I've got a CentOS 7 kernel that has been slightly modified, but the mm subsystem hasn't been touched. I'm hoping you can give me some guidance. I have an intermittent Oops that looks like what is below. The issue is currently occurring on one CPU of one system, but has been seen before infrequently. Once the corruption occurs it causes an Oops on every call to __mpol_dup() on this CPU. Basically it appears that __mpol_dup() is failing because the value of c->freelist in slab_alloc_node() is corrupt, causing the call to get_freepointer_safe(s, object) to Oops because it tries to dereference "object + s->offset". (Where s->offset is zero.) In the trace, "kmem_cache_alloc+0x87" maps to the following assembly: 0xffffffff8118be17 <+135>: mov (%r12,%rax,1),%rbx This corresponds to this line in get_freepointer(): return *(void **)(object + s->offset); In the assembly code, R12 is "object", and RAX is s->offset. So the question becomes, why is "object" (which corresponds to c->freelist) corrupt? Looking at the value of R12 (0x1ada8000), it's nonzero but also not a valid pointer. Does the value mean anything to you? (I'm not really a memory subsystem guy, so I'm hoping you might have some ideas.) Do you have any suggestions on how to track down what's going on here? Thanks, Chris PS: Please CC me on replies, I'm not subscribed to the list. 2016-09-24T16:43:45.125 controller-1 kernel: alert [90390.702162] BUG: unable to handle kernel paging request at 000000001ada8000 2016-09-24T16:43:45.125 controller-1 kernel: alert [90390.709965] IP: [<ffffffff8118be17>] kmem_cache_alloc+0x87/0x250 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.716689] PGD 0 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.718945] Oops: 0000 [#43] PREEMPT SMP 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.723454] Modules linked in: target_core_pscsi target_core_file target_core_iblock iscsi_target_mod target_core_mod dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio iptable_raw xt_CHECKSUM xt_connmark iptable_ mangle nbd ebtable_filter ebtables igb_uio(OE) uio drbd(OE) libcrc32c nf_log_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables virtio_net nf_log_ipv4 nf_log_common xt_LOG xt_limit xt_conntrack iptable_filter xt_nat xt_comment xt_multiport iptable_nat nf_conn track_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack veth nfsv3 nfs fscache 8021q garp stp mrp llc cls_u32 sch_sfq sch_htb dm_mod iTCO_wdt iTCO_vendor_support ipmi_devintf intel_powerclamp coretemp kvm_intel kvm crc32_pclmul ghash_clmulni_intel aesni_intel glue_helper lrw gf128mul ablk_helper cryptd lpc_ich mfd_core mei_me mei i2c_i801 ipmi_si ipmi_msghandler acpi_power_meter wrs_avp(OE) nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables ext4 jbd2 sd_mod crc_t10dif crct10dif_generic crct10dif_pclmul crct10dif_common crc32c_intel ahc i libahci ixgbe mdio igb i2c_algo_bit i2c_core libata dca i40e(OE) vxlan ip6_udp_tunnel udp_tunnel ptp pps_core 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.836474] CPU: 48 PID: 42192 Comm: qemu-kvm Tainted: G D OE ------------ 3.10.0-327.28.3.6.tis.x86_64 #1 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.848328] Hardware name: Intel Corporation S2600WT2R/S2600WT2R, BIOS SE5C610.86B.01.01.0016.033120161139 03/31/2016 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.860181] task: ffff880463f75a90 ti: ffff8804120f0000 task.ti: ffff8804120f0000 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.868540] RIP: 0010:[<ffffffff8118be17>] [<ffffffff8118be17>] kmem_cache_alloc+0x87/0x250 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.877980] RSP: 0018:ffff8804120f3d40 EFLAGS: 00010286 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.883913] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000019230 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.891883] RDX: 0000000000019130 RSI: 00000000000000d0 RDI: ffff8804120f3fd8 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.899853] RBP: ffff8804120f3d88 R08: 0000000000018710 R09: ffffffff811832e8 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.907823] R10: 0000000000000000 R11: ffffffffffffff83 R12: 000000001ada8000 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.915794] R13: 00000000000000d0 R14: ffff88103ec06200 R15: ffff88103ec06200 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.923765] FS: 00007fb6cb236e00(0000) GS:ffff88103f540000(0000) knlGS:0000000000000000 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.932804] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.939222] CR2: 000000001ada8000 CR3: 0000000464152000 CR4: 00000000003427e0 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.947194] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.955166] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.963135] Stack: 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.965380] 00ff880400000002 0000000000000246 ffff88107ffda000 00000000997694b3 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.973688] 0000000000000000 ffff88046d4815a8 00000000003d0f00 ffff8802c8003c60 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.981996] ffff880463f75a90 ffff8804120f3e38 ffffffff811832e8 ffff88107ffda000 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.990304] Call Trace: 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.993039] [<ffffffff811832e8>] __mpol_dup+0x38/0x140 2016-09-24T16:43:45.125 controller-1 kernel: warning [90390.998876] [<ffffffff8118bea2>] ? kmem_cache_alloc+0x112/0x250 2016-09-24T16:43:45.125 controller-1 kernel: warning [90391.005591] [<ffffffff8100be69>] ? read_tsc+0x9/0x10 2016-09-24T16:43:45.125 controller-1 kernel: warning [90391.011235] [<ffffffff8105ef91>] copy_process.part.30+0x611/0x1570 2016-09-24T16:43:45.125 controller-1 kernel: warning [90391.018230] [<ffffffff810600d1>] do_fork+0xe1/0x350 2016-09-24T16:43:45.142 controller-1 kernel: warning [90391.023778] [<ffffffff810603c6>] SyS_clone+0x16/0x20 2016-09-24T16:43:45.142 controller-1 kernel: warning [90391.029421] [<ffffffff816792d9>] stub_clone+0x69/0x90 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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