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

[Christian Brauner]

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.

---

Applied to the vfs.misc branch of the vfs/vfs.git tree.
Patches in the vfs.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.misc

[1/1] fs: improve dump_mapping() robustness
      https://git.kernel.org/vfs/vfs/c/30a1b9d12728