Subject: next-20230720: BUG: kernel NULL pointer dereference

From: "Aithal, Srikanth" <[email-masked]>
Date: Fri, 21 Jul 2023 09:16:17 +0530

Hello all,

Linux next build next-20230720 hits BUG: kernel NULL pointer dereference 
while booting SEV guest:

===============
Recreation steps
===============
1. Run shutdown tests for around 10 times with SVM guest having around 
85% of Host RAM [note: nothing else is running on host as well as inside 
guest].
2. Then try to boot a SEV guest with 85% of Host RAM, we hit below call 
trace:

===============
Call trace:
===============
[  775.069108] BUG: kernel NULL pointer dereference, address: 
0000000000000498
[  775.076069] #PF: supervisor read access in kernel mode
[  775.081200] #PF: error_code(0x0000) - not-present page
[  775.086329] PGD 0 P4D 0
[  775.088861] Oops: 0000 [#1] PREEMPT SMP NOPTI
[  775.093211] CPU: 45 PID: 796 Comm: kcompactd1 Kdump: loaded Not 
tainted 6.5.0-rc2-next-20230720-next-20230720- #1
[  775.103465] Hardware name: Dell Inc. PowerEdge R6515/07PXPY, BIOS 
2.8.5 08/18/2022
[  775.111029] RIP: 0010:arch_tlbbatch_flush+0xcf/0x130
[  775.115995] Code: 48 83 c2 3f 48 c1 ea 06 48 c1 e2 03 e8 3a 17 e1 00 
65 ff 0d 2b b6 38 4e 74 5b 65 48 8b 04 25 40 2e 03 00 48 8b b8 e0 08 00 
00 <48> 83 bf 98 04 00 00 00 75 31 5b 41 5c 41 5d 41 5e 5d c3 cc cc cc
[  775.134732] RSP: 0018:ffffb4a20e7aba58 EFLAGS: 00010286
[  775.139949] RAX: ffff974907fd3300 RBX: 000000000000002d RCX: 
0000000000000000
[  775.147073] RDX: 0000000000000010 RSI: 0000000000000000 RDI: 
0000000000000000
[  775.154197] RBP: ffffb4a20e7aba78 R08: 0000000000000080 R09: 
ffff974907fd4220
[  775.161322] R10: 0000000000000002 R11: 0000000000000002 R12: 
ffff974907fd4220
[  775.168454] R13: ffff9787d6372f80 R14: 000000000000002e R15: 
ffffb4a20e7abc80
[  775.175577] FS:  0000000000000000(0000) GS:ffff9787d6340000(0000) 
knlGS:0000000000000000
[  775.183654] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  775.189392] CR2: 0000000000000498 CR3: 0008003cca62e003 CR4: 
0000000000770ee0
[  775.196517] PKRU: 55555554
[  775.199227] Call Trace:
[  775.201672]  <TASK>
[  775.203771]  ? show_regs+0x6e/0x80
[  775.207174]  ? __die+0x29/0x70
[  775.210224]  ? page_fault_oops+0x160/0x460
[  775.214315]  ? __mod_lruvec_page_state+0xa4/0x150
[  775.219012]  ? page_vma_mapped_walk+0xfd/0x8e0
[  775.223450]  ? page_remove_rmap+0xac/0x250
[  775.227540]  ? do_user_addr_fault+0x306/0x690
[  775.231900]  ? exc_page_fault+0x7d/0x190
[  775.235825]  ? asm_exc_page_fault+0x2b/0x30
[  775.240003]  ? arch_tlbbatch_flush+0xcf/0x130
[  775.244352]  ? arch_tlbbatch_flush+0xb6/0x130
[  775.248705]  try_to_unmap_flush+0x2c/0x40
[  775.252716]  migrate_pages_batch+0x678/0xbe0
[  775.256989]  ? __pfx_compaction_free+0x10/0x10
[  775.261435]  ? __pfx_compaction_alloc+0x10/0x10
[  775.265958]  migrate_pages+0x9be/0xc50
[  775.269702]  ? cgroup_rstat_updated+0xc4/0xe0
[  775.274063]  ? __mod_lruvec_state+0x3b/0x50
[  775.278238]  ? __pfx_compaction_free+0x10/0x10
[  775.282677]  ? __pfx_compaction_alloc+0x10/0x10
[  775.287203]  compact_zone+0x7a8/0xef0
[  775.290866]  ? psi_task_switch+0xd9/0x240
[  775.294879]  ? finish_task_switch.isra.0+0x85/0x290
[  775.299759]  proactive_compact_node+0x88/0xe0
[  775.304118]  kcompactd+0x37a/0x400
[  775.307514]  ? __pfx_autoremove_wake_function+0x10/0x10
[  775.312740]  ? __pfx_kcompactd+0x10/0x10
[  775.316658]  kthread+0xfb/0x130
[  775.319803]  ? __pfx_kthread+0x10/0x10
[  775.323547]  ret_from_fork+0x40/0x60
[  775.327127]  ? __pfx_kthread+0x10/0x10
[  775.330870]  ret_from_fork_asm+0x1b/0x30
[  775.334798]  </TASK>
[  775.336988] Modules linked in: xt_CHECKSUM xt_MASQUERADE xt_conntrack 
ipt_REJECT xt_tcpudp nft_compat x_tables nf_nat_tftp nf_conntrack_tftp 
bridge stp llc ib_core nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib 
nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct 
nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set 
nf_tables nfnetlink sunrpc nls_iso8859_1 ipmi_ssif intel_rapl_msr 
intel_rapl_common amd64_edac kvm_amd kvm acpi_ipmi ipmi_si rapl 
ipmi_devintf joydev wmi_bmof input_leds pcspkr efi_pstore i2c_piix4 
k10temp ipmi_msghandler acpi_power_meter evbug mac_hid sch_fq_codel xfs 
libcrc32c hid_generic usbkbd usbmouse usbhid hid mgag200 drm_kms_helper 
i2c_algo_bit drm_shmem_helper drm crct10dif_pclmul crc32_pclmul 
ghash_clmulni_intel sha512_ssse3 aesni_intel mpt3sas crypto_simd cryptd 
tg3 ccp raid_class scsi_transport_sas sp5100_tco wmi dm_mirror 
dm_region_hash dm_log msr autofs4
[  775.417215] CR2: 0000000000000498
[  775.420532] ---[ end trace 0000000000000000 ]---
[  775.504479] pstore: backend (erst) writing error (-28)
[  775.509615] RIP: 0010:arch_tlbbatch_flush+0xcf/0x130
[  775.514581] Code: 48 83 c2 3f 48 c1 ea 06 48 c1 e2 03 e8 3a 17 e1 00 
65 ff 0d 2b b6 38 4e 74 5b 65 48 8b 04 25 40 2e 03 00 48 8b b8 e0 08 00 
00 <48> 83 bf 98 04 00 00 00 75 31 5b 41 5c 41 5d 41 5e 5d c3 cc cc cc
[  775.533326] RSP: 0018:ffffb4a20e7aba58 EFLAGS: 00010286
[  775.538543] RAX: ffff974907fd3300 RBX: 000000000000002d RCX: 
0000000000000000
[  775.545666] RDX: 0000000000000010 RSI: 0000000000000000 RDI: 
0000000000000000
[  775.552789] RBP: ffffb4a20e7aba78 R08: 0000000000000080 R09: 
ffff974907fd4220
[  775.559914] R10: 0000000000000002 R11: 0000000000000002 R12: 
ffff974907fd4220
[  775.567039] R13: ffff9787d6372f80 R14: 000000000000002e R15: 
ffffb4a20e7abc80
[  775.574162] FS:  0000000000000000(0000) GS:ffff9787d6340000(0000) 
knlGS:0000000000000000
[  775.582238] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  775.587978] CR2: 0000000000000498 CR3: 0008003cca62e003 CR4: 
0000000000770ee0
[  775.595109] PKRU: 55555554
[  775.597814] note: kcompactd1[796] exited with irqs disabled