[PATCH 6.6.y 1/2] most: core: fix resource leak in most_register_interface error paths

[Artem Dinaburg <artem@trailofbits.com>]

From: Navaneeth K <knavaneeth786@gmail.com>

[ Upstream commit 1f4c9d8a1021281750c6cda126d6f8a40cc24e71 ]

The function most_register_interface() did not correctly release resources
if it failed early (before registering the device). In these cases, it
returned an error code immediately, leaking the memory allocated for the
interface.

Fix this by initializing the device early via device_initialize() and
calling put_device() on all error paths.

The most_register_interface() is expected to call put_device() on
error which frees the resources allocated in the caller. The
put_device() either calls release_mdev() or dim2_release(),
depending on the caller.

Switch to using device_add() instead of device_register() to handle
the split initialization.

Acked-by: Abdun Nihaal <abdun.nihaal@gmail.com>
Signed-off-by: Navaneeth K <knavaneeth786@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/20251127165337.19172-1-knavaneeth786@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Assisted-by: LLM
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
Hi,

Please consider this backport of the fix for CVE-2025-71272 to 6.6.y.

The code changes are identical to upstream.

The complete fix is already present in 6.12.y, 6.18.y and 7.2.y.

Build-tested only as part of a cumulative 6.6.y series: x86_64 objects
(allmodconfig, CONFIG_WERROR=y); no runtime testing.

Thanks,
Artem Dinaburg

 drivers/most/core.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/most/core.c b/drivers/most/core.c
index 5d073b3d2796754d278e4de84de0eb3bf43dd8d0..0fbf06d34e0b968e6444877af981322a3793d406 100644
--- a/drivers/most/core.c
+++ b/drivers/most/core.c
@@ -1286,15 +1286,19 @@ int most_register_interface(struct most_interface *iface)
 	    !iface->poison_channel || (iface->num_channels > MAX_CHANNELS))
 		return -EINVAL;
 
+	device_initialize(iface->dev);
+
 	id = ida_simple_get(&mdev_id, 0, 0, GFP_KERNEL);
 	if (id < 0) {
 		dev_err(iface->dev, "Failed to allocate device ID\n");
+		put_device(iface->dev);
 		return id;
 	}
 
 	iface->p = kzalloc(sizeof(*iface->p), GFP_KERNEL);
 	if (!iface->p) {
 		ida_simple_remove(&mdev_id, id);
+		put_device(iface->dev);
 		return -ENOMEM;
 	}
 
@@ -1304,7 +1308,7 @@ int most_register_interface(struct most_interface *iface)
 	iface->dev->bus = &mostbus;
 	iface->dev->groups = interface_attr_groups;
 	dev_set_drvdata(iface->dev, iface);
-	if (device_register(iface->dev)) {
+	if (device_add(iface->dev)) {
 		dev_err(iface->dev, "Failed to register interface device\n");
 		kfree(iface->p);
 		put_device(iface->dev);