[PATCH v2 1/2] checkpatch: add uninitialized pointer with __free attribute check

[Ally Heev]

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@xxxxxxxxxx>
Link: https://lore.kernel.org/all/8a4c0b43-cf63-400d-b33d-d9c447b7e0b9@suswa.mountain/
Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Ally Heev <allyheev@xxxxxxxxx>
---
 Documentation/dev-tools/checkpatch.rst | 5 +++++
 scripts/checkpatch.pl                  | 7 +++++++
 2 files changed, 12 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..1009a4a065e910143dabeee6640b3b3a4bd3fe06 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -509,6 +509,7 @@ our $InitAttributeData = qr{$InitAttributePrefix(?:initdata\b)};
 our $InitAttributeConst = qr{$InitAttributePrefix(?:initconst\b)};
 our $InitAttributeInit = qr{$InitAttributePrefix(?:init\b)};
 our $InitAttribute = qr{$InitAttributeData|$InitAttributeConst|$InitAttributeInit};
+our $FreeAttribute = qr{__free\s*\(\s*$Ident\s*\)};
 
 # Notes to $Attribute:
 # We need \b after 'init' otherwise 'initconst' will cause a false positive in a check
@@ -7721,6 +7722,12 @@ sub process {
 				ERROR("MISSING_SENTINEL", "missing sentinel in ID array\n" . "$here\n$stat\n");
 			}
 		}
+
+# check for uninitialized pointers with __free attribute
+		while ($line =~ /\*\s*($Ident)\s+$FreeAttribute\s*[,;]/g) {
+			ERROR("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

-- 
2.47.3