* [PATCH] KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op()
@ 2022-06-28 13:30 Vitaly Kuznetsov
2022-07-07 17:34 ` Sean Christopherson
0 siblings, 1 reply; 3+ messages in thread
From: Vitaly Kuznetsov @ 2022-06-28 13:30 UTC (permalink / raw)
To: kvm, Paolo Bonzini
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, linux-hyperv, linux-kernel
'vector' and 'trig_mode' fields of 'struct kvm_lapic_irq' are left
uninitialized in kvm_pv_kick_cpu_op(). While these fields are normally
not needed for APIC_DM_REMRD, they're still referenced by
__apic_accept_irq() for trace_kvm_apic_accept_irq(). Fully initialize
the structure to avoid consuming random stack memory.
Fixes: a183b638b61c ("KVM: x86: make apic_accept_irq tracepoint more generic")
Reported-by: syzbot+d6caa905917d353f0d07@syzkaller.appspotmail.com
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/x86.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 567d13405445..8a98608dad4f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9340,15 +9340,17 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
*/
static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid)
{
- struct kvm_lapic_irq lapic_irq;
-
- lapic_irq.shorthand = APIC_DEST_NOSHORT;
- lapic_irq.dest_mode = APIC_DEST_PHYSICAL;
- lapic_irq.level = 0;
- lapic_irq.dest_id = apicid;
- lapic_irq.msi_redir_hint = false;
+ struct kvm_lapic_irq lapic_irq = {
+ .vector = 0,
+ .delivery_mode = APIC_DM_REMRD,
+ .dest_mode = APIC_DEST_PHYSICAL,
+ .level = false,
+ .trig_mode = 0,
+ .shorthand = APIC_DEST_NOSHORT,
+ .dest_id = apicid,
+ .msi_redir_hint = false
+ };
- lapic_irq.delivery_mode = APIC_DM_REMRD;
kvm_irq_delivery_to_apic(kvm, NULL, &lapic_irq, NULL);
}
--
2.35.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op() 2022-06-28 13:30 [PATCH] KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op() Vitaly Kuznetsov @ 2022-07-07 17:34 ` Sean Christopherson 2022-07-08 12:44 ` Vitaly Kuznetsov 0 siblings, 1 reply; 3+ messages in thread From: Sean Christopherson @ 2022-07-07 17:34 UTC (permalink / raw) To: Vitaly Kuznetsov Cc: kvm, Paolo Bonzini, Wanpeng Li, Jim Mattson, linux-hyperv, linux-kernel On Tue, Jun 28, 2022, Vitaly Kuznetsov wrote: > 'vector' and 'trig_mode' fields of 'struct kvm_lapic_irq' are left > uninitialized in kvm_pv_kick_cpu_op(). While these fields are normally > not needed for APIC_DM_REMRD, they're still referenced by > __apic_accept_irq() for trace_kvm_apic_accept_irq(). Fully initialize > the structure to avoid consuming random stack memory. > > Fixes: a183b638b61c ("KVM: x86: make apic_accept_irq tracepoint more generic") > Reported-by: syzbot+d6caa905917d353f0d07@syzkaller.appspotmail.com > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > arch/x86/kvm/x86.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 567d13405445..8a98608dad4f 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9340,15 +9340,17 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr, > */ > static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid) > { > - struct kvm_lapic_irq lapic_irq; > - > - lapic_irq.shorthand = APIC_DEST_NOSHORT; > - lapic_irq.dest_mode = APIC_DEST_PHYSICAL; > - lapic_irq.level = 0; > - lapic_irq.dest_id = apicid; > - lapic_irq.msi_redir_hint = false; > + struct kvm_lapic_irq lapic_irq = { > + .vector = 0, > + .delivery_mode = APIC_DM_REMRD, > + .dest_mode = APIC_DEST_PHYSICAL, > + .level = false, > + .trig_mode = 0, > + .shorthand = APIC_DEST_NOSHORT, > + .dest_id = apicid, > + .msi_redir_hint = false > + }; What if we rely on the compiler to zero-initialize omitted fields? E.g. /* * All other fields are unused for APIC_DM_REMRD, but may be consumed by * common code, e.g. for tracing. Defer initialization to the compiler. */ struct kvm_lapic_irq lapic_irq = { .delivery_mode = APIC_DM_REMRD, .dest_mode = APIC_DEST_PHYSICAL, .shorthand = APIC_DEST_NOSHORT, .dest_id = apicid, }; KVM doesn't actually care about the vector, level, trig_mode, etc... for its magic magic DM_REMRD, i.e. using 0/false is completely arbitrary. > > - lapic_irq.delivery_mode = APIC_DM_REMRD; > kvm_irq_delivery_to_apic(kvm, NULL, &lapic_irq, NULL); > } > > -- > 2.35.3 > ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op() 2022-07-07 17:34 ` Sean Christopherson @ 2022-07-08 12:44 ` Vitaly Kuznetsov 0 siblings, 0 replies; 3+ messages in thread From: Vitaly Kuznetsov @ 2022-07-08 12:44 UTC (permalink / raw) To: Sean Christopherson Cc: kvm, Paolo Bonzini, Wanpeng Li, Jim Mattson, linux-hyperv, linux-kernel Sean Christopherson <seanjc@google.com> writes: > On Tue, Jun 28, 2022, Vitaly Kuznetsov wrote: >> 'vector' and 'trig_mode' fields of 'struct kvm_lapic_irq' are left >> uninitialized in kvm_pv_kick_cpu_op(). While these fields are normally >> not needed for APIC_DM_REMRD, they're still referenced by >> __apic_accept_irq() for trace_kvm_apic_accept_irq(). Fully initialize >> the structure to avoid consuming random stack memory. >> >> Fixes: a183b638b61c ("KVM: x86: make apic_accept_irq tracepoint more generic") >> Reported-by: syzbot+d6caa905917d353f0d07@syzkaller.appspotmail.com >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> >> --- >> arch/x86/kvm/x86.c | 18 ++++++++++-------- >> 1 file changed, 10 insertions(+), 8 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 567d13405445..8a98608dad4f 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -9340,15 +9340,17 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr, >> */ >> static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid) >> { >> - struct kvm_lapic_irq lapic_irq; >> - >> - lapic_irq.shorthand = APIC_DEST_NOSHORT; >> - lapic_irq.dest_mode = APIC_DEST_PHYSICAL; >> - lapic_irq.level = 0; >> - lapic_irq.dest_id = apicid; >> - lapic_irq.msi_redir_hint = false; >> + struct kvm_lapic_irq lapic_irq = { >> + .vector = 0, >> + .delivery_mode = APIC_DM_REMRD, >> + .dest_mode = APIC_DEST_PHYSICAL, >> + .level = false, >> + .trig_mode = 0, >> + .shorthand = APIC_DEST_NOSHORT, >> + .dest_id = apicid, >> + .msi_redir_hint = false >> + }; > > What if we rely on the compiler to zero-initialize omitted fields? E.g. > > /* > * All other fields are unused for APIC_DM_REMRD, but may be consumed by > * common code, e.g. for tracing. Defer initialization to the compiler. > */ > struct kvm_lapic_irq lapic_irq = { > .delivery_mode = APIC_DM_REMRD, > .dest_mode = APIC_DEST_PHYSICAL, > .shorthand = APIC_DEST_NOSHORT, > .dest_id = apicid, > }; > > KVM doesn't actually care about the vector, level, trig_mode, etc... for its magic > magic DM_REMRD, i.e. using 0/false is completely arbitrary. Honestly, I just always forget whether zero-initializing of omitted fields is a de-facto or de-jure standard. We don't care much whether these fields are zero of not but some random values in tracing may confuse an unprepared reader. I'll send v2 with your amendment. > >> >> - lapic_irq.delivery_mode = APIC_DM_REMRD; >> kvm_irq_delivery_to_apic(kvm, NULL, &lapic_irq, NULL); >> } >> >> -- >> 2.35.3 >> > -- Vitaly ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-07-08 12:44 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-06-28 13:30 [PATCH] KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op() Vitaly Kuznetsov 2022-07-07 17:34 ` Sean Christopherson 2022-07-08 12:44 ` Vitaly Kuznetsov
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