I can't confirm that this is 100% the same issue since the backtrace isn't identical, but I was able to hit the following panic on trusty's 3.13 just by running iperf to another system for a few hours:

[ 2613.269450] BUG: Bad page state in process iperf  pfn:41d5c57                
[ 2613.275172] page:ffffffbce66c3308 count:-1 mapcount:0 mapping:          (nul0
[ 2613.283219] page flags: 0x4000000000000000()                                 
[ 2613.288129] skbuff: skb_over_panic: text:ffffffbffc00a3d0 len:2994 put:1514 >
[ 2613.301642] Kernel panic - not syncing: BUG!                                 
[ 2613.305892] CPU: 0 PID: 1499 Comm: iperf Tainted: G    B         3.13.0-55-gu
[ 2613.314370] Call trace:                                                      
[ 2613.316805] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2613.322175] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2613.327199] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2613.332223] [<ffffffc000606984>] panic+0xe0/0x20c                            
[ 2613.336901] [<ffffffc00060dad4>] skb_panic+0x78/0x7c                         
[ 2613.341839] [<ffffffc000510b5c>] skb_put+0x88/0x8c                           
[ 2613.346610] [<ffffffbffc00a3cc>] xgene_enet_process_ring+0xdc/0x388 [xgene_e]
[ 2613.353967] [<ffffffbffc00a798>] xgene_enet_napi+0x1c/0x50 [xgene_enet]      
[ 2613.360546] [<ffffffc00051f8c8>] net_rx_action+0x15c/0x240                   
[ 2613.366002] [<ffffffc0000aae24>] __do_softirq+0x124/0x29c                    
[ 2613.371372] [<ffffffc0000ab29c>] irq_exit+0x8c/0xc0                          
[ 2613.376223] [<ffffffc0000850ac>] handle_IRQ+0x5c/0xc8                        
[ 2613.381248] [<ffffffc000081290>] gic_handle_irq+0x38/0x7c                    
[ 2613.386618] Exception stack(0xffffffc1ee3db7d0 to 0xffffffc1ee3db8f0)        
[ 2613.393025] b7c0:                                     e8204200 ffffffc1 fff81
[ 2613.401159] b7e0: ee3db910 ffffffc1 0060ec5c ffffffc0 00007964 00000000 ee3d1
[ 2613.409293] b800: 00000000 00000000 00000002 00000000 00000000 00000000 00000
[ 2613.417429] b820: 00000001 00000000 fff833d8 ffffffc1 fff833b0 ffffffc1 f0ce1
[ 2613.425563] b840: 00000000 00000000 00000001 00000000 00000000 00000000 00000
[ 2613.433697] b860: 00000000 00000000 000005a8 00000000 00000014 00000000 a4250
[ 2613.441831] b880: 00000000 00000000 e8204200 ffffffc1 fff83340 ffffffc1 e8201
[ 2613.449965] b8a0: ee3d8000 ffffffc1 008ec340 ffffffc0 009d7000 ffffffc0 e8201
[ 2613.458099] b8c0: 008ec340 ffffffc0 ff697000 00000001 008ec340 ffffffc0 ee3d1
[ 2613.466232] b8e0: 0060e6e0 ffffffc0 ee3db910 ffffffc1                        
[ 2613.471257] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2613.476023] [<ffffffc00060ed1c>] schedule+0x24/0x78                          
[ 2613.480875] [<ffffffc00060e040>] schedule_timeout+0x180/0x248                
[ 2613.486590] [<ffffffc00050a78c>] sk_wait_data+0xcc/0xd8                      
[ 2613.491788] [<ffffffc0005645ac>] tcp_recvmsg+0x59c/0x9f4                     
[ 2613.497072] [<ffffffc00058a038>] inet_recvmsg+0x48/0x90                      
[ 2613.502269] [<ffffffc0005057cc>] sock_recvmsg+0xa4/0xc8                      
[ 2613.507467] [<ffffffc000507878>] SyS_recvfrom+0xa0/0x100                     
[ 2613.512752] CPU4: stopping                                                   
[ 2613.515447] CPU: 4 PID: 0 Comm: swapper/4 Tainted: G    B         3.13.0-55-u
[ 2613.524012] Call trace:                                                      
[ 2613.526448] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2613.531819] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2613.536843] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2613.541868] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2613.547064] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2613.552433] Exception stack(0xffffffc1f3d4fe20 to 0xffffffc1f3d4ff40)        
[ 2613.558840] fe20: f3d4c000 ffffffc1 f3d4c000 ffffffc1 f3d4ff60 ffffffc1 00080
[ 2613.566975] fe40: 0000dda0 00000000 00000000 00000000 fffac834 ffffffc1 00031
[ 2613.575109] fe60: 00000008 00000000 00000010 00000000 42e30180 000002a6 ee321
[ 2613.583245] fe80: f3d41b10 ffffffc1 f3d4fd60 ffffffc1 00038659 00000001 00000
[ 2613.591379] fea0: 968741d0 0000007f e8000000 00000003 a7fd5bf4 0000007f c1a37
[ 2613.599513] fec0: 001f4210 ffffffc0 a83a16c0 0000007f fffffffb ffffffff f3d41
[ 2613.607648] fee0: f3d4c000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2613.615782] ff00: f3d4c000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2613.623916] ff20: 0061dd98 ffffffc0 f3d4ff60 ffffffc1 000855fc ffffffc0 f3d41
[ 2613.632050] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2613.636816] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2613.642619] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108           
[ 2613.648767] CPU3: stopping                                                   
[ 2613.651462] CPU: 3 PID: 0 Comm: swapper/3 Tainted: G    B         3.13.0-55-u
[ 2613.660027] Call trace:                                                      
[ 2613.662463] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2613.667833] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2613.672858] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2613.677882] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2613.683078] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2613.688448] Exception stack(0xffffffc1f3d4be20 to 0xffffffc1f3d4bf40)        
[ 2613.694855] be20: f3d48000 ffffffc1 f3d48000 ffffffc1 f3d4bf60 ffffffc1 00080
[ 2613.702989] be40: 0000d210 00000000 00000000 00000000 fffa1834 ffffffc1 00031
[ 2613.711125] be60: 00000020 00000000 0218b33c 13e894ee fffa1540 ffffffc1 00000
[ 2613.719259] be80: f3d41010 ffffffc1 f3d4bd60 ffffffc1 00000400 00000000 00000
[ 2613.727393] bea0: 988741d0 0000007f e8000000 00000003 a7fd51a4 0000007f c1a37
[ 2613.735528] bec0: 001f4210 ffffffc0 a83a16c0 0000007f fffffffb ffffffff f3d41
[ 2613.743663] bee0: f3d48000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2613.751797] bf00: f3d48000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2613.759932] bf20: 0061dd98 ffffffc0 f3d4bf60 ffffffc1 000855fc ffffffc0 f3d41
[ 2613.768067] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2613.772832] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2613.778634] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108           
[ 2613.784781] CPU2: stopping                                                   
[ 2613.787474] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G    B         3.13.0-55-u
[ 2613.796040] Call trace:                                                      
[ 2613.798474] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2613.803845] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2613.808869] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2613.813893] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2613.819089] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2613.824458] Exception stack(0xffffffc1f3d3fe20 to 0xffffffc1f3d3ff40)        
[ 2613.830865] fe20: f3d3c000 ffffffc1 f3d3c000 ffffffc1 f3d3ff60 ffffffc1 00080
[ 2613.839000] fe40: 0017d906 00000000 00000000 00000000 fff96834 ffffffc1 00031
[ 2613.847134] fe60: 00909e80 ffffffc0 00000010 00000000 127e7180 0000026c f1641
[ 2613.855268] fe80: f3d40510 ffffffc1 f3d3fd60 ffffffc1 00038601 00000001 00000
[ 2613.863402] fea0: 6a88c6a0 00000055 ffffffff 00000000 00000065 00000000 61742
[ 2613.871537] fec0: 001ef6ac ffffffc0 7bb9b82c 0000007f 00000074 00000000 f3d31
[ 2613.879671] fee0: f3d3c000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2613.887805] ff00: f3d3c000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2613.895939] ff20: 0061dd98 ffffffc0 f3d3ff60 ffffffc1 000855fc ffffffc0 f3d31
[ 2613.904072] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2613.908837] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2613.914639] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108           
[ 2613.920786] CPU5: stopping                                                   
[ 2613.923479] CPU: 5 PID: 0 Comm: swapper/5 Tainted: G    B         3.13.0-55-u
[ 2613.932045] Call trace:                                                      
[ 2613.934479] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2613.939849] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2613.944874] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2613.949898] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2613.955094] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2613.960463] Exception stack(0xffffffc1f3d53e20 to 0xffffffc1f3d53f40)        
[ 2613.966870] 3e20: f3d50000 ffffffc1 f3d50000 ffffffc1 f3d53f60 ffffffc1 00080
[ 2613.975004] 3e40: 00024d44 00000000 00000000 00000000 fffb7834 ffffffc1 00031
[ 2613.983140] 3e60: 00000000 00000000 e803be28 ffffffc1 8286fa80 00000260 fffb1
[ 2613.991274] 3e80: f3d42610 ffffffc1 f3d53d60 ffffffc1 0003877b 00000001 00000
[ 2613.999408] 3ea0: 950741d0 0000007f e8000000 00000003 a7fd5bf4 0000007f c1a37
[ 2614.007544] 3ec0: 001f4210 ffffffc0 a83a16c0 0000007f fffffffb ffffffff f3d51
[ 2614.015678] 3ee0: f3d50000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2614.023812] 3f00: f3d50000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2614.031946] 3f20: 0061dd98 ffffffc0 f3d53f60 ffffffc1 000855fc ffffffc0 f3d51
[ 2614.040079] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2614.044844] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2614.050646] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108           
[ 2614.056794] CPU6: stopping                                                   
[ 2614.059488] CPU: 6 PID: 0 Comm: swapper/6 Tainted: G    B         3.13.0-55-u
[ 2614.068054] Call trace:                                                      
[ 2614.070489] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2614.075860] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2614.080884] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2614.085909] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2614.091106] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2614.096475] Exception stack(0xffffffc1f3d57e20 to 0xffffffc1f3d57f40)        
[ 2614.102883] 7e20: f3d54000 ffffffc1 f3d54000 ffffffc1 f3d57f60 ffffffc1 00080
[ 2614.111019] 7e40: 00103e46 00000000 00000000 00000000 fffc2834 ffffffc1 00031
[ 2614.119154] 7e60: 00000008 00000000 00000010 00000000 7a2ebf80 00000260 df8c1
[ 2614.127288] 7e80: f3d43110 ffffffc1 f3d57d60 ffffffc1 00037747 00000001 00000
[ 2614.135423] 7ea0: 00000020 00000000 00000000 00000001 9b84ce50 0000007f 00000
[ 2614.143557] 7ec0: 000cb6b0 ffffffc0 9c1b3918 0000007f 00000000 00000000 f3d51
[ 2614.151691] 7ee0: f3d54000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2614.159825] 7f00: f3d54000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2614.167959] 7f20: 0061dd98 ffffffc0 f3d57f60 ffffffc1 000855fc ffffffc0 f3d51
[ 2614.176095] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2614.180860] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2614.186662] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108           
[ 2614.192808] CPU7: stopping                                                   
[ 2614.195501] CPU: 7 PID: 0 Comm: swapper/7 Tainted: G    B         3.13.0-55-u
[ 2614.204066] Call trace:                                                      
[ 2614.206500] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2614.211871] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2614.216895] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2614.221919] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2614.227115] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2614.232484] Exception stack(0xffffffc1f3d5be20 to 0xffffffc1f3d5bf40)        
[ 2614.238891] be20: f3d58000 ffffffc1 f3d58000 ffffffc1 f3d5bf60 ffffffc1 00080
[ 2614.247025] be40: 00003f02 00000000 00000000 00000000 fffcd834 ffffffc1 00031
[ 2614.255159] be60: 00000020 00000000 00000000 00000000 fffcd540 ffffffc1 fff81
[ 2614.263293] be80: f3d43c10 ffffffc1 f3d5bd60 ffffffc1 00000400 00000000 00000
[ 2614.271427] bea0: 01010101 01010101 ffffffff ffffffff ffffffff ffffffff 00000
[ 2614.279561] bec0: 001af300 ffffffc0 87577a90 0000007f 00000000 00000000 f3d51
[ 2614.287695] bee0: f3d58000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2614.295829] bf00: f3d58000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2614.303964] bf20: 0061dd98 ffffffc0 f3d5bf60 ffffffc1 000855fc ffffffc0 f3d51
[ 2614.312099] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2614.316864] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2614.322666] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108           
[ 2614.328814] CPU1: stopping                                                   
[ 2614.331508] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G    B         3.13.0-55-u
[ 2614.340074] Call trace:                                                      
[ 2614.342508] [<ffffffc00008848c>] dump_backtrace+0x0/0x16c                    
[ 2614.347879] [<ffffffc000088608>] show_stack+0x10/0x1c                        
[ 2614.352903] [<ffffffc00060c750>] dump_stack+0x74/0x94                        
[ 2614.357927] [<ffffffc00008ed3c>] handle_IPI+0x120/0x138                      
[ 2614.363124] [<ffffffc0000812cc>] gic_handle_irq+0x74/0x7c                    
[ 2614.368494] Exception stack(0xffffffc1f3d3be20 to 0xffffffc1f3d3bf40)        
[ 2614.374900] be20: f3d38000 ffffffc1 f3d38000 ffffffc1 f3d3bf60 ffffffc1 00080
[ 2614.383035] be40: 00026d10 00000000 00000000 00000000 fff8b834 ffffffc1 00031
[ 2614.391170] be60: 00000000 00000000 e8227868 ffffffc1 7ef37380 00000260 fff81
[ 2614.399304] be80: f3cd7310 ffffffc1 f3d3bd60 ffffffc1 00038751 00000001 00000
[ 2614.407439] bea0: 00000018 00000000 e8000000 00000003 00000000 00000000 2831d
[ 2614.415573] bec0: 001067c4 ffffffc0 a82e8c0c 0000007f fffffffb ffffffff f3d31
[ 2614.423706] bee0: f3d38000 ffffffc1 00976000 ffffffc0 0098ec78 ffffffc0 00980
[ 2614.431841] bf00: f3d38000 ffffffc1 00975233 ffffffc0 0007d000 00000040 007d0
[ 2614.439976] bf20: 0061dd98 ffffffc0 f3d3bf60 ffffffc1 000855fc ffffffc0 f3d31
[ 2614.448111] [<ffffffc0000845a8>] el1_irq+0x68/0xc0                           
[ 2614.452877] [<ffffffc0000ed66c>] cpu_startup_entry+0x12c/0x1e4               
[ 2614.458679] [<ffffffc00008e8b8>] secondary_start_kernel+0xf8/0x108