Commit 01da5216 authored by Ally Heev's avatar Ally Heev Committed by Andrew Morton
Browse files

checkpatch: add uninitialized pointer with __free attribute check 

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

Link: https://lkml.kernel.org/r/20251203-aheev-checkpatch-uninitialized-free-v7-1-841e3b31d8f3@gmail.com


Signed-off-by: default avatarAlly Heev <allyheev@gmail.com>
Suggested-by: default avatarDan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/all/8a4c0b43-cf63-400d-b33d-d9c447b7e0b9@suswa.mountain/
Link: https://lore.kernel.org/all/58fd478f408a34b578ee8d949c5c4b4da4d4f41d.camel@HansenPartnership.com/


Acked-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarKrzysztof Kozlowski <krzk@kernel.org>
Acked-by: default avatarJoe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: David Hunter <david.hunter.linux@gmail.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: James Bottomley <james.bottomley@HansenPartnership.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Menon, Nishanth <nm@ti.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Viresh Kumar <vireshk@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e6b4d264

Documentation/dev-tools/checkpatch.rst

+23 −0
Original line number Diff line number Diff line
@@ -1009,6 +1009,29 @@ Functions and Variables 


      return bar;



  **UNINITIALIZED_PTR_WITH_FREE**

    Pointers with __free attribute should be declared at the place of use

    and initialized (see include/linux/cleanup.h). In this case

    declarations at the top of the function rule can be relaxed. Not doing

    so may lead to undefined behavior as the memory assigned (garbage,

    in case not initialized) to the pointer is freed automatically when

    the pointer goes out of scope.



    Also see: https://lore.kernel.org/lkml/58fd478f408a34b578ee8d949c5c4b4da4d4f41d.camel@HansenPartnership.com/



    Example::



      type var __free(free_func);

      ... // var not used, but, in future someone might add a return here

      var = malloc(var_size);

      ...



    should be initialized as::



      ...

      type var __free(free_func) = malloc(var_size);

      ...





Permissions

-----------

scripts/checkpatch.pl

+6 −0
Original line number Diff line number Diff line
@@ -7732,6 +7732,12 @@ 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+__free\s*\(\s*$Ident\s*\)\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