Mount failure caused by colon/comma characters in the path of lower/upper dirs

Mount failure caused by colon/comma characters in the path of lower/upper dirs

[Chengguang Xu]

Hello,

Today I got a mount failure report from a docker developer about special characters in overlayfs lower/upper path.
The root cause is quite straightforward  because overlayfs uses colon/comma as seperator of lowerdir layers and module options.
However, Colon/Comma characters are valid for directory name on linux so some people(especially container users) hope overlayfs
could correctly recognize and handle those directories.

Strengthen option parsing seems a right solution for fixing the issue, what do think for this?



Thanks,
Chengguang Xu

Re: Mount failure caused by colon/comma characters in the path of lower/upper dirs

[Miklos Szeredi]

On Tue, 22 Jun 2021 at 18:30, Chengguang Xu <cgxu519@mykernel.net> wrote:
>
> Hello,
>
> Today I got a mount failure report from a docker developer about special characters in overlayfs lower/upper path.
> The root cause is quite straightforward  because overlayfs uses colon/comma as seperator of lowerdir layers and module options.
> However, Colon/Comma characters are valid for directory name on linux so some people(especially container users) hope overlayfs
> could correctly recognize and handle those directories.
>
> Strengthen option parsing seems a right solution for fixing the issue, what do think for this?

Use backslash as an escape character.  E.g. lower directory named
"ab,cd:ef" needs to be passed to mount as "-olowerdir=ab\,cd\:ef"

Thanks,
Miklos

Re: Mount failure caused by colon/comma characters in the path of lower/upper dirs

[Chengguang Xu]

---- 在 星期五, 2021-07-09 22:03:11 Miklos Szeredi <miklos@szeredi.hu> 撰写 ----
 > On Tue, 22 Jun 2021 at 18:30, Chengguang Xu <cgxu519@mykernel.net> wrote:
 > >
 > > Hello,
 > >
 > > Today I got a mount failure report from a docker developer about special characters in overlayfs lower/upper path.
 > > The root cause is quite straightforward  because overlayfs uses colon/comma as seperator of lowerdir layers and module options.
 > > However, Colon/Comma characters are valid for directory name on linux so some people(especially container users) hope overlayfs
 > > could correctly recognize and handle those directories.
 > >
 > > Strengthen option parsing seems a right solution for fixing the issue, what do think for this?
 > 
 > Use backslash as an escape character.  E.g. lower directory named
 > "ab,cd:ef" needs to be passed to mount as "-olowerdir=ab\,cd\:ef"
 > 

Hi Miklos,

Thanks for your advice, it worked well.
Minor fix is "ab,cd:ef" needs to be passed to mount as "-olowerdir=ab\\,cd\\:ef"


Thanks,
Chengguang