postgresql core dump issue

Hi,

I've been experiencing unusual core dumps that says postgres Not tainted
and I don't know where to start. I guess this is a kernel issue and
tried 3.13.0-49 and 3.13.0-53 but I got no good results. This is happening
on 2 of our Ubuntu 14.04.2 servers with
postgresql-9.3 9.3.5-0ubuntu0.14.04.1. i am also using the same postgresql
version and kernel to other 10 14.04.2 and doesn't encounter this error.
Below is the dump:

kernel: [651454.831139] ------------[ cut here ]------------
kernel: [651454.831155] WARNING: CPU: 1 PID: 20500 at
/build/buildd/linux-3.13.0/net/core/dst.c:285 dst_release+0x45/0x60()
kernel: [651454.831158] Modules linked in: btrfs raid6_pq xor ufs qnx4
hfsplus hfs minix ntfs msdos jfs xfs i2c_piix4 serio_raw mac_hid drbd
lru_cache libcrc32c lp parport pata_acpi
kernel: [651454.831179] CPU: 1 PID: 20500 Comm: postgres Not tainted
3.13.0-53-generic #89-Ubuntu
kernel: [651454.831181] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
kernel: [651454.831183] 0000000000000009 ffff88002e785b18 ffffffff81722e1e
0000000000000000
kernel: [651454.831186] ffff88002e785b50 ffffffff810677fd ffff88003aa78000
00000000ffffffff
kernel: [651454.831189] ffff88003abb8440 0000000000000000 0000000000000000
ffff88002e785b60
kernel: [651454.831192] Call Trace:
kernel: [651454.831200] [<ffffffff81722e1e>] dump_stack+0x45/0x56
kernel: [651454.831205] [<ffffffff810677fd>] warn_slowpath_common+0x7d/0xa0
kernel: [651454.831208] [<ffffffff810678da>] warn_slowpath_null+0x1a/0x20
kernel: [651454.831211] [<ffffffff8162f4e5>] dst_release+0x45/0x60
kernel: [651454.831258] [<ffffffff816102e9>] sk_dst_check+0xb9/0xe0
kernel: [651454.831264] [<ffffffff816c2f1f>]
ip6_sk_dst_lookup_flow+0x2f/0x1b0
kernel: [651454.831268] [<ffffffff81612af8>] ? release_sock+0x118/0x170
kernel: [651454.831272] [<ffffffff816dde8e>] udpv6_sendmsg+0x61e/0xb10
kernel: [651454.831277] [<ffffffff8166d322>] ? tcp_recvmsg+0x6c2/0xb80
kernel: [651454.831283] [<ffffffff81695364>] inet_sendmsg+0x64/0xb0
kernel: [651454.831303] [<ffffffff81314527>] ?
apparmor_socket_sendmsg+0x17/0x20
kernel: [651454.831307] [<ffffffff8160de3b>] sock_sendmsg+0x8b/0xc0
kernel: [651454.831314] [<ffffffff8172eef4>] ? __do_page_fault+0x204/0x570
kernel: [651454.831317] [<ffffffff8160e381>] SYSC_sendto+0x121/0x1c0
kernel: [651454.831322] [<ffffffff8104f2bf>] ?
kvm_clock_get_cycles+0x1f/0x30
kernel: [651454.831327] [<ffffffff810cd9da>] ? __getnstimeofday+0x3a/0xc0
kernel: [651454.831330] [<ffffffff810cda6e>] ? getnstimeofday+0xe/0x30
kernel: [651454.831333] [<ffffffff810cdaaa>] ? do_gettimeofday+0x1a/0x50
kernel: [651454.831336] [<ffffffff8160ed6e>] SyS_sendto+0xe/0x10
kernel: [651454.831339] [<ffffffff8173391d>] system_call_fastpath+0x1a/0x1f
kernel: [651454.831341] ---[ end trace 5e06bdd4ad2125b1 ]---
kernel: [653314.515991] ------------[ cut here ]------------
kernel: [653314.516010] WARNING: CPU: 1 PID: 32055 at
/build/buildd/linux-3.13.0/net/core/dst.c:285 dst_release+0x45/0x60()
kernel: [653314.516056] Modules linked in: btrfs raid6_pq xor ufs qnx4
hfsplus hfs minix ntfs msdos jfs xfs i2c_piix4 serio_raw mac_hid drbd
lru_cache libcrc32c lp parport pata_acpi
kernel: [653314.516073] CPU: 1 PID: 32055 Comm: postgres Tainted: G
W 3.13.0-53-generic #89-Ubuntu
kernel: [653314.516075] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
kernel: [653314.516076] 0000000000000009 ffff88003a445b58 ffffffff81722e1e
0000000000000000
kernel: [653314.516079] ffff88003a445b90 ffffffff810677fd ffff88003aa78000
00000000ffffffff
kernel: [653314.516081] ffff88003abb87b8 00000000000003d0 ffff88003aa78000
ffff88003a445ba0
kernel: [653314.516083] Call Trace:
kernel: [653314.516090] [<ffffffff81722e1e>] dump_stack+0x45/0x56
kernel: [653314.516095] [<ffffffff810677fd>] warn_slowpath_common+0x7d/0xa0
kernel: [653314.516097] [<ffffffff810678da>] warn_slowpath_null+0x1a/0x20
kernel: [653314.516099] [<ffffffff8162f4e5>] dst_release+0x45/0x60
kernel: [653314.516103] [<ffffffff8161033c>] sk_setup_caps+0x2c/0xd0
kernel: [653314.516107] [<ffffffff816ddb8c>] udpv6_sendmsg+0x31c/0xb10
kernel: [653314.516111] [<ffffffff8166d322>] ? tcp_recvmsg+0x6c2/0xb80
kernel: [653314.516116] [<ffffffff81695364>] inet_sendmsg+0x64/0xb0
kernel: [653314.516123] [<ffffffff81314527>] ?
apparmor_socket_sendmsg+0x17/0x20
kernel: [653314.516125] [<ffffffff8160de3b>] sock_sendmsg+0x8b/0xc0
kernel: [653314.516130] [<ffffffff81157b50>] ? free_pages.part.64+0x40/0x50
kernel: [653314.516133] [<ffffffff81157b73>] ? free_pages+0x13/0x20
kernel: [653314.516137] [<ffffffff81176635>] ? tlb_finish_mmu+0x35/0x60
kernel: [653314.516139] [<ffffffff8160e381>] SYSC_sendto+0x121/0x1c0
kernel: [653314.516144] [<ffffffff8104f2bf>] ?
kvm_clock_get_cycles+0x1f/0x30
kernel: [653314.516148] [<ffffffff810cd9da>] ? __getnstimeofday+0x3a/0xc0
kernel: [653314.516150] [<ffffffff810cda6e>] ? getnstimeofday+0xe/0x30
kernel: [653314.516152] [<ffffffff810cdaaa>] ? do_gettimeofday+0x1a/0x50
kernel: [653314.516155] [<ffffffff8160ed6e>] SyS_sendto+0xe/0x10
kernel: [653314.516158] [<ffffffff8173391d>] system_call_fastpath+0x1a/0x1f
kernel: [653314.516160] ---[ end trace 5e06bdd4ad2125b2 ]---

Thanks,
Norbert