linux-kernel - [PATCH v2 2/2] add check for pointers with _

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Message-Id: <20251024-aheev-checkpatch-uninitialized-free-v2-2-16c0900e8130@gmail.com>
Date: Fri, 24 Oct 2025 22:59:16 +0530
From: Ally Heev <allyheev@...il.com>
To: Dwaipayan Ray <dwaipayanray1@...il.com>, 
 Lukas Bulwahn <lukas.bulwahn@...il.com>, Joe Perches <joe@...ches.com>, 
 Jonathan Corbet <corbet@....net>, Andy Whitcroft <apw@...onical.com>
Cc: workflows@...r.kernel.org, linux-doc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Dan Carpenter <dan.carpenter@...aro.org>, 
 David Hunter <david.hunter.linux@...il.com>, 
 Shuah Khan <skhan@...uxfoundation.org>, Viresh Kumar <vireshk@...nel.org>, 
 Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>, 
 linux-pm <linux-pm@...r.kernel.org>, dan.j.williams@...el.com, 
 Ally Heev <allyheev@...il.com>
Subject: [PATCH v2 2/2] add check for pointers with __free attribute
 initialized to NULL

pointers with __free attribute initialized to NULL
pose potential cleanup issues [1] when a function uses
interdependent variables with cleanup attributes

Link: https://docs.kernel.org/core-api/cleanup.html [1]
Link: https://lore.kernel.org/all/68f7b830ec21a_10e910070@dwillia2-mobl4.notmuch/
Suggested-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Ally Heev <allyheev@...il.com>
---
 Documentation/dev-tools/checkpatch.rst | 6 ++++++
 scripts/checkpatch.pl                  | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index 1a304bf38bcd27e50bbb7cd4383b07ac54d20b0a..c39213b814f487290d2b0e5d320a4313ada9bbad 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -1015,6 +1015,12 @@ Functions and Variables
     in case not initialized) to the pointer is freed automatically
     when the pointer goes out of scope.
 
+  **NULL_INITIALIZED_PTR_WITH_FREE**
+    Pointers with __free attribute should not be initialized to NULL.
+    Always define and assign such pointers in one statement.
+
+    See: https://docs.kernel.org/core-api/cleanup.html
+
 Permissions
 -----------
 
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 1009a4a065e910143dabeee6640b3b3a4bd3fe06..cf186dafc191f1c39d01b3660f19101f6cc61a82 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -7728,6 +7728,12 @@ sub process {
 			ERROR("UNINITIALIZED_PTR_WITH_FREE",
 			      "pointer '$1' with __free attribute should be initialized\n" . $herecurr);
 		}
+
+# check for pointers with __free attribute initialized to NULL
+		while ($line =~ /\*\s*($Ident)\s+$FreeAttribute\s*=\s*NULL\b/g) {
+			WARN("NULL_INITIALIZED_PTR_WITH_FREE",
+			      "pointer '$1' with __free attribute should be initialized to a non-NULL address\n" . $herecurr);
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on

-- 
2.47.3