCU usage
-----------------------------
./include/linux/kvm_host.h:536 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
no locks held by repro_11/12688.
stack backtrace:
Call Trace:
dump_stack+0x7d/0xc5
lockdep_rcu_suspicious+0x123/0x170
kvm_dev_ioctl+0x9a9/0x1260 [kvm]
do_vfs_ioctl+0x1a1/0xfb0
ksys_ioctl+0x6d/0x80
__x64_sys_ioctl+0x73/0xb0
do_syscall_64+0x108/0xaa0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Commit a97b0e773e4 (kvm: call kvm_arch_destroy_vm if vm creation fails)
sets users_count to 1 before kvm_arch_init_vm(), however, if kvm_arch_init_vm()
fails, we need to decrease this count. By moving it earlier, we can push
the decrease to out_err_no_arch_destroy_vm without introducing yet another
error label.
syzkaller source: https://syzkaller.appspot.com/x/repro.c?x=15209b84e00000
Reported-by: syzbot+75475908cd0910f141ee@syzkaller.appspotmail.com
Fixes: a97b0e773e49 ("kvm: call kvm_arch_destroy_vm if vm creation fails")
Cc: Jim Mattson <jmattson@google.com>
Analyzed-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
virt/kvm/kvm_main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e22ff63e5b1a..e7a07132cd7f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -650,6 +650,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
if (init_srcu_struct(&kvm->irq_srcu))
goto out_err_no_irq_srcu;
+ refcount_set(&kvm->users_count, 1);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
struct kvm_memslots *slots = kvm_alloc_memslots();
@@ -667,7 +668,6 @@ static struct kvm *kvm_create_vm(unsigned long type)
goto out_err_no_arch_destroy_vm;
}
- refcount_set(&kvm->users_count, 1);
r = kvm_arch_init_vm(kvm, type);
if (r)
goto out_err_no_arch_destroy_vm;
@@ -696,8 +696,8 @@ static struct kvm *kvm_create_vm(unsigned long type)
hardware_disable_all();
out_err_no_disable:
kvm_arch_destroy_vm(kvm);
- WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count));
out_err_no_arch_destroy_vm:
+ WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count));
for (i = 0; i < KVM_NR_BUSES; i++)
kfree(kvm_get_bus(kvm, i));
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
--
1.8.3.1
next prev parent reply other threads:[~2019-11-11 13:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-11 13:25 [PATCH 0/2] KVM: fix issues with kvm_create_vm failures Paolo Bonzini
2019-11-11 13:25 ` [PATCH 1/2] KVM: Fix NULL-ptr deref after kvm_create_vm fails Paolo Bonzini
2019-11-12 18:49 ` Jim Mattson
2019-11-11 13:25 ` Paolo Bonzini [this message]
2019-11-12 18:50 ` [PATCH 2/2] KVM: fix placement of refcount initialization Jim Mattson
2019-11-12 0:52 ` [PATCH 0/2] KVM: fix issues with kvm_create_vm failures Wanpeng Li
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