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Reply-To: Gavin Shan <gshan@redhat.com>
Subject: Re: [syzbot] linux-next boot error: WARNING in debug_vm_pgtable
To:     syzbot <syzbot+8730ec44a441a434a2c8@syzkaller.appspotmail.com>,
        akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-next@vger.kernel.org,
        sfr@canb.auug.org.au, syzkaller-bugs@googlegroups.com
References: <00000000000048d99005c7769606@google.com>
From:   Gavin Shan <gshan@redhat.com>
Message-ID: <5e1c2578-c784-9b1e-3033-7d144c4b1e8e@redhat.com>
Date:   Mon, 19 Jul 2021 22:16:29 +1000
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On 7/19/21 7:30 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    08076eab6fef Add linux-next specific files for 20210719
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=16624fd2300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=29a82c885e192046
> dashboard link: https://syzkaller.appspot.com/bug?extid=8730ec44a441a434a2c8
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8730ec44a441a434a2c8@syzkaller.appspotmail.com
> 
> Bluetooth: BNEP filters: protocol multicast
> Bluetooth: BNEP socket layer initialized
> Bluetooth: CMTP (CAPI Emulation) ver 1.0
> Bluetooth: CMTP socket layer initialized
> Bluetooth: HIDP (Human Interface Emulation) ver 1.2
> Bluetooth: HIDP socket layer initialized
> NET: Registered PF_RXRPC protocol family
> Key type rxrpc registered
> Key type rxrpc_s registered
> NET: Registered PF_KCM protocol family
> lec:lane_module_init: lec.c: initialized
> mpoa:atm_mpoa_init: mpc.c: initialized
> l2tp_core: L2TP core driver, V2.0
> l2tp_ppp: PPPoL2TP kernel driver, V2.0
> l2tp_ip: L2TP IP encapsulation support (L2TPv3)
> l2tp_netlink: L2TP netlink interface
> l2tp_eth: L2TP ethernet pseudowire support (L2TPv3)
> l2tp_ip6: L2TP IP encapsulation support for IPv6 (L2TPv3)
> NET: Registered PF_PHONET protocol family
> 8021q: 802.1Q VLAN Support v1.8
> DCCP: Activated CCID 2 (TCP-like)
> DCCP: Activated CCID 3 (TCP-Friendly Rate Control)
> sctp: Hash tables configured (bind 32/56)
> NET: Registered PF_RDS protocol family
> Registered RDS/infiniband transport
> Registered RDS/tcp transport
> tipc: Activated (version 2.0.0)
> NET: Registered PF_TIPC protocol family
> tipc: Started in single node mode
> NET: Registered PF_SMC protocol family
> 9pnet: Installing 9P2000 support
> NET: Registered PF_CAIF protocol family
> NET: Registered PF_IEEE802154 protocol family
> Key type dns_resolver registered
> Key type ceph registered
> libceph: loaded (mon/osd proto 15/24)
> batman_adv: B.A.T.M.A.N. advanced 2021.2 (compatibility version 15) loaded
> openvswitch: Open vSwitch switching datapath
> NET: Registered PF_VSOCK protocol family
> mpls_gso: MPLS GSO support
> IPI shorthand broadcast: enabled
> AVX2 version of gcm_enc/dec engaged.
> AES CTR mode by8 optimization enabled
> sched_clock: Marking stable (13057587730, 27846366)->(13084401149, 1032947)
> registered taskstats version 1
> Loading compiled-in X.509 certificates
> Loaded X.509 cert 'Build time autogenerated kernel key: f850c787ad998c396ae089c083b940ff0a9abb77'
> zswap: loaded using pool lzo/zbud
> debug_vm_pgtable: [debug_vm_pgtable         ]: Validating architecture page table helpers
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1 at mm/page_alloc.c:5349 current_gfp_context include/linux/sched/mm.h:187 [inline]
> WARNING: CPU: 0 PID: 1 at mm/page_alloc.c:5349 __alloc_pages+0x45d/0x500 mm/page_alloc.c:5361
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0-rc2-next-20210719-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__alloc_pages+0x45d/0x500 mm/page_alloc.c:5349
> Code: be c9 00 00 00 48 c7 c7 80 e4 96 89 c6 05 89 1a a5 0b 01 e8 4d ba 35 07 e9 6a ff ff ff 0f 0b e9 a0 fd ff ff 40 80 e5 3f eb 88 <0f> 0b e9 18 ff ff ff 4c 89 ef 44 89 e6 45 31 ed e8 6e 74 ff ff e9
> RSP: 0000:ffffc90000c67b08 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 1ffff9200018cf62 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: 0000000000000012 RDI: 0000000000000cc0
> RBP: 0000000000000000 R08: 000000000000003f R09: 0000000000000003
> R10: ffffffff81b9a5e8 R11: 0000000000000003 R12: 0000000000000012
> R13: 0000000000000012 R14: 0000000000000000 R15: dffffc0000000000
> FS:  0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff88823ffff000 CR3: 000000000b68e000 CR4: 00000000001506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2124
>   alloc_pages+0x26a/0x2d0 mm/mempolicy.c:2274
>   alloc_mem mm/debug_vm_pgtable.c:1138 [inline]
>   debug_vm_pgtable+0x762/0x2986 mm/debug_vm_pgtable.c:1169
>   do_one_initcall+0x103/0x650 init/main.c:1285
>   do_initcall_level init/main.c:1360 [inline]
>   do_initcalls init/main.c:1376 [inline]
>   do_basic_setup init/main.c:1396 [inline]
>   kernel_init_freeable+0x6b8/0x741 init/main.c:1598
>   kernel_init+0x1a/0x1d0 init/main.c:1490
>   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 

This was caused by allocating pages more than (1 << (MAX_ORDER - 1)) in
mm/debug_vm_pgtable.c::alloc_mem() in v1 series. I will fix it in v3 to
skip the allocation if the requested size is more than (1 << (MAX_ORDER - 1))
in v3.

> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 

Thanks,
Gavin