Re: [PATCH 07/23] vfs: Teach sendfile,splice,tee,and vmsplice to use file_hotplug_lock

[Eric W. Biederman]

Badari Pulavarty <pbadari@xxxxxxxxx> writes:

> On Mon, 2009-06-01 at 14:50 -0700, Eric W. Biederman wrote:
>> From: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxxx>
>> 
>> Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>
>> ---
>>  fs/read_write.c |   28 +++++++++----
>>  fs/splice.c     |  111 +++++++++++++++++++++++++++++++++++++-----------------
>>  2 files changed, 95 insertions(+), 44 deletions(-)
>> 
>> diff --git a/fs/read_write.c b/fs/read_write.c
>> index 718baea..c473d74 100644
>> --- a/fs/read_write.c
>> +++ b/fs/read_write.c
>> @@ -861,21 +861,24 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
>>  		goto out;
>>  	if (!(in_file->f_mode & FMODE_READ))
>>  		goto fput_in;
>> +	retval = -EIO;
>> +	if (!file_hotplug_read_trylock(in_file))
>> +		goto fput_in;
>>  	retval = -EINVAL;
>>  	in_inode = in_file->f_path.dentry->d_inode;
>>  	if (!in_inode)
>> -		goto fput_in;
>> +		goto unlock_in;
>>  	if (!in_file->f_op || !in_file->f_op->splice_read)
>> -		goto fput_in;
>> +		goto unlock_in;
>>  	retval = -ESPIPE;
>>  	if (!ppos)
>>  		ppos = &in_file->f_pos;
>>  	else
>>  		if (!(in_file->f_mode & FMODE_PREAD))
>> -			goto fput_in;
>> +			goto unlock_in;
>>  	retval = rw_verify_area(READ, in_file, ppos, count);
>>  	if (retval < 0)
>> -		goto fput_in;
>> +		goto unlock_in;
>>  	count = retval;
>>  
>>  	/*
>> @@ -884,16 +887,19 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
>>  	retval = -EBADF;
>>  	out_file = fget_light(out_fd, &fput_needed_out);
>>  	if (!out_file)
>> -		goto fput_in;
>> +		goto unlock_in;
>>  	if (!(out_file->f_mode & FMODE_WRITE))
>>  		goto fput_out;
>> +	retval = -EIO;
>> +	if (!file_hotplug_read_trylock(out_file))
>> +		goto fput_out;
>>  	retval = -EINVAL;
>>  	if (!out_file->f_op || !out_file->f_op->sendpage)
>> -		goto fput_out;
>> +		goto unlock_out;
>>  	out_inode = out_file->f_path.dentry->d_inode;
>>  	retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count);
>>  	if (retval < 0)
>> -		goto fput_out;
>> +		goto unlock_out;
>>  	count = retval;
>>  
>>  	if (!max)
>> @@ -902,11 +908,11 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
>>  	pos = *ppos;
>>  	retval = -EINVAL;
>>  	if (unlikely(pos < 0))
>> -		goto fput_out;
>> +		goto unlock_out;
>>  	if (unlikely(pos + count > max)) {
>>  		retval = -EOVERFLOW;
>>  		if (pos >= max)
>> -			goto fput_out;
>> +			goto unlock_out;
>>  		count = max - pos;
>>  	}
>>  
>> @@ -933,8 +939,12 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
>>  	if (*ppos > max)
>>  		retval = -EOVERFLOW;
>>  
>> +unlock_out:
>> +	file_hotplug_read_unlock(out_file);
>>  fput_out:
>>  	fput_light(out_file, fput_needed_out);
>> +unlock_in:
>> +	file_hotplug_read_unlock(in_file);
>>  fput_in:
>>  	fput_light(in_file, fput_needed_in);
>>  out:
>> diff --git a/fs/splice.c b/fs/splice.c
>> index 666953d..fc6b3a5 100644
>> --- a/fs/splice.c
>> +++ b/fs/splice.c
>> @@ -1464,15 +1464,21 @@ SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
>>  
>>  	error = -EBADF;
>>  	file = fget_light(fd, &fput);
>> -	if (file) {
>> -		if (file->f_mode & FMODE_WRITE)
>> -			error = vmsplice_to_pipe(file, iov, nr_segs, flags);
>> -		else if (file->f_mode & FMODE_READ)
>> -			error = vmsplice_to_user(file, iov, nr_segs, flags);
>> +	if (!file)
>> +		goto out;
>>  
>> -		fput_light(file, fput);
>> -	}
>> +	if (!file_hotplug_read_trylock(file))
>> +		goto fput_file;
>>  
>> +	if (file->f_mode & FMODE_WRITE)
>> +		error = vmsplice_to_pipe(file, iov, nr_segs, flags);
>> +	else if (file->f_mode & FMODE_READ)
>> +		error = vmsplice_to_user(file, iov, nr_segs, flags);
>> +
>> +	file_hotplug_read_unlock(file);
>> +fput_file:
>> +	fput_light(file, fput);
>> +out:
>>  	return error;
>>  }
>>  
>> @@ -1489,21 +1495,39 @@ SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
>>  
>>  	error = -EBADF;
>>  	in = fget_light(fd_in, &fput_in);
>> -	if (in) {
>> -		if (in->f_mode & FMODE_READ) {
>> -			out = fget_light(fd_out, &fput_out);
>> -			if (out) {
>> -				if (out->f_mode & FMODE_WRITE)
>> -					error = do_splice(in, off_in,
>> -							  out, off_out,
>> -							  len, flags);
>> -				fput_light(out, fput_out);
>> -			}
>> -		}
>> +	if (!in)
>> +		goto out;
>>  
>> -		fput_light(in, fput_in);
>> -	}
>> +	if (!(in->f_mode & FMODE_READ))
>> +		goto fput_in;
>> +
>> +	error = -EIO;
>> +	if (!file_hotplug_read_trylock(in))
>> +		goto fput_in;
>> +
>> +	error = -EBADF;
>> +	out = fget_light(fd_out, &fput_out);
>> +	if (!out)
>> +		goto unlock_in;
>> +
>> +	if (!(out->f_mode & FMODE_WRITE))
>> +		goto fput_out;
>> +
>> +	error = -EIO;
>> +	if (!file_hotplug_read_trylock(out))
>> +		goto fput_out;
>> +
>> +	error = do_splice(in, off_in, out, off_out, len, flags);
>>  
>> +	file_hotplug_read_unlock(out);
>> +fput_out:
>> +	fput_light(out, fput_out);
>> +unlock_in:
>> +	file_hotplug_read_unlock(in);
>> +fput_in:
>> +	fput_light(in, fput_in);
>> +
>> +out:
>>  	return error;
>>  }
>>  
>> @@ -1703,27 +1727,44 @@ static long do_tee(struct file *in, struct file *out, size_t len,
>>  
>>  SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
>>  {
>> -	struct file *in;
>> -	int error, fput_in;
>> +	struct file *in, *out;
>> +	int error, fput_in, fput_out;
>>  
>>  	if (unlikely(!len))
>>  		return 0;
>>  
>>  	error = -EBADF;
>>  	in = fget_light(fdin, &fput_in);
>> -	if (in) {
>> -		if (in->f_mode & FMODE_READ) {
>> -			int fput_out;
>> -			struct file *out = fget_light(fdout, &fput_out);
>> -
>> -			if (out) {
>> -				if (out->f_mode & FMODE_WRITE)
>> -					error = do_tee(in, out, len, flags);
>> -				fput_light(out, fput_out);
>> -			}
>> -		}
>> - 		fput_light(in, fput_in);
>> - 	}
>> +	if (!in)
>> +		goto out;
>> +
>> +	if (!(in->f_mode & FMODE_READ))
>> +		goto unlock_in;   <<<<<<<
>
> Shouldn't this be
> 		goto fput_in; 

Good point.  That is a bug.

> ? btw, its confusing to have labels and variables with same name:
> fput_in and fput_out. You may want to rename labels ?

Mayhap.  I didn't start that one, although I am clearly spreading
it around here.  Do you have a better naming suggestion?

>> +	error = -EIO;
>> +	if (!file_hotplug_read_trylock(in))
>> +		goto fput_in;
>> +
>> +	error = -EBADF;
>> +	out = fget_light(fdout, &fput_out);
>> +	if (!out)
>> +		goto unlock_in;
>> +
>> +	if (!(out->f_mode & FMODE_WRITE))
>> +		goto fput_out;
>> +
>> +	if (!file_hotplug_read_trylock(out))
>> +		goto fput_out;
>> +
>> +	error = do_tee(in, out, len, flags);
>> +
>> +	file_hotplug_read_unlock(out);
>> +fput_out:
>> +	fput_light(out, fput_out);
>> +unlock_in:
>> +	file_hotplug_read_unlock(in);
>> +fput_in:
>> +	fput_light(in, fput_in);
>> +out:
>>  	return error;
>>  }


Eric
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