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usb: gadget: return the right length in ffs_epfile_io()

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When the request length is aligned to maxpacketsize, sometimes
the return length ret > the user space requested len.

At that time, we will use min_t(size_t, ret, len) to limit the
size in case of user data buffer overflow.

But we need return the min_t(size_t, ret, len) to tell the user
space rightly also.

[ [email protected]: also fix comment's indentation ]

Acked-by: Michal Nazarewicz <[email protected]>
Reviewed-by: David Cohen <[email protected]>
Signed-off-by: Chuansheng Liu <[email protected]>
Signed-off-by: Felipe Balbi <[email protected]>
This commit is contained in:
Chuansheng Liu 2014-03-04 15:34:57 +08:00 • committed by Felipe Balbi
commit cfe919b53b
1 changed files with 15 additions and 13 deletions
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28
drivers/usb/gadget/f_fs.c
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@ -838,19 +838,21 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
ret = -EINTR;
usb_ep_dequeue(ep->ep, req);
} else {
/*
* XXX We may end up silently droping data here.
* Since data_len (i.e. req->length) may be bigger
* than len (after being rounded up to maxpacketsize),
* we may end up with more data then user space has
* space for.
*/
ret = ep->status;
if (io_data->read && ret > 0 &&
unlikely(copy_to_user(io_data->buf, data,
min_t(size_t, ret,
io_data->len))))
ret = -EFAULT;
/*
* XXX We may end up silently droping data
* here. Since data_len (i.e. req->length) may
* be bigger than len (after being rounded up
* to maxpacketsize), we may end up with more
* data then user space has space for.
*/
ret = ep->status;
if (io_data->read && ret > 0) {
ret = min_t(size_t, ret, io_data->len);
if (unlikely(copy_to_user(io_data->buf,
data, ret)))
ret = -EFAULT;
}
}
kfree(data);
}