f4b3ec4e6a
Naresh Kamboju noted the following oops during execution of selftest tools/testing/selftests/bpf/test_tunnel.sh on x86_64: [ 274.120445] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 274.128285] #PF error: [INSTR] [ 274.131351] PGD 8000000414a0e067 P4D 8000000414a0e067 PUD 3b6334067 PMD 0 [ 274.138241] Oops: 0010 [#1] SMP PTI [ 274.141734] CPU: 1 PID: 11464 Comm: ping Not tainted 5.0.0-rc4-next-20190129 #1 [ 274.149046] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.0b 07/27/2017 [ 274.156526] RIP: 0010: (null) [ 274.160280] Code: Bad RIP value. [ 274.163509] RSP: 0018:ffffbc9681f83540 EFLAGS: 00010286 [ 274.168726] RAX: 0000000000000000 RBX: ffffdc967fa80a18 RCX: 0000000000000000 [ 274.175851] RDX: ffff9db2ee08b540 RSI: 000000000000000e RDI: ffffdc967fa809a0 [ 274.182974] RBP: ffffbc9681f83580 R08: ffff9db2c4d62690 R09: 000000000000000c [ 274.190098] R10: 0000000000000000 R11: ffff9db2ee08b540 R12: ffff9db31ce7c000 [ 274.197222] R13: 0000000000000001 R14: 000000000000000c R15: ffff9db3179cf400 [ 274.204346] FS: 00007ff4ae7c5740(0000) GS:ffff9db31fa80000(0000) knlGS:0000000000000000 [ 274.212424] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 274.218162] CR2: ffffffffffffffd6 CR3: 00000004574da004 CR4: 00000000003606e0 [ 274.225292] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 274.232416] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 274.239541] Call Trace: [ 274.241988] ? tnl_update_pmtu+0x296/0x3b0 [ 274.246085] ip_md_tunnel_xmit+0x1bc/0x520 [ 274.250176] gre_fb_xmit+0x330/0x390 [ 274.253754] gre_tap_xmit+0x128/0x180 [ 274.257414] dev_hard_start_xmit+0xb7/0x300 [ 274.261598] sch_direct_xmit+0xf6/0x290 [ 274.265430] __qdisc_run+0x15d/0x5e0 [ 274.269007] __dev_queue_xmit+0x2c5/0xc00 [ 274.273011] ? dev_queue_xmit+0x10/0x20 [ 274.276842] ? eth_header+0x2b/0xc0 [ 274.280326] dev_queue_xmit+0x10/0x20 [ 274.283984] ? dev_queue_xmit+0x10/0x20 [ 274.287813] arp_xmit+0x1a/0xf0 [ 274.290952] arp_send_dst.part.19+0x46/0x60 [ 274.295138] arp_solicit+0x177/0x6b0 [ 274.298708] ? mod_timer+0x18e/0x440 [ 274.302281] neigh_probe+0x57/0x70 [ 274.305684] __neigh_event_send+0x197/0x2d0 [ 274.309862] neigh_resolve_output+0x18c/0x210 [ 274.314212] ip_finish_output2+0x257/0x690 [ 274.318304] ip_finish_output+0x219/0x340 [ 274.322314] ? ip_finish_output+0x219/0x340 [ 274.326493] ip_output+0x76/0x240 [ 274.329805] ? ip_fragment.constprop.53+0x80/0x80 [ 274.334510] ip_local_out+0x3f/0x70 [ 274.337992] ip_send_skb+0x19/0x40 [ 274.341391] ip_push_pending_frames+0x33/0x40 [ 274.345740] raw_sendmsg+0xc15/0x11d0 [ 274.349403] ? __might_fault+0x85/0x90 [ 274.353151] ? _copy_from_user+0x6b/0xa0 [ 274.357070] ? rw_copy_check_uvector+0x54/0x130 [ 274.361604] inet_sendmsg+0x42/0x1c0 [ 274.365179] ? inet_sendmsg+0x42/0x1c0 [ 274.368937] sock_sendmsg+0x3e/0x50 [ 274.372460] ___sys_sendmsg+0x26f/0x2d0 [ 274.376293] ? lock_acquire+0x95/0x190 [ 274.380043] ? __handle_mm_fault+0x7ce/0xb70 [ 274.384307] ? lock_acquire+0x95/0x190 [ 274.388053] ? __audit_syscall_entry+0xdd/0x130 [ 274.392586] ? ktime_get_coarse_real_ts64+0x64/0xc0 [ 274.397461] ? __audit_syscall_entry+0xdd/0x130 [ 274.401989] ? trace_hardirqs_on+0x4c/0x100 [ 274.406173] __sys_sendmsg+0x63/0xa0 [ 274.409744] ? __sys_sendmsg+0x63/0xa0 [ 274.413488] __x64_sys_sendmsg+0x1f/0x30 [ 274.417405] do_syscall_64+0x55/0x190 [ 274.421064] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 274.426113] RIP: 0033:0x7ff4ae0e6e87 [ 274.429686] Code: 64 89 02 48 c7 c0 ff ff ff ff eb b9 0f 1f 80 00 00 00 00 8b 05 ca d9 2b 00 48 63 d2 48 63 ff 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 53 48 89 f3 48 83 ec 10 48 89 7c 24 08 [ 274.448422] RSP: 002b:00007ffcd9b76db8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 274.455978] RAX: ffffffffffffffda RBX: 0000000000000040 RCX: 00007ff4ae0e6e87 [ 274.463104] RDX: 0000000000000000 RSI: 00000000006092e0 RDI: 0000000000000003 [ 274.470228] RBP: 0000000000000000 R08: 00007ffcd9bc40a0 R09: 00007ffcd9bc4080 [ 274.477349] R10: 000000000000060a R11: 0000000000000246 R12: 0000000000000003 [ 274.484475] R13: 0000000000000016 R14: 00007ffcd9b77fa0 R15: 00007ffcd9b78da4 [ 274.491602] Modules linked in: cls_bpf sch_ingress iptable_filter ip_tables algif_hash af_alg x86_pkg_temp_thermal fuse [last unloaded: test_bpf] [ 274.504634] CR2: 0000000000000000 [ 274.507976] ---[ end trace 196d18386545eae1 ]--- [ 274.512588] RIP: 0010: (null) [ 274.516334] Code: Bad RIP value. [ 274.519557] RSP: 0018:ffffbc9681f83540 EFLAGS: 00010286 [ 274.524775] RAX: 0000000000000000 RBX: ffffdc967fa80a18 RCX: 0000000000000000 [ 274.531921] RDX: ffff9db2ee08b540 RSI: 000000000000000e RDI: ffffdc967fa809a0 [ 274.539082] RBP: ffffbc9681f83580 R08: ffff9db2c4d62690 R09: 000000000000000c [ 274.546205] R10: 0000000000000000 R11: ffff9db2ee08b540 R12: ffff9db31ce7c000 [ 274.553329] R13: 0000000000000001 R14: 000000000000000c R15: ffff9db3179cf400 [ 274.560456] FS: 00007ff4ae7c5740(0000) GS:ffff9db31fa80000(0000) knlGS:0000000000000000 [ 274.568541] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 274.574277] CR2: ffffffffffffffd6 CR3: 00000004574da004 CR4: 00000000003606e0 [ 274.581403] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 274.588535] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 274.595658] Kernel panic - not syncing: Fatal exception in interrupt [ 274.602046] Kernel Offset: 0x14400000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 274.612827] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]--- [ 274.620387] ------------[ cut here ]------------ I'm also seeing the same failure on x86_64, and it reproduces consistently. >From poking around it looks like the skb's dst entry is being used to calculate the mtu in: mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu; ...but because that dst_entry has an "ops" value set to md_dst_ops, the various ops (including mtu) are not set: crash> struct sk_buff._skb_refdst ffff928f87447700 -x _skb_refdst = 0xffffcd6fbf5ea590 crash> struct dst_entry.ops 0xffffcd6fbf5ea590 ops = 0xffffffffa0193800 crash> struct dst_ops.mtu 0xffffffffa0193800 mtu = 0x0 crash> I confirmed that the dst entry also has dst->input set to dst_md_discard, so it looks like it's an entry that's been initialized via __metadata_dst_init alright. I think the fix here is to use skb_valid_dst(skb) - it checks for DST_METADATA also, and with that fix in place, the problem - which was previously 100% reproducible - disappears. The below patch resolves the panic and all bpf tunnel tests pass without incident. Fixes: c8b34e680a09 ("ip_tunnel: Add tnl_update_pmtu in ip_md_tunnel_xmit") Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Tested-by: Anders Roxell <anders.roxell@linaro.org> Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Tested-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
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