[uml-devel] 2.4 hostfs no longer mounts specified directoryy

[uml-devel] 2.4 hostfs no longer mounts specified directoryy

[Henrik Nordstrom]

Something seems to have changed in how hostfs parses the filesystem flags
option.  It no longer succeeds in specifying the location of the hostfs
directory and the uml instead always uses the host root (/).

Neither rootflags=/... for booting from hostfs or manual mount works. In 
both cases it always gives the host root (/), not the specified directory.

Using the current 2.4 CVS, ported to 2.4.26.

Was previously using the almost current 2.4 CVS (before humfs), ported to 
2.4.26-rc2 with no problem.

Regards
Henrik



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[uml-devel] [patch] 2.4 hostfs no longer mounts specified directory

[Henrik Nordstrom]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1254 bytes --]

The attached patch fixes a number of hostfs problems in the current 2.4 
tree. With this patch hostfs again has the same capabilities as before the 
addition of humfs.

  * Use the specified host directory like was done earlier, not hardcoded
to "/"
  * Allocate the root directory name. The mount flags is freed by the 
kernel.
  * host_file.c was missing #include <string.h> (uses strlen, memcpy 
etc..) (gcc warnings)
  * make all hostfs files owned by root (uid=0), not file owner on the
host.


Todo:

  - Give hostfs a real mount structure in the kernel superblock like humfs
has, allowing for storage of various mount flags and not only a root path.
  - uid= mount flag to specify what uid the filesystem should be mounted 
as inside the uml. [depends on the above]
  - use "nobody" as uid if the host file uid is different from the host 
uid running the uml. [almost a oneliner, independent of the above but 
touches the same area]

Notes:

  - The hostfs "jail" option is not very secure in combination with the 
ability to specify a root path. One can easily use .. or symlinks to 
subvert this. The ability to specify a root path should maybe be disabled 
if a jail path is specified. Chrooting would be a much better option.


Regards
Henrik

[-- Attachment #2: Type: TEXT/PLAIN, Size: 6368 bytes --]

Index: arch/um/fs/hostfs/host_file.c
===================================================================
RCS file: /cvsroot/user-mode-linux/linux/arch/um/fs/hostfs/host_file.c,v
retrieving revision 1.1
diff -u -p -r1.1 host_file.c
--- arch/um/fs/hostfs/host_file.c	7 Apr 2004 20:44:01 -0000	1.1
+++ arch/um/fs/hostfs/host_file.c	24 Apr 2004 10:56:19 -0000
@@ -11,6 +11,7 @@
 #include <dirent.h>
 #include <utime.h>
 #include <sys/vfs.h>
+#include <string.h>
 #include "os.h"
 #include "user.h"
 #include "hostfs.h"
Index: arch/um/fs/hostfs/hostfs_user.c
===================================================================
RCS file: /cvsroot/user-mode-linux/linux/arch/um/fs/hostfs/hostfs_user.c,v
retrieving revision 1.23
diff -u -p -r1.23 hostfs_user.c
--- arch/um/fs/hostfs/hostfs_user.c	7 Apr 2004 20:44:02 -0000	1.23
+++ arch/um/fs/hostfs/hostfs_user.c	24 Apr 2004 10:56:19 -0000
@@ -62,7 +62,7 @@ __uml_setup("hostfs=", hostfs_args,
 static int access_file(char *file, int uid, int gid, int r, int w, int x, 
 		       void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 	char tmp[HOSTFS_BUFSIZE];
 	int err, mode = 0;
 
@@ -88,7 +88,7 @@ static int mk_nod(const char *file, int 
 		  int gr, int gw, int gx, int or, int ow, int ox, 
 		  int type, int dev, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 	char tmp[HOSTFS_BUFSIZE];
 	int err = -ENOMEM;
 	int mode = 0;
@@ -127,30 +127,32 @@ static int stat_file(const char *file, v
 		     unsigned long *ctime_out, int *blksize_out, 
 		     unsigned long long *blocks_out)
 {
-	const char *path[] = { jail_dir, file, NULL };
-
+	const char *path[] = { jail_dir, mount, file, NULL };
+	int uid;
+	*uid_out = 0; /* This should use a mount option */
 	return(host_stat_file(path, dev_out, inode_out, mode_out, nlink_out, 
-			      uid_out, gid_out, size_out, atime_out, mtime_out, 
+			      &uid, gid_out, size_out, atime_out, mtime_out, 
 			      ctime_out, blksize_out, blocks_out));
+
 }
 
 static int file_type(const char *file, int *rdev, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_file_type(path, rdev));
 }
 
 static int open_file(char *file, int uid, int gid, int r, int w, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_open_file(path, r, w));
 }
 
 static void *open_dir(char *file, int uid, int gid, int *err_out, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_open_dir(path, err_out));
 }
@@ -170,7 +172,7 @@ static int file_create(char *file, int u
 		       int gr, int gw, int gx, int or, int ow, int ox, 
 		       void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_file_create(path, ur, uw, ux, gr, gw, gx, or, ow, ox));
 }
@@ -178,7 +180,7 @@ static int file_create(char *file, int u
 static int set_attr(const char *file, struct hostfs_iattr *attrs, 
 		    void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_set_attr(path, attrs));
 }
@@ -186,28 +188,28 @@ static int set_attr(const char *file, st
 static int make_symlink(const char *from, const char *to, int uid, int gid,
 			void *mount)
 {
-	const char *path[] = { jail_dir, from, NULL };
+	const char *path[] = { jail_dir, mount, from, NULL };
 
 	return(host_make_symlink(path, to));
 }
 
 static int unlink_file(const char *file, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_unlink_file(path));
 }
 
 static int mk_dir(const char *file, int mode, int uid, int gid, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_mkdir(path, mode));
 }
 
 static int rm_dir(const char *file, int uid, int gid, void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_rmdir(path));
 }
@@ -215,8 +217,8 @@ static int rm_dir(const char *file, int 
 static int link_file(const char *to, const char *from, int uid, int gid, 
 		     void *mount)
 {
-	const char *to_path[] = { jail_dir, to, NULL };
-	const char *from_path[] = { jail_dir, from, NULL };
+	const char *to_path[] = { jail_dir, mount, to, NULL };
+	const char *from_path[] = { jail_dir, mount, from, NULL };
 
 	return(host_link_file(to_path, from_path));
 }
@@ -224,15 +226,15 @@ static int link_file(const char *to, con
 static int read_link(char *file, int uid, int gid, char *buf, int size, 
 		     void *mount)
 {
-	const char *path[] = { jail_dir, file, NULL };
+	const char *path[] = { jail_dir, mount, file, NULL };
 
 	return(host_readlink(path, buf, size));
 }
 
 static int rename_file(char *from, char *to, void *mount)
 {
-	const char *to_path[] = { jail_dir, to, NULL };
-	const char *from_path[] = { jail_dir, from, NULL };
+	const char *to_path[] = { jail_dir, mount, to, NULL };
+	const char *from_path[] = { jail_dir, mount, from, NULL };
 
 	return(host_rename_file(to_path, from_path));
 }
@@ -243,7 +245,7 @@ static int stat_fs(long *bsize_out, long
 		   void *fsid_out, int fsid_size, long *namelen_out, 
 		   long *spare_out, void *mount)
 {
-	const char *path[] = { jail_dir, mount, NULL };
+	const char *path[] = { jail_dir, mount, mount, NULL };
 
 	return(host_statfs(path, bsize_out, blocks_out, bfree_out, bavail_out, 
 			   files_out, ffree_out, fsid_out, fsid_size, 
@@ -279,8 +281,11 @@ static struct externfs_file_ops hostfs_f
 static struct externfs_file_ops *mount_fs(char *mount_arg, 
 					  void **mount_data_out)
 {
-	if(host_root_filename(mount_arg, mount_data_out))
+	char *root;
+	if(host_root_filename(mount_arg, &root))
 		return(NULL);
+
+	*mount_data_out = uml_strdup(root);
 
 	return(&hostfs_file_ops);
 }

Re: [uml-devel] [patch] 2.4 hostfs no longer mounts specified directory

[Jeff Dike]

Thanks, applied.

Except for this bit:

@@ -243,7 +245,7 @@ 
static int stat_fs(long *bsize_out, long
 		   void *fsid_out, int fsid_size, long *namelen_out, 
 		   long *spare_out, void *mount)
 {
-	const char *path[] = { jail_dir, mount, NULL };
+	const char *path[] = { jail_dir, mount, mount, NULL };
 
 	return(host_statfs(path, bsize_out, blocks_out, bfree_out, bavail_out, 
 			   files_out, ffree_out, fsid_out, fsid_size, 

What's up with that, anyway?

				Jeff



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Re: [uml-devel] [patch] 2.4 hostfs no longer mounts specified directory

[Henrik Nordstrom]

On Tue, 4 May 2004, Jeff Dike wrote:

> @@ -243,7 +245,7 @@ 
> static int stat_fs(long *bsize_out, long
>  		   void *fsid_out, int fsid_size, long *namelen_out, 
>  		   long *spare_out, void *mount)
>  {
> -	const char *path[] = { jail_dir, mount, NULL };
> +	const char *path[] = { jail_dir, mount, mount, NULL };
>  
>  	return(host_statfs(path, bsize_out, blocks_out, bfree_out, bavail_out, 
>  			   files_out, ffree_out, fsid_out, fsid_size, 
> 
> What's up with that, anyway?

Copy-paste error...

Regards
Henrik



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