Re: [PATCH] fs: improve dump_mapping() robustness

[Baolin Wang]

On 1/16/2024 7:16 PM, Christian Brauner wrote:
> On Tue, 16 Jan 2024 15:53:35 +0800, Baolin Wang wrote:
> > We met a kernel crash issue when running stress-ng testing, and the
> > system crashes when printing the dentry name in dump_mapping().
> >
> > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> > pc : dentry_name+0xd8/0x224
> > lr : pointer+0x22c/0x370
> > sp : ffff800025f134c0
> > ......
> > Call trace:
> >    dentry_name+0xd8/0x224
> >    pointer+0x22c/0x370
> >    vsnprintf+0x1ec/0x730
> >    vscnprintf+0x2c/0x60
> >    vprintk_store+0x70/0x234
> >    vprintk_emit+0xe0/0x24c
> >    vprintk_default+0x3c/0x44
> >    vprintk_func+0x84/0x2d0
> >    printk+0x64/0x88
> >    __dump_page+0x52c/0x530
> >    dump_page+0x14/0x20
> >    set_migratetype_isolate+0x110/0x224
> >    start_isolate_page_range+0xc4/0x20c
> >    offline_pages+0x124/0x474
> >    memory_block_offline+0x44/0xf4
> >    memory_subsys_offline+0x3c/0x70
> >    device_offline+0xf0/0x120
> >    ......
> >
> > [...]
>
> Seems fine for debugging purposes. Let me know if this needs to go through
> somewhere else.

Going through VFS tree is fine to me. Thanks.