Re: [uml-devel] [PATCH] correct gid in hostfs_kern.c

[Blaisorblade <blaisorblade@yahoo.it>]

On Tuesday 23 September 2003 19:20, Hannes Schulz wrote:
> I was reading hostfs_* because I wanted hostfs as rootfs (when
> launched by root).

> --- uml-2.4.22um5-orig/arch/um/fs/hostfs/hostfs_kern.c 2003-09-23
> 15:21:33.000000000 +0200
> +++ uml-2.4.22um5-hwh1/arch/um/fs/hostfs/hostfs_kern.c 2003-09-23
> 15:24:42.000000000 +0200
> @@ -766,7 +766,7 @@
>    if(attr->ia_valid & ATTR_GID){
>     if(kdev_same(dentry->d_inode->i_sb->s_dev, ROOT_DEV) &&
>        (attr->ia_gid == 0))
> -   attr->ia_gid = getuid();
> +   attr->ia_gid = getgid();
>     attrs.ia_valid |= HOSTFS_ATTR_GID;
>     attrs.ia_gid = attr->ia_gid;
>    }

I've verified that this patch has not yet been applied, neither in 2.4 nor in 
2.6. I'm going to merge it into 2.6.11.

The original code does not make sense (since a given UID could not exist as a 
GID) so it *must* be a typo, and not done on purpose.

I don't understand the purpose of the patched branch, however... it means that 
chgrp 0 "fileName" will be executed as chgrp <group as UML is running> 
fileName.

And only when running hostfs as rootfs.... well, it makes sense since when 
stat()'ing a file this code is used:

        if((ino->i_sb->s_dev == ROOT_DEV) && (ino->i_uid == getuid()))
                ino->i_uid = 0;

i.e. if UML runs as uid 500, the host uid 500 is mapped to the guest uid 0. 
This does not happen for the gids, which is to fix.

Also, these two threads deserve a look, too:

[uml-devel] [PATCH] hostfs as root (when lauched by root)
[uml-devel] [BUG 2.4.22-um5 + hostfs] file not updated upon munmap

-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade




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