[Xen-devel] [PATCH for-4.13 v3] xen/arm: fix buf size in make_cpus_node

[Stefano Stabellini <sstabellini@kernel.org>]

The size of buf is calculated wrongly: the number is printed as a
hexadecimal number, so we need 8 bytes for 32bit, not 10 bytes.

As a result, it should be sizeof("cpu@") + 8 bytes for a 32-bit number +
1 byte for \0. Total = 13.

mpidr_aff is 64-bit, however, only bits [0-23] are used. Add a check for
that.

Fixes: c81a791d34 (xen/arm: Set 'reg' of cpu node for dom0 to match MPIDR's affinity)
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
---
Changes in v3:
- make sure only [23:0] bits are used in mpidr_aff
- clarify that we only need 32bit for buf writes

Changes in v2:
- patch added
---
 xen/arch/arm/domain_build.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 921b054520..d5ee639548 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -789,7 +789,7 @@ static int __init make_cpus_node(const struct domain *d, void *fdt)
     const void *compatible = NULL;
     u32 len;
     /* Placeholder for cpu@ + a 32-bit number + \0 */
-    char buf[15];
+    char buf[13];
     u32 clock_frequency;
     bool clock_valid;
     uint64_t mpidr_aff;
@@ -847,8 +847,18 @@ static int __init make_cpus_node(const struct domain *d, void *fdt)
          * the MPIDR's affinity bits. We will use AFF0 and AFF1 when
          * constructing the reg value of the guest at the moment, for it
          * is enough for the current max vcpu number.
+         *
+         * We only deal with AFF{0, 1, 2} stored in bits [23:0] at the
+         * moment.
          */
         mpidr_aff = vcpuid_to_vaffinity(cpu);
+        if ( (mpidr_aff & ~GENMASK_ULL(23, 0)) != 0 )
+        {
+            printk(XENLOG_ERR "Unable to handle MPIDR AFFINITY 0x%"PRIx64"\n", 
+                   mpidr_aff);
+            return -EINVAL;
+        }
+
         dt_dprintk("Create cpu@%"PRIx64" (logical CPUID: %d) node\n",
                    mpidr_aff, cpu);
 
-- 
2.17.1


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