Re: [syzbot] BUG: sleeping function called from invalid context in break_ksm

[David Hildenbrand]

On 20.10.22 14:59, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    acee3e83b493 Add linux-next specific files for 20221020
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15961f62880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c82245cfb913f766
> dashboard link: https://syzkaller.appspot.com/bug?extid=78a0878b3076f71313b3
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1255612c880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12a1bed2880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/98cc5896cded/disk-acee3e83.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b3d3eb3aa10a/vmlinux-acee3e83.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+78a0878b3076f71313b3@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> BUG: sleeping function called from invalid context at mm/ksm.c:500
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 3610, name: syz-executor212
> preempt_count: 1, expected: 0
> RCU nest depth: 0, expected: 0
> INFO: lockdep is turned off.
> Preemption disabled at:
> [<0000000000000000>] 0x0
> CPU: 0 PID: 3610 Comm: syz-executor212 Not tainted 6.1.0-rc1-next-20221020-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> Call Trace:
>   <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>   __might_resched.cold+0x222/0x26b kernel/sched/core.c:9890
>   break_ksm.part.0+0xbe/0x160 mm/ksm.c:500
>   break_ksm mm/ksm.c:875 [inline]
>   unmerge_ksm_pages+0x1a0/0x240 mm/ksm.c:881
>   unmerge_and_remove_all_rmap_items mm/ksm.c:1021 [inline]
>   run_store+0x3cf/0xa30 mm/ksm.c:2983
>   kobj_attr_store+0x50/0x80 lib/kobject.c:824
>   sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:136
>   kernfs_fop_write_iter+0x3f8/0x610 fs/kernfs/file.c:330
>   call_write_iter include/linux/fs.h:2191 [inline]
>   new_sync_write fs/read_write.c:491 [inline]
>   vfs_write+0x9e9/0xdd0 fs/read_write.c:584
>   ksys_write+0x127/0x250 fs/read_write.c:637
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd


This might be due a missing page table lock unlock:

https://lkml.kernel.org/r/8c86678a-3bfb-3854-b1a9-ae5969e730b8@xxxxxxxxxx

--
Thanks,

David / dhildenb