| Date | Wed, 3 Dec 2008 11:48:18 -0800 | From | Greg KH <> | Subject | [patch 003/104] USB: usbmon: fix read(2) |
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2.6.27-stable review patch. If anyone has any objections, please let us know.
------------------ From: Pete Zaitcev <zaitcev@redhat.com>
commit f1c0a2a3aff53698f4855968d576464041d49b39 upstream.
There's a bug in the usbmon binary reader: When using read() to fetch the packets and a packet's data is partially read, the next read call will once again return up to len_cap bytes of data. The b_read counter is not regarded when determining the remaining chunk size.
So, when dumping USB data with "cat /dev/usbmon0 > usbmon.trace" while reading from a USB storage device and analyzing the dump file afterwards it will get out of sync after a couple of packets.
Signed-off-by: Ingo van Lil <inguin@gmx.de> Signed-off-by: Pete Zaitcev <zaitcev@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/usb/mon/mon_bin.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/usb/mon/mon_bin.c +++ b/drivers/usb/mon/mon_bin.c @@ -687,7 +687,10 @@ static ssize_t mon_bin_read(struct file } if (rp->b_read >= sizeof(struct mon_bin_hdr)) { - step_len = min(nbytes, (size_t)ep->len_cap); + step_len = ep->len_cap; + step_len -= rp->b_read - sizeof(struct mon_bin_hdr); + if (step_len > nbytes) + step_len = nbytes; offset = rp->b_out + PKT_SIZE; offset += rp->b_read - sizeof(struct mon_bin_hdr); if (offset >= rp->b_size)
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