On Tue, Jan 05, 2010 at 01:44:25PM -0800, Brandeburg, Jesse wrote: > Neil, I couple of comments below, I was just looking at the implementation > of this for e1000e. > > On Mon, 28 Dec 2009, Neil Horman wrote: > > > Hey all- > > A security discussion was recently given: > > http://events.ccc.de/congress/2009/Fahrplan//events/3596.en.html > > And a patch that I submitted awhile back was brought up. Apparently some of > > their testing revealed that they were able to force a buffer fragment in > > e1000 > > in which the trailing fragment was greater than 4 bytes. As a result the > > fragment check I introduced failed to detect the fragement and a partial > > invalid > > frame was passed up into the network stack. I've written this patch to > > correct > > it. I'm in the process of testing it now, but it makes good logical sense > > to > > me. Effectively it maintains a per-adapter state variable which detects a > > non-EOP frame, and discards it and subsequent non-EOP frames leading up to > > _and_ > > _including_ the next positive-EOP frame (as it is by definition the last > > fragment). This should prevent any and all partial frames from entering the > > network stack from e1000 > > > > Regards > > Neil > > > > > > e1000.h | 3 ++- > > e1000_main.c | 14 ++++++++++++-- > > 2 files changed, 14 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/net/e1000/e1000.h b/drivers/net/e1000/e1000.h > > index 2a567df..3d421ab 100644 > > --- a/drivers/net/e1000/e1000.h > > +++ b/drivers/net/e1000/e1000.h > > @@ -331,7 +331,8 @@ struct e1000_adapter { > > enum e1000_state_t { > > __E1000_TESTING, > > __E1000_RESETTING, > > - __E1000_DOWN > > + __E1000_DOWN, > > + __E1000_DISCARDING > > }; > > > > extern char e1000_driver_name[]; > > diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c > > index 7e855f9..0731779 100644 > > --- a/drivers/net/e1000/e1000_main.c > > +++ b/drivers/net/e1000/e1000_main.c > > @@ -3850,16 +3850,26 @@ static bool e1000_clean_rx_irq(struct e1000_adapter > > *adapter, > > > > length = le16_to_cpu(rx_desc->length); > > /* !EOP means multiple descriptors were used to store a single > > - * packet, also make sure the frame isn't just CRC only */ > > - if (unlikely(!(status & E1000_RXD_STAT_EOP) || (length <= 4))) { > > + * packet, if thats the case we need to toss it. In fact, we > > + * to toss every packet with the EOP bit clear and the next > > + * frame that _does_ have the EOP bit set, as it is by > > + * definition only a frame fragment > > + */ > > + if (unlikely(!(status & E1000_RXD_STAT_EOP))) > > + set_bit(__E1000_DISCARDING, &adapter->flags); > > test_bit and set_bit and clear_bit are atomic operations, isn't that quite > a bit of overhead for something that is already being done in a guaranteed > single context? > > > + > > + if (test_bit(__E1000_DISCARDING, &adapter->flags)) { > > /* All receives must fit into a single buffer */ > > E1000_DBG("%s: Receive packet consumed multiple" > > " buffers\n", netdev->name); > > /* recycle */ > > buffer_info->skb = skb; > > + if (status & E1000_RXD_STAT_EOP) > > + clear_bit(__E1000_DISCARDING, &adapter->flags); > > couldn't these simply be read/modify/write assignments (aka |=) > > That would significantly avoid the extra cycles needed to implement three > atomic ops. > They certainly could be non-atomic assignments, but the other flags in the adapter falgs are atomic and I dont think its safe to mix and match the accesses, lest we get a waw race somewhere.
If you really think we need to save the save the cycles the best thing to probably do is define a new flags field separate from adapter->flags that can be accessed with non-atomics. Let me know if you would prefer that, and I'll happily re-spin the patch. Neil ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ E1000-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/e1000-devel
