[PATCH v4 phy-next 1/9] soc: fsl: guts: perform fsl_guts_init() error teardown in reverse order of setup

[Vladimir Oltean]

fsl_guts_init() is about to get much more complicated and the central
error handling procedure cannot scale in its current design, unless we
add a lot of "if" conditions to detect what has been allocated and what
hasn't.

Currently the code relies on the fact that kfree(NULL) is safe, but this
doesn't scale to the case where "soc_dev_attr" itself is NULL, because
this would dereference "soc_dev_attr->family" and friends of a NULL
pointer.

Convert to the more typical error handling pattern where the teardown is
in the strict reverse order of setup, and a teardown step is only called
if its corresponding setup step was executed.

At the same time, maintain the optionality of soc_dev_attr->serial_number
by not checking whether that kasprintf() has returned NULL. In the error
path, kfree(NULL) is safe, so we don't need to add an "if" condition for
it. Michael Walle has confirmed that ignoring the error was intentional,
and we preserve that:
https://lore.kernel.org/linux-phy/DK44809N7Y8I.J2Z3U4N32H0Q@xxxxxxxxxx/

Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
v3->v4: patch is new
---
 drivers/soc/fsl/guts.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/drivers/soc/fsl/guts.c b/drivers/soc/fsl/guts.c
index 9bee7baec2b9..453456f31800 100644
--- a/drivers/soc/fsl/guts.c
+++ b/drivers/soc/fsl/guts.c
@@ -227,17 +227,23 @@ static int __init fsl_guts_init(void)
 	} else {
 		soc_dev_attr->family = kasprintf(GFP_KERNEL, "QorIQ");
 	}
-	if (!soc_dev_attr->family)
-		goto err_nomem;
+	if (!soc_dev_attr->family) {
+		ret = -ENOMEM;
+		goto err_free_soc_dev_attr;
+	}
 
 	soc_dev_attr->soc_id = kasprintf(GFP_KERNEL, "svr:0x%08x", svr);
-	if (!soc_dev_attr->soc_id)
-		goto err_nomem;
+	if (!soc_dev_attr->soc_id) {
+		ret = -ENOMEM;
+		goto err_free_family;
+	}
 
 	soc_dev_attr->revision = kasprintf(GFP_KERNEL, "%d.%d",
 					   (svr >>  4) & 0xf, svr & 0xf);
-	if (!soc_dev_attr->revision)
-		goto err_nomem;
+	if (!soc_dev_attr->revision) {
+		ret = -ENOMEM;
+		goto err_free_soc_id;
+	}
 
 	if (soc_data)
 		soc_uid = fsl_guts_get_soc_uid(soc_data->sfp_compat,
@@ -249,7 +255,7 @@ static int __init fsl_guts_init(void)
 	soc_dev = soc_device_register(soc_dev_attr);
 	if (IS_ERR(soc_dev)) {
 		ret = PTR_ERR(soc_dev);
-		goto err;
+		goto err_free_serial_number;
 	}
 
 	pr_info("Machine: %s\n", soc_dev_attr->machine);
@@ -259,13 +265,14 @@ static int __init fsl_guts_init(void)
 
 	return 0;
 
-err_nomem:
-	ret = -ENOMEM;
-err:
-	kfree(soc_dev_attr->family);
-	kfree(soc_dev_attr->soc_id);
-	kfree(soc_dev_attr->revision);
+err_free_serial_number:
 	kfree(soc_dev_attr->serial_number);
+	kfree(soc_dev_attr->revision);
+err_free_soc_id:
+	kfree(soc_dev_attr->soc_id);
+err_free_family:
+	kfree(soc_dev_attr->family);
+err_free_soc_dev_attr:
 	kfree(soc_dev_attr);
 
 	return ret;
-- 
2.34.1