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@linaro.org>
Closes: https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
Acked-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Ally Heev <allyheev@gmail.com>
---
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@gmail.com>

On Fri, Nov 21, 2025 at 8:51 AM Ally Heev <allyheev@gmail.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@linaro.org>
> Closes: https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
> Acked-by: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Ally Heev <allyheev@gmail.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@gmail.com>
>