linux-kernel - Re: [syzbot] upstream boot error: BUG: unable to handle kernel NULL pointer dereference in corrupted

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Message-ID: <CACT4Y+YgaKVMqAT_qjZjFCWnSSJ=EU4fk1cue7RLsmS7p1H2AQ@mail.gmail.com>
Date:   Tue, 2 May 2023 08:50:22 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+0f3348b0cb4da6b6072d@...kaller.appspotmail.com>
Cc:     linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [syzbot] upstream boot error: BUG: unable to handle kernel NULL
 pointer dereference in corrupted

On Fri, 28 Apr 2023 at 22:52, syzbot
<syzbot+0f3348b0cb4da6b6072d@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    22b8cc3e78f5 Merge tag 'x86_mm_for_6.4' of git://git.kerne..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11fa5010280000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1af34c4cafb72074
> dashboard link: https://syzkaller.appspot.com/bug?extid=0f3348b0cb4da6b6072d
> compiler:       arm-linux-gnueabi-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: arm
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0f3348b0cb4da6b6072d@...kaller.appspotmail.com

+arm mailing list

Kernel started falling apart on arm during boot in various strange ways.

#syz set subsystems: arm

> Movable zone start for each node
> Early memory node ranges
>   node   0: [mem 0x0000000080000000-0x00000000ffffffff]
> Initmem setup node 0 [mem 0x0000000080000000-0x00000000ffffffff]
> percpu: Embedded 19 pages/cpu s47048 r8192 d22584 u77824
> Kernel command line: root=/dev/vda console=ttyAMA0  earlyprintk=serial net.ifnames=0 sysctl.kernel.hung_task_all_cpu_backtrace=1 ima_policy=tcb nf-conntrack-ftp.ports=20000 nf-conntrack-tftp.ports=20000 nf-conntrack-sip.ports=20000 nf-conntrack-irc.ports=20000 nf-conntrack-sane.ports=20000 binder.debug_mask=0 rcupdate.rcu_expedited=1 rcupdate.rcu_cpu_stall_cputime=1 no_hash_pointers page_owner=on sysctl.vm.nr_hugepages=4 sysctl.vm.nr_overcommit_hugepages=4 secretmem.enable=1 sysctl.max_rcu_stall_to_panic=1 msr.allow_writes=off coredump_filter=0xffff root=/dev/vda console=ttyAMA0 vmalloc=512M smp.csd_lock_timeout=300000 watchdog_thresh=165 workqueue.watchdog_thresh=420 sysctl.net.core.netdev_unregister_timeout_secs=420 dummy_hcd.num=2 panic_on_warn=1
> Unknown kernel command line parameters "earlyprintk=serial page_owner=on", will be passed to user space.
> Dentry cache hash table entries: 262144 (order: 8, 1048576 bytes, linear)
> Inode-cache hash table entries: 131072 (order: 7, 524288 bytes, linear)
> Built 1 zonelists, mobility grouping on.  Total pages: 520868
> allocated 2097152 bytes of page_ext
> mem auto-init: stack:off, heap alloc:on, heap free:off
> software IO TLB: area num 2.
> software IO TLB: mapped [mem 0x00000000d9a47000-0x00000000dda47000] (64MB)
> Memory: 1954368K/2097152K available (22528K kernel code, 2361K rwdata, 8400K rodata, 2048K init, 867K bss, 126400K reserved, 16384K cma-reserved, 524288K highmem)
> SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
> trace event string verifier disabled
> rcu: Preemptible hierarchical RCU implementation.
> rcu:    RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=2.
> rcu:    RCU callback double-/use-after-free debug is enabled.
>         All grace periods are expedited (rcu_expedited).
>         Trampoline variant of Tasks RCU enabled.
>         Tracing variant of Tasks RCU enabled.
> rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies.
> rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=2
> NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
> GIC physical location is 0x2c001000
> rcu: srcu_init: Setting srcu_struct sizes based on contention.
> sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns
> clocksource: arm,sp804: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275 ns
> arch_timer: cp15 timer(s) running at 62.50MHz (virt).
> clocksource: arch_sys_counter: mask: 0x1ffffffffffffff max_cycles: 0x1cd42e208c, max_idle_ns: 881590405314 ns
> sched_clock: 57 bits at 63MHz, resolution 16ns, wraps every 4398046511096ns
> Switching to timer-based delay loop, resolution 16ns
> Console: colour dummy device 80x30
> Calibrating delay loop (skipped), value calculated using timer frequency.. 125.00 BogoMIPS (lpj=625000)
> pid_max: default: 32768 minimum: 301
> LSM: initializing lsm=lockdown,capability,landlock,yama,safesetid,tomoyo,selinux,bpf,integrity
> landlock: Up and running.
> Yama: becoming mindful.
> TOMOYO Linux initialized
> SELinux:  Initializing.
> LSM support for eBPF active
> stackdepot: allocating hash table of 131072 entries via kvcalloc
> Mount-cache hash table entries: 4096 (order: 2, 16384 bytes, linear)
> Mountpoint-cache hash table entries: 4096 (order: 2, 16384 bytes, linear)
> CPU: Testing write buffer coherency: ok
> CPU0: Spectre BHB: enabling loop workaround for all CPUs
> CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
> 8<--- cut here ---
> Unable to handle kernel NULL pointer dereference at virtual address 00000206 when execute
> [00000206] *pgd=80000080004003, *pmd=00000000
>
>
> ---
> 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@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the bug is already fixed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want to change bug's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the bug is a duplicate of another bug, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
>
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