[PATCH] riscv: Prevent a bad reference count on CPU nodes

Miquel Sabaté Solà
2024-09-13T08:02:30Z

When populating cache leaves we previously fetched the CPU device node
at the very beginning. But when ACPI is enabled we go through a
specific branch which returns early and does not call 'of_node_put' for
the node that was acquired.

Since we are not using a CPU device node for the ACPI code anyways, we
can simply move the initialization of it just passed the ACPI block, and
we are guaranteed to have an 'of_node_put' call for the acquired node.
This prevents a bad reference count of the CPU device node.

Moreover, the previous function did not check for errors when acquiring
the device node, so a return -ENOENT has been added for that case.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
I was wondering if this should also be sent to stable, but I have not seen
a report on it, and this is not responsible for an oops or anything like that.
So in the end I decided not to, but maybe you consider otherwise.

arch/riscv/kernel/cacheinfo.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
index d6c108c50cba..d32dfdba083e 100644
--- a/arch/riscv/kernel/cacheinfo.c
+++ b/arch/riscv/kernel/cacheinfo.c
@@ -75,8 +75,7 @@ int populate_cache_leaves(unsigned int cpu)
{
struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
struct cacheinfo *this_leaf = this_cpu_ci->info_list;
- struct device_node *np = of_cpu_device_node_get(cpu);
- struct device_node *prev = NULL;
+ struct device_node *np, *prev;
int levels = 1, level = 1;

if (!acpi_disabled) {
@@ -100,6 +99,10 @@ int populate_cache_leaves(unsigned int cpu)
return 0;
}

+ np = of_cpu_device_node_get(cpu);
+ if (!np)
+ return -ENOENT;
+
if (of_property_read_bool(np, "cache-size"))
ci_leaf_init(this_leaf++, CACHE_TYPE_UNIFIED, level);
if (of_property_read_bool(np, "i-cache-size"))
--
2.46.0