From: Florian Kauer florian.kauer@linutronix.de
[ Upstream commit ef27f655b438bed4c83680e4f01e1cde2739854b ]
When a frame can not be transmitted in XDP_REDIRECT (e.g. due to a full queue), it is necessary to free it by calling xdp_return_frame_rx_napi.
However, this is the responsibility of the caller of the ndo_xdp_xmit (see for example bq_xmit_all in kernel/bpf/devmap.c) and thus calling it inside igc_xdp_xmit (which is the ndo_xdp_xmit of the igc driver) as well will lead to memory corruption.
In fact, bq_xmit_all expects that it can return all frames after the last successfully transmitted one. Therefore, break for the first not transmitted frame, but do not call xdp_return_frame_rx_napi in igc_xdp_xmit. This is equally implemented in other Intel drivers such as the igb.
There are two alternatives to this that were rejected: 1. Return num_frames as all the frames would have been transmitted and release them inside igc_xdp_xmit. While it might work technically, it is not what the return value is meant to represent (i.e. the number of SUCCESSFULLY transmitted packets). 2. Rework kernel/bpf/devmap.c and all drivers to support non-consecutively dropped packets. Besides being complex, it likely has a negative performance impact without a significant gain since it is anyway unlikely that the next frame can be transmitted if the previous one was dropped.
The memory corruption can be reproduced with the following script which leads to a kernel panic after a few seconds. It basically generates more traffic than a i225 NIC can transmit and pushes it via XDP_REDIRECT from a virtual interface to the physical interface where frames get dropped.
#!/bin/bash INTERFACE=enp4s0 INTERFACE_IDX=`cat /sys/class/net/$INTERFACE/ifindex`
sudo ip link add dev veth1 type veth peer name veth2 sudo ip link set up $INTERFACE sudo ip link set up veth1 sudo ip link set up veth2
cat << EOF > redirect.bpf.c
SEC("prog") int redirect(struct xdp_md *ctx) { return bpf_redirect($INTERFACE_IDX, 0); }
char _license[] SEC("license") = "GPL"; EOF clang -O2 -g -Wall -target bpf -c redirect.bpf.c -o redirect.bpf.o sudo ip link set veth2 xdp obj redirect.bpf.o
cat << EOF > pass.bpf.c
SEC("prog") int pass(struct xdp_md *ctx) { return XDP_PASS; }
char _license[] SEC("license") = "GPL"; EOF clang -O2 -g -Wall -target bpf -c pass.bpf.c -o pass.bpf.o sudo ip link set $INTERFACE xdp obj pass.bpf.o
cat << EOF > trafgen.cfg
{ /* Ethernet Header */ 0xe8, 0x6a, 0x64, 0x41, 0xbf, 0x46, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, const16(ETH_P_IP),
/* IPv4 Header */ 0b01000101, 0, # IPv4 version, IHL, TOS const16(1028), # IPv4 total length (UDP length + 20 bytes (IP header)) const16(2), # IPv4 ident 0b01000000, 0, # IPv4 flags, fragmentation off 64, # IPv4 TTL 17, # Protocol UDP csumip(14, 33), # IPv4 checksum
/* UDP Header */ 10, 0, 1, 1, # IP Src - adapt as needed 10, 0, 1, 2, # IP Dest - adapt as needed const16(6666), # UDP Src Port const16(6666), # UDP Dest Port const16(1008), # UDP length (UDP header 8 bytes + payload length) csumudp(14, 34), # UDP checksum
/* Payload */ fill('W', 1000), } EOF
sudo trafgen -i trafgen.cfg -b3000MB -o veth1 --cpp
Fixes: 4ff320361092 ("igc: Add support for XDP_REDIRECT action") Signed-off-by: Florian Kauer florian.kauer@linutronix.de Reviewed-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Tested-by: Naama Meir naamax.meir@linux.intel.com Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/igc/igc_main.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c index 98de34d0ce07e..e549ffca88e39 100644 --- a/drivers/net/ethernet/intel/igc/igc_main.c +++ b/drivers/net/ethernet/intel/igc/igc_main.c @@ -6489,7 +6489,7 @@ static int igc_xdp_xmit(struct net_device *dev, int num_frames, int cpu = smp_processor_id(); struct netdev_queue *nq; struct igc_ring *ring; - int i, drops; + int i, nxmit;
if (unlikely(!netif_carrier_ok(dev))) return -ENETDOWN; @@ -6505,16 +6505,15 @@ static int igc_xdp_xmit(struct net_device *dev, int num_frames, /* Avoid transmit queue timeout since we share it with the slow path */ txq_trans_cond_update(nq);
- drops = 0; + nxmit = 0; for (i = 0; i < num_frames; i++) { int err; struct xdp_frame *xdpf = frames[i];
err = igc_xdp_init_tx_descriptor(ring, xdpf); - if (err) { - xdp_return_frame_rx_napi(xdpf); - drops++; - } + if (err) + break; + nxmit++; }
if (flags & XDP_XMIT_FLUSH) @@ -6522,7 +6521,7 @@ static int igc_xdp_xmit(struct net_device *dev, int num_frames,
__netif_tx_unlock(nq);
- return num_frames - drops; + return nxmit; }
static void igc_trigger_rxtxq_interrupt(struct igc_adapter *adapter,