[Xen-devel] [PATCH 2/2] xen/pt: Avoid NULL dereference in hvm_pirq_eoi()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Coverity warns that pirq_dpci unconditionally dereferences a NULL pointer.
This warning appears to be triggered by pirq_dpci() which is a hidden ternary
expression.  In reality, it appears that both callers pass a non-NULL pirq
parameter, so the code is ok in practice.

Rearange the logic to fail-safe, which should quiesce Coverity.

Clean up bool_t => bool and trailing whitespace for hvm_domain_use_pirq()
while auditing this area.

No (intended) functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/irq.c           |  5 ++---
 xen/drivers/passthrough/io.c | 10 +++++++++-
 xen/include/asm-x86/irq.h    |  2 +-
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 523d089..d9fea2c 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -2530,10 +2530,9 @@ void arch_evtchn_bind_pirq(struct domain *d, int pirq)
     spin_unlock_irqrestore(&desc->lock, flags);
 }
 
-bool_t hvm_domain_use_pirq(const struct domain *d, const struct pirq *pirq)
+bool hvm_domain_use_pirq(const struct domain *d, const struct pirq *pirq)
 {
-    return is_hvm_domain(d) && pirq &&
-           pirq->arch.hvm.emuirq != IRQ_UNBOUND; 
+    return is_hvm_domain(d) && pirq && pirq->arch.hvm.emuirq != IRQ_UNBOUND;
 }
 
 static int allocate_pirq(struct domain *d, int index, int pirq, int irq,
diff --git a/xen/drivers/passthrough/io.c b/xen/drivers/passthrough/io.c
index 25e3fb4..ffeaf70 100644
--- a/xen/drivers/passthrough/io.c
+++ b/xen/drivers/passthrough/io.c
@@ -912,7 +912,15 @@ static void hvm_dirq_assist(struct domain *d, struct 
hvm_pirq_dpci *pirq_dpci)
 static void hvm_pirq_eoi(struct pirq *pirq,
                          const union vioapic_redir_entry *ent)
 {
-    struct hvm_pirq_dpci *pirq_dpci = pirq_dpci(pirq);
+    struct hvm_pirq_dpci *pirq_dpci;
+
+    if ( !pirq )
+    {
+        ASSERT_UNREACHABLE();
+        return;
+    }
+
+    pirq_dpci = pirq_dpci(pirq);
 
     /*
      * No need to get vector lock for timer
diff --git a/xen/include/asm-x86/irq.h b/xen/include/asm-x86/irq.h
index 182caa4..abb1f1c 100644
--- a/xen/include/asm-x86/irq.h
+++ b/xen/include/asm-x86/irq.h
@@ -145,7 +145,7 @@ int get_free_pirqs(struct domain *, unsigned int nr);
 void free_domain_pirqs(struct domain *d);
 int map_domain_emuirq_pirq(struct domain *d, int pirq, int irq);
 int unmap_domain_pirq_emuirq(struct domain *d, int pirq);
-bool_t hvm_domain_use_pirq(const struct domain *, const struct pirq *);
+bool hvm_domain_use_pirq(const struct domain *, const struct pirq *);
 
 /* Reset irq affinities to match the given CPU mask. */
 void fixup_irqs(const cpumask_t *mask, bool_t verbose);
-- 
2.1.4


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