[uml-devel] [patch 6/8] uml: fix hostfs special perm handling [for 2.6.12]

[uml-devel] [patch 6/8] uml: fix hostfs special perm handling [for 2.6.12]

[blaisorblade]

From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
CC: Rob Landley <rob@landley.net>
When opening devices nodes on hostfs, it does not make sense to call
access(), since we are not going to open the file on the host.

If the device node is owned by root, the root user in UML should succeed in
opening it, even if UML won't be able to open the file.

As reported by Rob Landley, UML currently does not follow this, so here's an
(untested) fix.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
---

 linux-2.6.11-paolo/fs/hostfs/hostfs_kern.c |   20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diff -puN fs/hostfs/hostfs_kern.c~uml-fix-hostfs-special-perm-handling fs/hostfs/hostfs_kern.c
--- linux-2.6.11/fs/hostfs/hostfs_kern.c~uml-fix-hostfs-special-perm-handling	2005-03-22 20:10:07.000000000 +0100
+++ linux-2.6.11-paolo/fs/hostfs/hostfs_kern.c	2005-03-22 20:12:45.000000000 +0100
@@ -806,15 +806,21 @@ int hostfs_permission(struct inode *ino,
 	char *name;
 	int r = 0, w = 0, x = 0, err;
 
-	if(desired & MAY_READ) r = 1;
-	if(desired & MAY_WRITE) w = 1;
-	if(desired & MAY_EXEC) x = 1;
+	if (desired & MAY_READ) r = 1;
+	if (desired & MAY_WRITE) w = 1;
+	if (desired & MAY_EXEC) x = 1;
 	name = inode_name(ino, 0);
-	if(name == NULL) return(-ENOMEM);
-	err = access_file(name, r, w, x);
+	if (name == NULL) return(-ENOMEM);
+
+	if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
+			S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
+		err = 0;
+	else
+		err = access_file(name, r, w, x);
 	kfree(name);
-	if(!err) err = generic_permission(ino, desired, NULL);
-	return(err);
+	if(!err)
+		err = generic_permission(ino, desired, NULL);
+	return err;
 }
 
 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
_


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[uml-devel] Re: [patch 6/8] uml: fix hostfs special perm handling [for 2.6.12]

[Rob Landley]

On Wednesday 30 March 2005 12:34 pm, blaisorblade@yahoo.it wrote:
> From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
> CC: Rob Landley <rob@landley.net>
> When opening devices nodes on hostfs, it does not make sense to call
> access(), since we are not going to open the file on the host.
>
> If the device node is owned by root, the root user in UML should succeed in
> opening it, even if UML won't be able to open the file.
>
> As reported by Rob Landley, UML currently does not follow this, so here's
> an (untested) fix.
>
> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

Not untested, it Worked For Me (tm).

Signed-off-by: Rob Landley <rob@landley.net>

> ---
>
>  linux-2.6.11-paolo/fs/hostfs/hostfs_kern.c |   20 +++++++++++++-------
>  1 files changed, 13 insertions(+), 7 deletions(-)
>
> diff -puN fs/hostfs/hostfs_kern.c~uml-fix-hostfs-special-perm-handling
> fs/hostfs/hostfs_kern.c ---
> linux-2.6.11/fs/hostfs/hostfs_kern.c~uml-fix-hostfs-special-perm-handling	2
>005-03-22 20:10:07.000000000 +0100 +++
> linux-2.6.11-paolo/fs/hostfs/hostfs_kern.c	2005-03-22 20:12:45.000000000
> +0100 @@ -806,15 +806,21 @@ int hostfs_permission(struct inode *ino,
>  	char *name;
>  	int r = 0, w = 0, x = 0, err;
>
> -	if(desired & MAY_READ) r = 1;
> -	if(desired & MAY_WRITE) w = 1;
> -	if(desired & MAY_EXEC) x = 1;
> +	if (desired & MAY_READ) r = 1;
> +	if (desired & MAY_WRITE) w = 1;
> +	if (desired & MAY_EXEC) x = 1;
>  	name = inode_name(ino, 0);
> -	if(name == NULL) return(-ENOMEM);
> -	err = access_file(name, r, w, x);
> +	if (name == NULL) return(-ENOMEM);
> +
> +	if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
> +			S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
> +		err = 0;
> +	else
> +		err = access_file(name, r, w, x);
>  	kfree(name);
> -	if(!err) err = generic_permission(ino, desired, NULL);
> -	return(err);
> +	if(!err)
> +		err = generic_permission(ino, desired, NULL);
> +	return err;
>  }
>
>  int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
> _


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