Re: [Bug 202149] New: NULL Pointer Dereference in __split_huge_pmd on PPC64LE

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On Fri, 04 Jan 2019 22:49:52 +0000 bugzilla-daemon@bugzilla.kernel.org wrote:

https://bugzilla.kernel.org/show_bug.cgi?id=202149

            Bug ID: 202149
           Summary: NULL Pointer Dereference in __split_huge_pmd on
                    PPC64LE

I think that trace is pointing at the ppc-specific
pgtable_trans_huge_withdraw()?

           Product: Memory Management
           Version: 2.5
    Kernel Version: 4.19.13
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Other
          Assignee: akpm@linux-foundation.org
          Reporter: kernel@bluematt.me
        Regression: No

Kernel is actually 4.19.13 + this commit to fix mpt3sas, though I also saw this
fault with a different version of mpt3sas patched into an earlier 4.19 kernel
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=23c3828aa2f84edec7020c7397a22931e7a879e1
. Config is roughly Debian's default config + 4K pages instead of the default
64K.

[ 9531.579895] Unable to handle kernel paging request for data at address
0x00000000
[ 9531.579918] Faulting instruction address: 0xc000000000076c64
[ 9531.579930] Oops: Kernel access of bad area, sig: 11 [#1]
[ 9531.579948] LE SMP NR_CPUS=2048 NUMA PowerNV
[ 9531.579960] Modules linked in: binfmt_misc veth xt_nat tap
nft_chain_nat_ipv4 nft_chain_route_ipv4 tun btrfs zstd_compress zstd_decompress
xxhash ipip tunnel4 ip_tunnel ipt_MASQUERADE nf_nat_ipv4 nf_nat nf_conntrack
nf_defrag_ipv6 nf_defrag_ipv4 xt_DSCP xt_dscp nft_counter xt_tcpudp nft_compat
nf_tables nfnetlink amdgpu chash gpu_sched ast snd_hda_codec_hdmi ttm
drm_kms_helper snd_hda_intel snd_hda_codec drm sg snd_hda_core snd_hwdep
snd_pcm uas drm_panel_orientation_quirks syscopyarea sysfillrect snd_timer
sysimgblt fb_sys_fops tg3 mpt3sas snd i2c_algo_bit ofpart ipmi_powernv opal_prd
ipmi_devintf soundcore ipmi_msghandler powernv_flash libphy mtd raid_class
scsi_transport_sas at24 ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2
fscrypto sd_mod raid10 raid456 crc32c_generic libcrc32c async_raid6_recov
[ 9531.580142]  async_memcpy async_pq evdev hid_generic usbhid hid raid6_pq
async_xor xor async_tx raid1 raid0 multipath linear md_mod usb_storage dm_crypt
dm_mod algif_skcipher af_alg ecb xts xhci_pci vmx_crypto xhci_hcd usbcore nvme
nvme_core usb_common
[ 9531.580219] CPU: 9 PID: 4762 Comm: rustc Not tainted 4.19.0-2-powerpc64le #1
Debian 4.19.13-1
[ 9531.580250] NIP:  c000000000076c64 LR: c00000000037ec38 CTR:
c0000000000471e0
[ 9531.580280] REGS: c0000001a4f6f840 TRAP: 0300   Not tainted 
(4.19.0-2-powerpc64le Debian 4.19.13-1)
[ 9531.580311] MSR:  9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE>  CR: 24202848 
XER: 00000000
[ 9531.580337] CFAR: c00000000037ec34 DAR: 0000000000000000 DSISR: 40000000
IRQMASK: 0 
               GPR00: c00000000037ec38 c0000001a4f6fac0 c0000000010a5800
c0000008b1a2ec00 
               GPR04: c0000001a0ccaf80 0000000000000800 c000000001202e60
c000000001202de0 
               GPR08: 0000000000000009 c00a000006833280 c00a000000000000
c0000000010b9fd8 
               GPR12: 0000000000002000 c000000fffff9600 00003fff40000000
0001000000000000 
               GPR16: e61fffffffffffff fffffffffffffe7f 0000000000000001
c00a0000065f48a8 
               GPR20: c0000001a0ccaf80 0002000000000000 c0000008b1a2ec00
c000000001202de0 
               GPR24: c00a000019a20000 c0000008b1a2ec00 c0000001a0ccaf80
c0000006f001c5b0 
               GPR28: c00a000006833280 c000000001202e68 00003fff3e000000
0000000000000000 
[ 9531.580483] NIP [c000000000076c64]
radix__pgtable_trans_huge_withdraw+0x94/0x160
[ 9531.580506] LR [c00000000037ec38] __split_huge_pmd+0x588/0xcc0
[ 9531.580524] Call Trace:
[ 9531.580541] [c0000001a4f6fac0] [c0000001a4f6fb10] 0xc0000001a4f6fb10
(unreliable)
[ 9531.580572] [c0000001a4f6faf0] [c00000000037ebbc]
__split_huge_pmd+0x50c/0xcc0
[ 9531.580605] [c0000001a4f6fbb0] [c00000000032aeb8]
move_page_tables+0x438/0xd30
[ 9531.580637] [c0000001a4f6fcc0] [c00000000032b8fc] move_vma+0x14c/0x370
[ 9531.580669] [c0000001a4f6fd60] [c00000000032c0a8] sys_mremap+0x588/0x670
[ 9531.580702] [c0000001a4f6fe30] [c00000000000b9e4] system_call+0x5c/0x70
[ 9531.580732] Instruction dump:
[ 9531.580760] 0b0a0000 e9060000 e9470000 7d294030 7d2907b4 79291f24 7d2900d0
7d292038 
[ 9531.580797] 7929a402 79293664 7d2a4a14 ebe90010 <e95f0000> 7fbf5040 419e0064
7c0802a6 
[ 9531.580837] ---[ end trace 21ba871647464d8b ]---

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