[PATCH] apparmor: replace decompress_zstd() prototype with its entity

[Georgia Garcia]

Hello,

On Sun, 2026-07-12 at 19:17 +0900, Tetsuo Handa wrote:
> Fix "undefined symbol: decompress_zstd" error caused by decompress_zstd()
> being guarded by CONFIG_SECURITY_APPARMOR_EXPORT_BINARY=y.
> 

Acked-by: Georgia Garcia <georgia.garcia at canonical.com>

> Reported-by: syzbot+1f14a35d0c73d31555e4 at syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1f14a35d0c73d31555e4
> Fixes: 17b5758bf35c ("apparmor: Initial support for compressed policies")
> Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
> ---
>  security/apparmor/apparmorfs.c | 72 +++++++++++++++++-----------------
>  1 file changed, 36 insertions(+), 36 deletions(-)
> 
> diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
> index 2ae9ab94a5a91..152c7967ff1ba 100644
> --- a/security/apparmor/apparmorfs.c
> +++ b/security/apparmor/apparmorfs.c
> @@ -483,7 +483,42 @@ static struct aa_loaddata *aa_simple_write_to_buffer(const char __user *userbuf,
>  
>  	return data;
>  }
> -static int decompress_zstd(char *src, size_t slen, char *dst, size_t dlen);
> +
> +static int decompress_zstd(char *src, size_t slen, char *dst, size_t dlen)
> +{
> +	if (slen < dlen) {
> +		const size_t wksp_len = zstd_dctx_workspace_bound();
> +		zstd_dctx *ctx;
> +		void *wksp;
> +		size_t out_len;
> +		int ret = 0;
> +
> +		wksp = kvzalloc(wksp_len, GFP_KERNEL);
> +		if (!wksp) {
> +			ret = -ENOMEM;
> +			goto cleanup;
> +		}
> +		ctx = zstd_init_dctx(wksp, wksp_len);
> +		if (ctx == NULL) {
> +			ret = -ENOMEM;
> +			goto cleanup;
> +		}
> +		out_len = zstd_decompress_dctx(ctx, dst, dlen, src, slen);
> +		if (zstd_is_error(out_len)) {
> +			ret = -EINVAL;
> +			goto cleanup;
> +		}
> +cleanup:
> +		kvfree(wksp);
> +		return ret;
> +	}
> +
> +	if (dlen < slen)
> +		return -EINVAL;
> +	memcpy(dst, src, slen);
> +	return 0;
> +}
> +
>  /**
>   * aa_get_data_from_compressed - common routine for getting compressed policy
>   * from user and get both compressed and uncompressed version.
> @@ -1517,41 +1552,6 @@ SEQ_RAWDATA_FOPS(revision);
>  SEQ_RAWDATA_FOPS(hash);
>  SEQ_RAWDATA_FOPS(compressed_size);
>  
> -static int decompress_zstd(char *src, size_t slen, char *dst, size_t dlen)
> -{
> -	if (slen < dlen) {
> -		const size_t wksp_len = zstd_dctx_workspace_bound();
> -		zstd_dctx *ctx;
> -		void *wksp;
> -		size_t out_len;
> -		int ret = 0;
> -
> -		wksp = kvzalloc(wksp_len, GFP_KERNEL);
> -		if (!wksp) {
> -			ret = -ENOMEM;
> -			goto cleanup;
> -		}
> -		ctx = zstd_init_dctx(wksp, wksp_len);
> -		if (ctx == NULL) {
> -			ret = -ENOMEM;
> -			goto cleanup;
> -		}
> -		out_len = zstd_decompress_dctx(ctx, dst, dlen, src, slen);
> -		if (zstd_is_error(out_len)) {
> -			ret = -EINVAL;
> -			goto cleanup;
> -		}
> -cleanup:
> -		kvfree(wksp);
> -		return ret;
> -	}
> -
> -	if (dlen < slen)
> -		return -EINVAL;
> -	memcpy(dst, src, slen);
> -	return 0;
> -}
> -
>  static ssize_t rawdata_read(struct file *file, char __user *buf, size_t size,
>  			    loff_t *ppos)
>  {