Re: [RFC][PATCH 4/4] pstore: Replace classic kmalloc code pattern with typed argument

Przemek Kitszel
2024-07-09T07:07:15Z

On 7/8/24 21:18, Kees Cook wrote:
> Using a short Coccinelle script, it is possible to replace the classic
> kmalloc code patterns with the typed information:
>
> @alloc@
> type TYPE;
> TYPE *P;
> expression GFP;
> identifier ALLOC =~ "k[mz]alloc";
> @@
>
> P = ALLOC(
> - \(sizeof(*P)\|sizeof(TYPE)\), GFP)
> + P, GFP)
>
> Show this just for kmalloc/kzalloc usage in fs/pstore as an example.
>
> Doing this for all allocator calls in the kernel touches much more:
>
> 11941 files changed, 22459 insertions(+), 22345 deletions(-)
>
> And obviously requires some more wrappers for kv*alloc, devm_*alloc,
> etc.
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
> Cc: linux-hardening@vger.kernel.org
> ---
> fs/pstore/blk.c | 2 +-
> fs/pstore/platform.c | 2 +-
> fs/pstore/ram.c | 3 +--
> fs/pstore/ram_core.c | 2 +-
> fs/pstore/zone.c | 2 +-
> 5 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
> index de8cf5d75f34..7bb9cacb380f 100644
> --- a/fs/pstore/blk.c
> +++ b/fs/pstore/blk.c
> @@ -297,7 +297,7 @@ static int __init __best_effort_init(void)
> return -EINVAL;
> }
>
> - best_effort_dev = kzalloc(sizeof(*best_effort_dev), GFP_KERNEL);
> + best_effort_dev = kzalloc(best_effort_dev, GFP_KERNEL);
> if (!best_effort_dev)
> return -ENOMEM;
I expect raised eyebrows and typical vocalizations of amusement :D -
IOW: we should consider changing the name of the macro, although I like
it as is :)

other:
you repeat the pointer name twice, and code is magic anyway, so perhaps:
kzalloc_me(best_effort_dev, GFP_KERNEL);
and another variant to cover declaration-with-init.