[PATCH v5 2/7] firmware: samsung: acpm: Fix mailbox channel leak on probe error

[Tudor Ambarus]

Sashiko identified the leak at [1].

The ACPM driver allocates hardware mailbox channels using
`mbox_request_channel()` during `acpm_channels_init()`. However, the
driver lacked a `.remove` callback and did not free these channels on
subsequent error paths inside `acpm_probe()`.

Additionally, if `acpm_achan_alloc_cmds()` failed during the channel
initialization loop, the function returned immediately, bypassing the
manual cleanup and permanently leaking any channels successfully
requested in previous loop iterations.

Fix this by modifying `acpm_free_mbox_chans()` to match the `devres`
action signature and registering it via `devm_add_action_or_reset()`.

Cc: stable at vger.kernel.org
Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver")
Closes: https://sashiko.dev/#/patchset/20260420-acpm-tmu-v3-0-3dc8e93f0b26%40linaro.org [1]
Signed-off-by: Tudor Ambarus <tudor.ambarus at linaro.org>
---
 drivers/firmware/samsung/exynos-acpm.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/samsung/exynos-acpm.c b/drivers/firmware/samsung/exynos-acpm.c
index e95edc350efa..9766425a44ab 100644
--- a/drivers/firmware/samsung/exynos-acpm.c
+++ b/drivers/firmware/samsung/exynos-acpm.c
@@ -527,10 +527,11 @@ static int acpm_achan_alloc_cmds(struct acpm_chan *achan)
 
 /**
  * acpm_free_mbox_chans() - free mailbox channels.
- * @acpm:	pointer to driver data.
+ * @data:	pointer to driver data.
  */
-static void acpm_free_mbox_chans(struct acpm_info *acpm)
+static void acpm_free_mbox_chans(void *data)
 {
+	struct acpm_info *acpm = data;
 	int i;
 
 	for (i = 0; i < acpm->num_chans; i++)
@@ -558,6 +559,10 @@ static int acpm_channels_init(struct acpm_info *acpm)
 	if (!acpm->chans)
 		return -ENOMEM;
 
+	ret = devm_add_action_or_reset(dev, acpm_free_mbox_chans, acpm);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add mbox free action.\n");
+
 	chans_shmem = acpm->sram_base + readl(&shmem->chans);
 
 	for (i = 0; i < acpm->num_chans; i++) {
@@ -579,10 +584,8 @@ static int acpm_channels_init(struct acpm_info *acpm)
 		cl->dev = dev;
 
 		achan->chan = mbox_request_channel(cl, 0);
-		if (IS_ERR(achan->chan)) {
-			acpm_free_mbox_chans(acpm);
+		if (IS_ERR(achan->chan))
 			return PTR_ERR(achan->chan);
-		}
 	}
 
 	return 0;

-- 
2.54.0.545.g6539524ca2-goog