Created attachment 848137 [details] First three oops messages (3.12.6-300.fc20.x86_64) Description of problem: Oops with IP in __slab_alloc Version-Release number of selected component (if applicable): 3.12.6-300.fc20.x86_64 How reproducible: Not sure how to reproduce. Will let you know if it happens again. Steps to Reproduce: 1. 2. 3. Actual results: BUG: unable to handle kernel paging request at 0000000040000020 IP: [<ffffffff816615eb>] __slab_alloc+0x116/0x4a2 PGD 7faceb067 PUD 0 Oops: 0000 [#1] SMP Modules linked in: rfcomm fuse xt_CHECKSUM tun ipt_MASQUERADE ip6t_REJECT xt_conntrack cfg80211 ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw bnep sch_fq vfat fat btrfs iTCO_wdt iTCO_vendor_support x86_pkg_temp_thermal coretemp snd_hda_codec_hdmi kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel snd_hda_codec_realtek raid6_pq libcrc32c microcode snd_usb_audio xor snd_usbmidi_lib snd_hda_intel snd_rawmidi snd_hda_codec serio_raw snd_hwdep i2c_i801 snd_seq btusb snd_seq_device bluetooth snd_pcm rfkill snd_page_alloc snd_timer mei_me r8169 snd lpc_ich mei mii mfd_core soundcore shpchp video binfmt_misc usb_storage radeon i2c_algo_bit drm_kms_helper ttm drm i2c_core [last unloaded: nf_conntrack_broadcast] CPU: 1 PID: 2971 Comm: pulseaudio Not tainted 3.12.6-300.fc20.x86_64 #1 Hardware name: Gigabyte Technology Co., Ltd. Z87-HD3/Z87-HD3, BIOS F6 08/03/2013 task: ffff8807fdffe930 ti: ffff8807fad10000 task.ti: ffff8807fad10000 RIP: 0010:[<ffffffff816615eb>] [<ffffffff816615eb>] __slab_alloc+0x116/0x4a2 RSP: 0018:ffff8807fad11ab8 EFLAGS: 00010006 RAX: 0000000040000000 RBX: ffff88083ec58ae0 RCX: 0000000000000000 RDX: 0000000000000296 RSI: 00000000000004d0 RDI: ffff88081acead00 RBP: ffff8807fad11b78 R08: ffff88083ec58ae0 R09: ffff88081acead00 R10: ffffffff8155691e R11: ffff8807fdffe930 R12: ffff88081acead00 R13: 0000000040000000 R14: 00000000ffffffff R15: 00000000ffffffff FS: 00007f3a57b8f7c0(0000) GS:ffff88083ec40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000040000020 CR3: 00000007f5a9b000 CR4: 00000000001407e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff811c2adb 0000000000000001 ffff88006227d40c ffff8807fad11af8 0000000000000000 0000000000000000 ffffffff00000000 0000000000000000 ffffffff8155691e 000004d000000002 0000000000000296 ffff8807fad11fd8 Call Trace: [<ffffffff811c2adb>] ? do_sys_poll+0x18b/0x560 [<ffffffff8155691e>] ? __alloc_skb+0x4e/0x2b0 [<ffffffff81196abc>] kmem_cache_alloc_node+0x9c/0x230 [<ffffffff8155691e>] __alloc_skb+0x4e/0x2b0 [<ffffffff81551b9a>] sock_alloc_send_pskb+0x1aa/0x3d0 [<ffffffff8160920e>] unix_stream_sendmsg+0x26e/0x400 [<ffffffff8154dceb>] sock_sendmsg+0x8b/0xc0 [<ffffffff811c7f6f>] ? touch_atime+0x10f/0x140 [<ffffffff8154de91>] SYSC_sendto+0x121/0x1c0 [<ffffffff811ae4c7>] ? vfs_read+0xf7/0x170 [<ffffffff8154e99e>] SyS_sendto+0xe/0x10 [<ffffffff81672129>] system_call_fastpath+0x16/0x1b Code: e8 12 83 64 24 48 03 83 e0 01 83 64 24 38 01 48 69 c0 20 91 00 00 48 89 44 24 20 48 8b 43 18 48 85 c0 74 20 49 89 c5 48 89 43 10 <48> 8b 40 20 44 8b 7c 24 34 48 c7 03 00 00 00 00 48 89 43 18 e9 RIP [<ffffffff816615eb>] __slab_alloc+0x116/0x4a2 RSP <ffff8807fad11ab8> CR2: 0000000040000020 ---[ end trace 7b09d9feedb2e65b ]--- BUG: unable to handle kernel paging request at 0000000040000000 IP: [<ffffffff81660c65>] slab_out_of_memory+0x118/0x118 PGD 0 Oops: 0000 [#2] SMP Modules linked in: rfcomm fuse xt_CHECKSUM tun ipt_MASQUERADE ip6t_REJECT xt_conntrack cfg80211 ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw bnep sch_fq vfat fat btrfs iTCO_wdt iTCO_vendor_support x86_pkg_temp_thermal coretemp snd_hda_codec_hdmi kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel snd_hda_codec_realtek raid6_pq libcrc32c microcode snd_usb_audio xor snd_usbmidi_lib snd_hda_intel snd_rawmidi snd_hda_codec serio_raw snd_hwdep i2c_i801 snd_seq btusb snd_seq_device bluetooth snd_pcm rfkill snd_page_alloc snd_timer mei_me r8169 snd lpc_ich mei mii mfd_core soundcore shpchp video binfmt_misc usb_storage radeon i2c_algo_bit drm_kms_helper ttm drm i2c_core [last unloaded: nf_conntrack_broadcast] CPU: 1 PID: 2860 Comm: dbus-daemon Tainted: G D 3.12.6-300.fc20.x86_64 #1 Hardware name: Gigabyte Technology Co., Ltd. Z87-HD3/Z87-HD3, BIOS F6 08/03/2013 task: ffff88080103f2c0 ti: ffff8807e540c000 task.ti: ffff8807e540c000 RIP: 0010:[<ffffffff81660c65>] [<ffffffff81660c65>] slab_out_of_memory+0x118/0x118 RSP: 0018:ffff8807e540d9c0 EFLAGS: 00010046 RAX: 0000000000000292 RBX: ffff88083ec58ae0 RCX: ffffffff8155691e RDX: 0000000000000292 RSI: 00000000000004d0 RDI: 0000000040000000 RBP: ffff8807e540da88 R08: ffff88083ec58ae0 R09: ffff88081acead00 R10: ffffffff8155691e R11: ffff88080103f2c0 R12: ffff88081acead00 R13: 0000000040000000 R14: 00000000ffffffff R15: 00000000ffffffff FS: 00007f991198f840(0000) GS:ffff88083ec40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000040000000 CR3: 00000007fdc69000 CR4: 00000000001407e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff816618e3 ffff8807e540da98 0000000000000296 ffff880811a78000 0000000000000007 ffff880811162f20 0000000000000351 0000000000000000 ffff8807e563ba08 ffffffff8155691e 000004d000000000 0000000000000292 Call Trace: [<ffffffff816618e3>] ? __slab_alloc+0x40e/0x4a2 [<ffffffff8155691e>] ? __alloc_skb+0x4e/0x2b0 [<ffffffff81196abc>] kmem_cache_alloc_node+0x9c/0x230 [<ffffffff8155691e>] __alloc_skb+0x4e/0x2b0 [<ffffffff81551b9a>] sock_alloc_send_pskb+0x1aa/0x3d0 [<ffffffff81088138>] ? __kernel_text_address+0x58/0x80 [<ffffffff8160920e>] unix_stream_sendmsg+0x26e/0x400 [<ffffffff8154dceb>] sock_sendmsg+0x8b/0xc0 [<ffffffff811917f1>] ? set_track+0x61/0x1b0 [<ffffffff81660f81>] ? free_debug_processing+0x1de/0x222 [<ffffffff811424aa>] ? unlock_page+0x2a/0x30 [<ffffffff8116a0bc>] ? do_wp_page+0x3ac/0x810 [<ffffffff8154e559>] ___sys_sendmsg+0x3a9/0x3c0 [<ffffffff8166d80c>] ? __do_page_fault+0x20c/0x540 [<ffffffff811cc58e>] ? mntput_no_expire+0x3e/0x120 [<ffffffff811cc694>] ? mntput+0x24/0x40 [<ffffffff811b000c>] ? __fput+0x16c/0x230 [<ffffffff8154ec62>] __sys_sendmsg+0x42/0x80 [<ffffffff8154ecb2>] SyS_sendmsg+0x12/0x20 [<ffffffff81672129>] system_call_fastpath+0x16/0x1b Code: c3 be 00 02 00 00 48 c7 c7 40 b5 cf 81 48 63 d3 e8 31 42 cb ff 3d 00 02 00 00 89 c3 41 0f 4f de eb 99 5b 41 5c 41 5d 41 5e 5d c3 <48> 8b 07 a8 80 75 02 0f 0b 48 8b 17 b0 01 80 e2 40 74 0c 55 89 RIP [<ffffffff81660c65>] slab_out_of_memory+0x118/0x118 RSP <ffff8807e540d9c0> CR2: 0000000040000000 ---[ end trace 7b09d9feedb2e65c ]--- BUG: unable to handle kernel paging request at 0000000040000000 IP: [<ffffffff81660c65>] slab_out_of_memory+0x118/0x118 PGD 7faf37067 PUD 0 Oops: 0000 [#3] SMP Modules linked in: rfcomm fuse xt_CHECKSUM tun ipt_MASQUERADE ip6t_REJECT xt_conntrack cfg80211 ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw bnep sch_fq vfat fat btrfs iTCO_wdt iTCO_vendor_support x86_pkg_temp_thermal coretemp snd_hda_codec_hdmi kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel snd_hda_codec_realtek raid6_pq libcrc32c microcode snd_usb_audio xor snd_usbmidi_lib snd_hda_intel snd_rawmidi snd_hda_codec serio_raw snd_hwdep i2c_i801 snd_seq btusb snd_seq_device bluetooth snd_pcm rfkill snd_page_alloc snd_timer mei_me r8169 snd lpc_ich mei mii mfd_core soundcore shpchp video binfmt_misc usb_storage radeon i2c_algo_bit drm_kms_helper ttm drm i2c_core [last unloaded: nf_conntrack_broadcast] CPU: 1 PID: 788 Comm: Xorg Tainted: G D 3.12.6-300.fc20.x86_64 #1 Hardware name: Gigabyte Technology Co., Ltd. Z87-HD3/Z87-HD3, BIOS F6 08/03/2013 task: ffff8807fa3fd610 ti: ffff8807fac56000 task.ti: ffff8807fac56000 RIP: 0010:[<ffffffff81660c65>] [<ffffffff81660c65>] slab_out_of_memory+0x118/0x118 RSP: 0018:ffff8807fac57a70 EFLAGS: 00010046 RAX: 0000000000000296 RBX: ffff88083ec58ae0 RCX: ffffffff8155691e RDX: 0000000000000296 RSI: 00000000000004d0 RDI: 0000000040000000 RBP: ffff8807fac57b40 R08: ffff88083ec58ae0 R09: ffff88081acead00 R10: ffffffff8155691e R11: ffff8807fa3fd610 R12: ffff88081acead00 R13: 0000000040000000 R14: 00000000ffffffff R15: 00000000ffffffff FS: 00007f05352929c0(0000) GS:ffff88083ec40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000040000000 CR3: 00000007fde69000 CR4: 00000000001407e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff816618e3 ffff88083ec43fc0 ffff8807fac57ad0 ffff8807fac57b00 ffffffff8101484f ffff8807fac57acc 0000000081556e7e ffff88083ec43fc0 0000000000000001 ffffffff8155691e 000004d0fac57b28 0000000000000296 Call Trace: [<ffffffff816618e3>] ? __slab_alloc+0x40e/0x4a2 [<ffffffff8101484f>] ? dump_trace+0x16f/0x2b0 [<ffffffff8155691e>] ? __alloc_skb+0x4e/0x2b0 [<ffffffff815546a7>] ? kfree_skbmem+0x37/0x90 [<ffffffff810207eb>] ? save_stack_trace+0x2b/0x50 [<ffffffff81196abc>] kmem_cache_alloc_node+0x9c/0x230 [<ffffffff8155691e>] __alloc_skb+0x4e/0x2b0 [<ffffffff81551b9a>] sock_alloc_send_pskb+0x1aa/0x3d0 [<ffffffff8160920e>] unix_stream_sendmsg+0x26e/0x400 [<ffffffff8154cbfe>] sock_aio_write+0xfe/0x130 [<ffffffff811adf8c>] do_sync_readv_writev+0x4c/0x80 [<ffffffff811af3cb>] do_readv_writev+0xbb/0x230 [<ffffffff811af5d5>] vfs_writev+0x35/0x60 [<ffffffff811af709>] SyS_writev+0x49/0xc0 [<ffffffff810f12e6>] ? __audit_syscall_exit+0x1f6/0x2a0 [<ffffffff81672129>] system_call_fastpath+0x16/0x1b Code: c3 be 00 02 00 00 48 c7 c7 40 b5 cf 81 48 63 d3 e8 31 42 cb ff 3d 00 02 00 00 89 c3 41 0f 4f de eb 99 5b 41 5c 41 5d 41 5e 5d c3 <48> 8b 07 a8 80 75 02 0f 0b 48 8b 17 b0 01 80 e2 40 74 0c 55 89 RIP [<ffffffff81660c65>] slab_out_of_memory+0x118/0x118 RSP <ffff8807fac57a70> CR2: 0000000040000000 ---[ end trace 7b09d9feedb2e65d ]--- Expected results: Oops- and panic-free linux Additional info: I've had some other crashes & hangs in the last month, so I've got slub_debug=FZPU on the kernel cmdline. Oh, and cgroup_disable=memory. No other exotic options. On this occasion, the system staggered on with a frozen display for a few more minutes (presumably without any new slabs). I tried various alt-sysrq keys to try to get something into the system log, before the system crashed, triggering kdump and reboot. The dmesg from the resulting vmcore is full of alt-sysrq output. Let me know if the first oops captured above is uninterpretable and you want me to download the appropriate vmlinux and try to get more info from the vmcore file.
0000000040000020 That 4 could be a random bit-flip. Give memtest86 a try for a while.
Thanks for the tip. I've previously been suspicious, and had already run memtest86 for ~12 hours. Rate of mysterious crashes has dropped significantly since https://bugzilla.kernel.org/show_bug.cgi?id=68171 and my physical removal of that USB wifi dongle, which I had thought to be the sole cause (until this oops in __slab_alloc). Since your suggestion, I've run memtest86 again for 20 hours, multiple passes. Half way through I swapped each pair of DIMMs in their slots to try to improve coverage. Have run memtester on 30G out of 32G RAM for another 16 hours, multiple passes. So far no errors detected from either program. In case you were wondering, this machine is not overclocked and DRAM timing has not been modified from the default. Any other advice or suggestions? Extra debug options I should include on the command line? cmdline: BOOT_IMAGE=/vmlinuz-3.12.6-300.fc20.x86_64 root=/dev/disk/by-id/ata-INTEL_SSDSC2BW120A4_CVDA3360011H1207GN-part1 ro vconsole.font=latarcyrheb-sun16 vconsole.keymap=us drm.vblankoffdelay=1 LANG=en_AU.UTF-8 cgroup_disable=memory crashkernel=128M slub_debug=FZPU radeon.dpm=0 rhgb I'll do my best to capture and forward any further crashes; so far there haven't been any, but I've mostly been testing memory rather than using the machine productively. (ABRT 2.1.11-1.fc20 seems to do nothing with my kdump/vmcore files, requiring manual processing, but I don't currently have the inclination to strace it and report that bug in a useful way.)
I've been running 3.12.7-300.fc20.x86_64+debug, following suggestions in another bug report that originally looked like a wireless driver problem (https://bugzilla.kernel.org/show_bug.cgi?id=68171). Today, after >34 hours uptime, another bug message: ============================================================================= BUG vm_area_struct (Not tainted): Poison overwritten ----------------------------------------------------------------------------- INFO: 0xffff8802ca728039-0xffff8802ca728039. First byte 0x4b instead of 0x6b INFO: Allocated in dup_mm+0x230/0x710 age=112633 cpu=0 pid=369 __slab_alloc+0x3eb/0x4fe kmem_cache_alloc+0x294/0x340 dup_mm+0x230/0x710 copy_process.part.23+0x12d4/0x1890 do_fork+0xce/0x450 SyS_clone+0x16/0x20 stub_clone+0x69/0x90 INFO: Freed in remove_vma+0x76/0x80 age=109627 cpu=5 pid=28464 __slab_free+0x3a/0x382 kmem_cache_free+0x356/0x370 remove_vma+0x76/0x80 exit_mmap+0xf4/0x170 mmput+0x7f/0x110 do_exit+0x2a5/0xcd0 do_group_exit+0x4c/0xc0 SyS_exit_group+0x14/0x20 system_call_fastpath+0x16/0x1b INFO: Slab 0xffffea000b29ca00 objects=32 used=32 fp=0x (null) flags=0x5ff00000004080 INFO: Object 0xffff8802ca728000 @offset=0 fp=0xffff8802ca72aa00 Object ffff8802ca728000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728020: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728030: 6b 6b 6b 6b 6b 6b 6b 6b 6b 4b 6b 6b 6b 6b 6b 6b kkkkkkkkkKkkkkkk Object ffff8802ca728040: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728050: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728060: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728070: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728080: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca728090: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca7280a0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff8802ca7280b0: 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkk. Redzone ffff8802ca7280b8: bb bb bb bb bb bb bb bb ........ Padding ffff8802ca7281f8: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ CPU: 7 PID: 5195 Comm: Xorg Tainted: G B 3.12.7-300.fc20.x86_64+debug #1 Hardware name: Gigabyte Technology Co., Ltd. Z87-HD3/Z87-HD3, BIOS F6 08/03/2013 ffff8802ca728000 ffff8807ec29bbd8 ffffffff81749d2b ffff88081d019200 ffff8807ec29bc18 ffffffff811d40fd 0000000000000008 ffff880200000001 ffff8802ca72803a ffff88081d019200 000000000000006b ffff8802ca728000 Call Trace: [<ffffffff81749d2b>] dump_stack+0x54/0x74 [<ffffffff811d40fd>] print_trailer+0x14d/0x200 [<ffffffff811d42ef>] check_bytes_and_report+0xcf/0x110 [<ffffffff811d5177>] check_object+0x1d7/0x250 [<ffffffff811b28e8>] ? mmap_region+0x348/0x5d0 [<ffffffff817474b2>] alloc_debug_processing+0x76/0x118 [<ffffffff817480ed>] __slab_alloc+0x3eb/0x4fe [<ffffffffa00171e9>] ? drm_gem_object_lookup+0x29/0x160 [drm] [<ffffffff811b28e8>] ? mmap_region+0x348/0x5d0 [<ffffffff811d6cc4>] kmem_cache_alloc+0x294/0x340 [<ffffffff811b28e8>] ? mmap_region+0x348/0x5d0 [<ffffffff811b28e8>] mmap_region+0x348/0x5d0 [<ffffffff811b2ed0>] do_mmap_pgoff+0x360/0x3f0 [<ffffffff8119cf50>] vm_mmap_pgoff+0x90/0xc0 [<ffffffff811b1423>] SyS_mmap_pgoff+0x1d3/0x270 [<ffffffff8101e7e2>] SyS_mmap+0x22/0x30 [<ffffffff8175d029>] system_call_fastpath+0x16/0x1b FIX vm_area_struct: Restoring 0xffff8802ca728039-0xffff8802ca728039=0x6b FIX vm_area_struct: Marking all objects used --- And after slabinfo --validate: SLUB: vm_area_struct 1086 slabs counted but counter=1087 Is that change from 0x6b to 0x4b another bitflip? If so, why can't I trigger it with memory testing programs, only by exercising the kernel? I've run multiple loops of memtest86 and also memtester, at least 72 hours in total, with no errors detected. Other kernel messages that made me nervous: cryptomgr_test (60) used greatest stack depth: 6360 bytes left cryptomgr_test (61) used greatest stack depth: 6232 bytes left modprobe (68) used greatest stack depth: 5576 bytes left cryptomgr_test (65) used greatest stack depth: 5208 bytes left ata_id (209) used greatest stack depth: 5000 bytes left mount (256) used greatest stack depth: 4232 bytes left systemd-udevd (187) used greatest stack depth: 3224 bytes left typefind:sink (3719) used greatest stack depth: 3112 bytes left stress (14329) used greatest stack depth: 2792 bytes left kworker/u16:4 (108) used greatest stack depth: 1928 bytes left btrfs (2954) used greatest stack depth: 1856 bytes left 1856 bytes left means that the other 78% of the stack was consumed. I guess the debug options in this kernel make stack usage a bit heavier than a general purpose kernel, but could stack overflows explain the scribbling on kernel memory?
it does look like another single bitflip. Very puzzling, as it does seem like a hardware fault of some kind, which memtest would normally pick up. The stack messages are just informational, nothing to worry about. No further ideas right now I'm afraid.
*********** MASS BUG UPDATE ************** We apologize for the inconvenience. There is a large number of bugs to go through and several of them have gone stale. Due to this, we are doing a mass bug update across all of the Fedora 20 kernel bugs. Fedora 20 has now been rebased to 3.13.4-200.fc20. Please test this kernel update and let us know if you issue has been resolved or if it is still present with the newer kernel. If you experience different issues, please open a new bug report for those.
*********** MASS BUG UPDATE ************** This bug has been in a needinfo state for several weeks and is being closed with insufficient data due to inactivity. If this is still an issue with Fedora 20, please feel free to reopen the bug and provide the additional information requested.