make_cpus_node() is using a static buffer to generate the FDT node name.
While mpdir_aff is a 64-bit integer, we only ever use the bits [23:0] as
only AFF{0, 1, 2} are supported for now.
To avoid any potential issues in the future, check that mpdir_aff has
only bits [23:0] set.
Take the opportunity to reduce the size of the buffer. Indeed, only 8
characters are needed to print a 32-bit hexadecimal number. So
sizeof("cpu@") + 8 + 1 (for '\0') = 13 characters is sufficient.
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>
---
Changes in v4:
- commit message
- in-code comments
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 | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 921b054520..38adb6e954 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -788,8 +788,8 @@ static int __init make_cpus_node(const struct domain *d, void *fdt)
unsigned int cpu;
const void *compatible = NULL;
u32 len;
- /* Placeholder for cpu@ + a 32-bit number + \0 */
- char buf[15];
+ /* Placeholder for cpu@ + a 32-bit hexadecimal number + \0 */
+ char buf[13];
u32 clock_frequency;
bool clock_valid;
uint64_t mpidr_aff;
@@ -847,11 +847,26 @@ 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);
+ /*
+ * We use PRIx64 because mpidr_aff is a 64bit integer. However,
+ * only bits [23:0] are used, thus, we are sure it will fit in
+ * buf.
+ */
snprintf(buf, sizeof(buf), "cpu@%"PRIx64, mpidr_aff);
res = fdt_begin_node(fdt, buf);
if ( res )
--
2.17.1
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On 10.10.19 02:42, Stefano Stabellini wrote: > make_cpus_node() is using a static buffer to generate the FDT node name. > While mpdir_aff is a 64-bit integer, we only ever use the bits [23:0] as > only AFF{0, 1, 2} are supported for now. > > To avoid any potential issues in the future, check that mpdir_aff has > only bits [23:0] set. > > Take the opportunity to reduce the size of the buffer. Indeed, only 8 > characters are needed to print a 32-bit hexadecimal number. So > sizeof("cpu@") + 8 + 1 (for '\0') = 13 characters is sufficient. > > 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> Juergen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Hi Stefano, On 10/10/19 1:42 AM, Stefano Stabellini wrote: > make_cpus_node() is using a static buffer to generate the FDT node name. > While mpdir_aff is a 64-bit integer, we only ever use the bits [23:0] as > only AFF{0, 1, 2} are supported for now. > > To avoid any potential issues in the future, check that mpdir_aff has > only bits [23:0] set. > > Take the opportunity to reduce the size of the buffer. Indeed, only 8 > characters are needed to print a 32-bit hexadecimal number. So > sizeof("cpu@") + 8 + 1 (for '\0') = 13 characters is sufficient. > > 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> Reviewed-by: Julien Grall <julien.grall@arm.com> Cheers, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
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