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

[Tetsuo Handa]

Thank you. Please send to linux-next tree via apparmor tree, for
syzbot won't be able to test linux-next tree due to this build failure.

On 2026/07/15 21:14, Georgia Garcia wrote:
> 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)
>>  {
>