linux-kernel - [PATCH] checkpatch: add uninitialized pointer with _

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Message-Id: <20251021-aheev-checkpatch-uninitialized-free-v1-1-18fb01bc6a7a@gmail.com>
Date: Tue, 21 Oct 2025 17:00:48 +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>, Ally Heev <allyheev@...il.com>
Subject: [PATCH] checkpatch: add uninitialized pointer with __free
 attribute check

uninitialized pointers with __free attribute can cause undefined
behaviour as the memory allocated to the pointer is freed
automatically when the pointer goes out of scope.
add check in checkpatch to detect such issues

Suggested-by: Dan Carpenter <dan.carpenter@...aro.org>
Link: https://lore.kernel.org/all/8a4c0b43-cf63-400d-b33d-d9c447b7e0b9@suswa.mountain/
Signed-off-by: Ally Heev <allyheev@...il.com>
---
Test:
ran checkpatch.pl before and after the change on 
crypto/asymmetric_keys/x509_public_key.c, which has
both initialized and uninitialized pointers
---
 Documentation/dev-tools/checkpatch.rst | 5 +++++
 scripts/checkpatch.pl                  | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index d5c47e560324fb2399a5b1bc99c891ed1de10535..1a304bf38bcd27e50bbb7cd4383b07ac54d20b0a 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -1009,6 +1009,11 @@ Functions and Variables
 
       return bar;
 
+  **UNINITIALIZED_PTR_WITH_FREE**
+    Pointers with __free attribute should be initialized. Not doing so
+    may lead to undefined behavior as the memory allocated (garbage,
+    in case not initialized) to the pointer is freed automatically
+    when the pointer goes out of scope.
 
 Permissions
 -----------
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 92669904eecc7a8d2afd3f2625528e02b6d17cd6..33cb09843431bebef72a4f5daab3a5d321bcb911 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -7721,6 +7721,12 @@ sub process {
 				ERROR("MISSING_SENTINEL", "missing sentinel in ID array\n" . "$here\n$stat\n");
 			}
 		}
+
+# check for uninitialized pointers with __free attribute
+		if ($line =~ /\s*$Type\s*($Ident)\s+__free\s*\(\s*$Ident\s*\)\s*;/) {
+			WARN("UNINITIALIZED_PTR_WITH_FREE",
+			      "pointer '$1' with __free attribute should be initialized\n" . $herecurr);
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on

---
base-commit: 6548d364a3e850326831799d7e3ea2d7bb97ba08
change-id: 20251021-aheev-checkpatch-uninitialized-free-5c39f75e10a1

Best regards,
-- 
Ally Heev <allyheev@...il.com>