> -----Original Message----- > From: Robert Sanford [mailto:rsanford2 at gmail.com] > Sent: Monday, March 28, 2016 9:52 PM > To: dev at dpdk.org; Dumitrescu, Cristian <cristian.dumitrescu at intel.com> > Subject: [PATCH 2/4] port: fix ring writer buffer overflow > > Ring writer tx_bulk functions may write past the end of tx_buf[]. > Solution is to double the size of tx_buf[]. > > Signed-off-by: Robert Sanford <rsanford at akamai.com> > --- > lib/librte_port/rte_port_ring.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/lib/librte_port/rte_port_ring.c b/lib/librte_port/rte_port_ring.c > index b847fea..765ecc5 100644 > --- a/lib/librte_port/rte_port_ring.c > +++ b/lib/librte_port/rte_port_ring.c > @@ -179,7 +179,7 @@ rte_port_ring_reader_stats_read(void *port, > struct rte_port_ring_writer { > struct rte_port_out_stats stats; > > - struct rte_mbuf *tx_buf[RTE_PORT_IN_BURST_SIZE_MAX]; > + struct rte_mbuf *tx_buf[2 * RTE_PORT_IN_BURST_SIZE_MAX]; > struct rte_ring *ring; > uint32_t tx_burst_sz; > uint32_t tx_buf_count; > @@ -447,7 +447,7 @@ rte_port_ring_writer_stats_read(void *port, > struct rte_port_ring_writer_nodrop { > struct rte_port_out_stats stats; > > - struct rte_mbuf *tx_buf[RTE_PORT_IN_BURST_SIZE_MAX]; > + struct rte_mbuf *tx_buf[2 * RTE_PORT_IN_BURST_SIZE_MAX]; > struct rte_ring *ring; > uint32_t tx_burst_sz; > uint32_t tx_buf_count; > -- > 1.7.1
Hi Robert, How is the buffer overflow taking place? After looking long and hard, I spotted that buffer overflow can potentially take place when the following conditions are met: 1. The input packet burst does not meet the conditions of (a) being contiguous (first n bits set in pkts_mask, all the other bits cleared) and (b) containing a full burst, i.e. at least tx_burst_sz packets (n >= tx_burst_size). This is the slow(er) code path taken when local variable expr != 0. 2. There are some packets already in the buffer. 3. The number of packets in the incoming burst (i.e. popcount(pkts_mask)) plus the number of packets already in the buffer exceeds the buffer size (RTE_PORT_IN_BURST_SIZE_MAX, i.e. 64). Is this the buffer overflow scenario that you detected? Thanks, Cristian