Re: [uml-devel] hostfs permissions

[Karl Chen <quarl@cs.berkeley.edu>]

>>>>> On 2005-06-10 15:26 PDT, Blaisorblade  writes:

    Blaisorblade> Ok, in this case there's probably a simpler
    Blaisorblade> road: simply use a 2.4.27-1bs kernel. The
    Blaisorblade> implemented behaviour is that all created files
    Blaisorblade> will have the ID they have on the host, i.e. the
    Blaisorblade> ID of the user running UML.

Thanks for the tip!  I will be running UML under different user
IDs but I'd rather it always be the same uid inside the UML.  I
used this micropatch to get exactly the behavior I want.  It's
obviously for this particular experiment only; I still think
uid,gid mount options would be better in general.  I guess that's
only 5 or 10 more lines of code...


diff -u /home/quarl/proj/uml/linux/linux-2.4.27/arch/um/fs/hostfs/.backup/hostfs_kern.c.\~1\~ /home/quarl/proj/uml/linux/linux-2.4.27/arch/um/fs/hostfs/hostfs_kern.c
--- /home/quarl/proj/uml/linux/linux-2.4.27/arch/um/fs/hostfs/.backup/hostfs_kern.c.~1~	2005-06-10 16:58:51.000000000 -0700
+++ /home/quarl/proj/uml/linux/linux-2.4.27/arch/um/fs/hostfs/hostfs_kern.c	2005-06-10 17:35:01.829485585 -0700
@@ -1,3 +1,6 @@
+#define KLUDGE_FS_UID 7777
+#define KLUDGE_FS_GID 7777
+
 /*
  * Copyright (C) 2000 - 2003 Jeff Dike (jdike@addtoit.com)
  * Licensed under the GPL
@@ -142,6 +145,10 @@
 	ino->i_blocks = i_blocks;
 	if(kdev_same(ino->i_sb->s_dev, ROOT_DEV) && (ino->i_uid == getuid()))
 		ino->i_uid = 0;
+        else if (ino->i_uid == getuid()) {          /* KC KLUDGE */
+                ino->i_uid = KLUDGE_FS_UID;         /* KC KLUDGE */
+                ino->i_gid = KLUDGE_FS_GID;         /* KC KLUDGE */
+        }                                           /* KC KLUDGE */
 	return(0);
 }
 
@@ -760,13 +767,17 @@
 		if(kdev_same(dentry->d_inode->i_sb->s_dev, ROOT_DEV) &&
 		   (attr->ia_uid == 0))
 			attr->ia_uid = getuid();
+                else if (attr->ia_uid == KLUDGE_FS_UID) { /* KC KLUDGE */
+                        attr->ia_uid = getuid();          /* KC KLUDGE */
+                        attr->ia_gid = getgid();          /* KC KLUDGE */
+                }                                         /* KC KLUDGE */
 		attrs.ia_valid |= HOSTFS_ATTR_UID;
 		attrs.ia_uid = attr->ia_uid;
 	}
 	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;
 	}


-- 
Karl 2005-06-10 17:44


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