[Xen-devel] [PATCH FOR-4.10] xen/arm: guest_walk: Fix check again the IPS

[Julien Grall <julien.grall@xxxxxxxxxx>]

The function get_ipa_output_size is check whether the input size
configured by the guest is valid and will return it.

The check is done with the IPS already shifted against
TCR_EL1_IPS_48_BIT. However the constant has been defined with the
shift included, resulting the check always been false.

Fix it by doing the check on the non-shifted value.

This was introduced by commit 7d623b358a "arm/mem_access: Add long-descriptor
based gpt" introduced software page-table walk for stage-1.

Coverity-ID: 1457707
Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

---

Cc: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
---
 xen/arch/arm/guest_walk.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/guest_walk.c b/xen/arch/arm/guest_walk.c
index c38bedcf65..a6de325572 100644
--- a/xen/arch/arm/guest_walk.c
+++ b/xen/arch/arm/guest_walk.c
@@ -185,7 +185,7 @@ static int guest_walk_sd(const struct vcpu *v,
 static int get_ipa_output_size(struct domain *d, register_t tcr,
                                unsigned int *output_size)
 {
-    unsigned int ips;
+    register_t ips;
 
     static const unsigned int ipa_sizes[7] = {
         TCR_EL1_IPS_32_BIT_VAL,
@@ -200,7 +200,7 @@ static int get_ipa_output_size(struct domain *d, register_t 
tcr,
     if ( is_64bit_domain(d) )
     {
         /* Get the intermediate physical address size. */
-        ips = (tcr & TCR_EL1_IPS_MASK) >> TCR_EL1_IPS_SHIFT;
+        ips = tcr & TCR_EL1_IPS_MASK;
 
         /*
          * Return an error on reserved IPA output-sizes and if the IPA
@@ -211,7 +211,7 @@ static int get_ipa_output_size(struct domain *d, register_t 
tcr,
         if ( ips > TCR_EL1_IPS_48_BIT )
             return -EFAULT;
 
-        *output_size = ipa_sizes[ips];
+        *output_size = ipa_sizes[ips >> TCR_EL1_IPS_SHIFT];
     }
     else
         *output_size = TCR_EL1_IPS_40_BIT_VAL;
-- 
2.11.0


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