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    Subject[PATCH 5.4 041/309] usb: gadget: f_fs: set req->num_sgs as 0 for non-sg transfer
    Date
    From: Peter Chen <peter.chen@nxp.com>

    commit d2450c6937018d40d4111fe830fa48d4ddceb8d0 upstream.

    The UDC core uses req->num_sgs to judge if scatter buffer list is used.
    Eg: usb_gadget_map_request_by_dev. For f_fs sync io mode, the request
    is re-used for each request, so if the 1st request->length > PAGE_SIZE,
    and the 2nd request->length is <= PAGE_SIZE, the f_fs uses the 1st
    req->num_sgs for the 2nd request, it causes the UDC core get the wrong
    req->num_sgs value (The 2nd request doesn't use sg). For f_fs async
    io mode, it is not harm to initialize req->num_sgs as 0 either, in case,
    the UDC driver doesn't zeroed request structure.

    Cc: Jun Li <jun.li@nxp.com>
    Cc: stable <stable@vger.kernel.org>
    Fixes: 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather buffers")
    Signed-off-by: Peter Chen <peter.chen@nxp.com>
    Signed-off-by: Felipe Balbi <balbi@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/usb/gadget/function/f_fs.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/usb/gadget/function/f_fs.c
    +++ b/drivers/usb/gadget/function/f_fs.c
    @@ -1062,6 +1062,7 @@ static ssize_t ffs_epfile_io(struct file
    req->num_sgs = io_data->sgt.nents;
    } else {
    req->buf = data;
    + req->num_sgs = 0;
    }
    req->length = data_len;

    @@ -1105,6 +1106,7 @@ static ssize_t ffs_epfile_io(struct file
    req->num_sgs = io_data->sgt.nents;
    } else {
    req->buf = data;
    + req->num_sgs = 0;
    }
    req->length = data_len;


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