From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Tue, 27 Jun 2017 17:45:03 +0000 (+0100)
Subject: xen/pt: Avoid NULL dereference in hvm_pirq_eoi()
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~1896
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=34c06658c100414edc7bbbf23e284019facc965e;p=xen.git

xen/pt: Avoid NULL dereference in hvm_pirq_eoi()

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@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
---

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 523d089006..d9fea2c638 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 25e3fb4078..ffeaf70be6 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 182caa44be..abb1f1ccda 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);