linux-kernel - Re: [PATCH v3] overlayfs: fix uninitialized pointers with free attribute

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Message-ID: <CAOQ4uxhg-B6BnygENmC3Y-mWCy+B1j8Eb=9hXu34whUdTAz+JQ@mail.gmail.com>
Date: Fri, 21 Nov 2025 09:17:46 +0100
From: Amir Goldstein <amir73il@...il.com>
To: Christian Brauner <brauner@...nel.org>
Cc: Miklos Szeredi <miklos@...redi.hu>, linux-unionfs@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Dan Carpenter <dan.carpenter@...aro.org>, 
	Ally Heev <allyheev@...il.com>
Subject: Re: [PATCH v3] overlayfs: fix uninitialized pointers with free attribute

On Fri, Nov 21, 2025 at 8:51 AM Ally Heev <allyheev@...il.com> wrote:
>
> Uninitialized pointers with `__free` attribute can cause undefined
> behavior as the memory assigned randomly to the pointer is freed
> automatically when the pointer goes out of scope.
>
> overlayfs doesn't have any bugs related to this as of now, but
> it is better to initialize and assign pointers with `__free` attribute
> in one statement to ensure proper scope-based cleanup
>
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
> Acked-by: Amir Goldstein <amir73il@...il.com>
> Signed-off-by: Ally Heev <allyheev@...il.com>
> ---

Christian,

If you agree with this fix, please apply to vfs-6.19.ovl.

Please note that the fix patch at the tip of vfs-6.19.ovl is missing your S-O-B.

Thanks,
Amir.

> Changes in v3:
> - reverted to v1
> - Link to v2: https://lore.kernel.org/r/20251115-aheev-uninitialized-free-attr-overlayfs-v2-1-815a48767340@gmail.com
>
> Changes in v2:
> - moved the variable initialization to the top
> - Link to v1: https://lore.kernel.org/r/20251105-aheev-uninitialized-free-attr-overlayfs-v1-1-6ae4624655db@gmail.com
> ---
>  fs/overlayfs/params.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
> index 63b7346c5ee1c127a9c33b12c3704aa035ff88cf..59445b53b5b88893ef7923128da99cd1934bdc6c 100644
> --- a/fs/overlayfs/params.c
> +++ b/fs/overlayfs/params.c
> @@ -448,10 +448,10 @@ static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
>                 err = ovl_do_parse_layer(fc, param->string, &layer_path, layer);
>                 break;
>         case fs_value_is_file: {
> -               char *buf __free(kfree);
>                 char *layer_name;
>
> -               buf = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);
> +               char *buf __free(kfree) = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);
> +
>                 if (!buf)
>                         return -ENOMEM;
>
>
> ---
> base-commit: c9cfc122f03711a5124b4aafab3211cf4d35a2ac
> change-id: 20251105-aheev-uninitialized-free-attr-overlayfs-6873964429e0
>
> Best regards,
> --
> Ally Heev <allyheev@...il.com>
>