linux-kernel - Re: [PATCH 2/3] userfaultfd: convert to ->read

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Date: Wed, 3 Apr 2024 07:44:51 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] userfaultfd: convert to ->read_iter()

On 4/3/24 4:09 AM, Christian Brauner wrote:
>> @@ -2215,16 +2216,25 @@ static int new_userfaultfd(int flags)
>>  	init_rwsem(&ctx->map_changing_lock);
>>  	atomic_set(&ctx->mmap_changing, 0);
>>  	ctx->mm = current->mm;
>> -	/* prevent the mm struct to be freed */
>> -	mmgrab(ctx->mm);
>> +
>> +	fd = get_unused_fd_flags(O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS));
>> +	if (fd < 0)
>> +		goto err_out;
>>  
>>  	/* Create a new inode so that the LSM can block the creation.  */
>> -	fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
>> +	file = anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
>>  			O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);
>> -	if (fd < 0) {
>> -		mmdrop(ctx->mm);
>> -		kmem_cache_free(userfaultfd_ctx_cachep, ctx);
>> +	if (IS_ERR(file)) {
>> +		fd = PTR_ERR(file);
>> +		goto err_out;
> 
> You're leaking the fd you allocated above.

Oops yes - thanks, fixed.

-- 
Jens Axboe