[PATCH v5 18/25] soundwire: amd: delay *sdw_ctx publication until after startup succeeds

[Vijendar Mukunda <Vijendar.Mukunda@amd.com>]

sdw_amd_probe() published *sdw_ctx immediately after probe_controller()
returned, before sdw_amd_startup() ran.  Two problems follow from this:

1. If sdw_amd_startup() fails, the error was returned directly, leaving
   *sdw_ctx pointing to an allocated context whose platform devices were
   already registered.  The caller has no way to distinguish this from a
   genuine probe success, so the context and devices leak.

2. A concurrent ACP IRQ handler on another CPU can read the non-NULL
   adata->sdw pointer between the sdw_amd_exit() teardown and the
   *sdw_ctx = NULL assignment, and dereference a freed context.

Fix both by using a local variable for the context, running
sdw_amd_startup() against it, and only writing *sdw_ctx after startup
succeeds.  On failure sdw_amd_exit() is called on the local pointer and
the function returns without touching *sdw_ctx, so callers never observe
a partially-initialised or freed context.

Fixes: ed5e8741b8db ("soundwire: amd: refactor amd soundwire manager device node creation")
Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
---
 drivers/soundwire/amd_init.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/soundwire/amd_init.c b/drivers/soundwire/amd_init.c
index 032697ea3590..ce40b1e5dbf3 100644
--- a/drivers/soundwire/amd_init.c
+++ b/drivers/soundwire/amd_init.c
@@ -176,11 +176,20 @@ static int sdw_amd_startup(struct sdw_amd_ctx *ctx)
 
 int sdw_amd_probe(struct sdw_amd_res *res, struct sdw_amd_ctx **sdw_ctx)
 {
-	*sdw_ctx = sdw_amd_probe_controller(res);
-	if (!*sdw_ctx)
+	struct sdw_amd_ctx *ctx;
+	int ret;
+
+	ctx = sdw_amd_probe_controller(res);
+	if (!ctx)
 		return -ENODEV;
 
-	return sdw_amd_startup(*sdw_ctx);
+	ret = sdw_amd_startup(ctx);
+	if (ret) {
+		sdw_amd_exit(ctx);
+		return ret;
+	}
+	*sdw_ctx = ctx;
+	return 0;
 }
 EXPORT_SYMBOL_NS(sdw_amd_probe, "SOUNDWIRE_AMD_INIT");
 
-- 
2.53.0