[PATCH 1/2] ARM: vexpress: fix device_node refcount leak in vexpress_flags_set()

[Weigang He <geoffreyhe2@gmail.com>]

vexpress_flags_set() obtains a reference to the "arm,vexpress-sysreg"
device node via of_find_compatible_node() and passes it to of_iomap(),
but never calls of_node_put() on it. of_iomap() only reads the node's
reg property to create the mapping and does not take ownership, so the
node reference is leaked. The function runs from the __init SMP prepare
path and caches the mapping in a static, so this is a one-shot leak of a
single refcount during boot, with no functional impact.

The lookup was added to drivers/mfd/vexpress-sysreg.c by the commit
below and later moved here by commit 9b06fc39084e ("ARM: vexpress: Move
vexpress_flags_set() into arch code").

Annotate node with the __free(device_node) cleanup attribute so the
reference is released when it goes out of scope.

Found by static analysis tool CodeQL.

Fixes: 974cc7b93441 ("mfd: vexpress: Define the device as MFD cells")
Assisted-by: LLM codeql
Signed-off-by: Weigang He <geoffreyhe2@gmail.com>
---

Notes:
    Compile-tested only (ARCH=arm multi_v7_defconfig, W=1). Not tested on
    hardware; I have no Versatile Express board.
    
    The CodeQL query behind this report was synthesized with LLM assistance,
    and the fix and changelog were drafted with LLM assistance; I have
    reviewed them.

 arch/arm/mach-versatile/v2m.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-versatile/v2m.c b/arch/arm/mach-versatile/v2m.c
index 79afdf2a90b6f..c86b38386cf7c 100644
--- a/arch/arm/mach-versatile/v2m.c
+++ b/arch/arm/mach-versatile/v2m.c
@@ -13,8 +13,8 @@ void vexpress_flags_set(u32 data)
 	static void __iomem *base;
 
 	if (!base) {
-		struct device_node *node = of_find_compatible_node(NULL, NULL,
-				"arm,vexpress-sysreg");
+		struct device_node *node __free(device_node) =
+			of_find_compatible_node(NULL, NULL, "arm,vexpress-sysreg");
 
 		base = of_iomap(node, 0);
 	}
-- 
2.43.0