[PATCH] sysfs: backport of sysfs_readdir fix from 2.6.22.y to 2.6.16.y (CVE-2007-3104)

[Miloslav Semler <majkls@prepere.com>]

This patch solves CVE-2007-3104  - sysfs_readdir oops.
More can be found here: 
http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.22.y.git;a=commit;h=dc351252b33f8fede396d6173dba117bcb933607

Signed-off-by: Miloslav Semler
---
diff -uprN linux-2.6.16.53/fs/sysfs/dir.c linux-2.6.16.53-new/fs/sysfs/dir.c
--- linux-2.6.16.53/fs/sysfs/dir.c      2007-07-25 23:05:45.000000000 +0200
+++ linux-2.6.16.53-new/fs/sysfs/dir.c  2007-09-23 18:18:09.000000000 +0200
@@ -29,6 +29,14 @@ static struct dentry_operations sysfs_de
        .d_iput         = sysfs_d_iput,
 };

+static unsigned int sysfs_inode_counter;
+ino_t sysfs_get_inum(void)
+{
+       if (unlikely(sysfs_inode_counter < 3))
+               sysfs_inode_counter = 3;
+       return sysfs_inode_counter++;
+}
+
 /*
  * Allocates a new sysfs_dirent and links it to the parent sysfs_dirent
  */
@@ -40,8 +48,10 @@ static struct sysfs_dirent * sysfs_new_d
        sd = kmem_cache_alloc(sysfs_dir_cachep, GFP_KERNEL);
        if (!sd)
                return NULL;
+

        memset(sd, 0, sizeof(*sd));
+       sd->s_ino = sysfs_get_inum();
        atomic_set(&sd->s_count, 1);
        INIT_LIST_HEAD(&sd->s_children);
        list_add(&sd->s_sibling, &parent_sd->s_children);
@@ -385,7 +395,7 @@ static int sysfs_readdir(struct file * f

        switch (i) {
                case 0:
-                       ino = dentry->d_inode->i_ino;
+                        ino = parent_sd->s_ino;
                        if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
                                break;
                        filp->f_pos++;
@@ -415,10 +425,7 @@ static int sysfs_readdir(struct file * f

                                name = sysfs_get_name(next);
                                len = strlen(name);
-                               if (next->s_dentry)
-                                       ino = 
next->s_dentry->d_inode->i_ino;
-                               else
-                                       ino = iunique(sysfs_sb, 2);
+                                ino = next->s_ino;

                                if (filldir(dirent, name, len, 
filp->f_pos, ino,
                                                 dt_type(next)) < 0)
diff -uprN linux-2.6.16.53/fs/sysfs/inode.c 
linux-2.6.16.53-new/fs/sysfs/inode.c
--- linux-2.6.16.53/fs/sysfs/inode.c    2007-07-25 23:05:45.000000000 +0200
+++ linux-2.6.16.53-new/fs/sysfs/inode.c        2007-09-23 
18:18:09.000000000 +0200
@@ -119,6 +119,7 @@ struct inode * sysfs_new_inode(mode_t mo
                inode->i_mapping->a_ops = &sysfs_aops;
                inode->i_mapping->backing_dev_info = 
&sysfs_backing_dev_info;
                inode->i_op = &sysfs_inode_operations;
+                inode->i_ino = sd->s_ino;

                if (sd->s_iattr) {
                        /* sysfs_dirent has non-default attributes
diff -uprN linux-2.6.16.53/fs/sysfs/mount.c 
linux-2.6.16.53-new/fs/sysfs/mount.c
--- linux-2.6.16.53/fs/sysfs/mount.c    2007-07-25 23:05:45.000000000 +0200
+++ linux-2.6.16.53-new/fs/sysfs/mount.c        2007-09-23 
18:18:09.000000000 +0200
@@ -29,6 +29,7 @@ static struct sysfs_dirent sysfs_root =
        .s_element      = NULL,
        .s_type         = SYSFS_ROOT,
        .s_iattr        = NULL,
+        .s_ino          = 1,
 };

 static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
diff -uprN linux-2.6.16.53/include/linux/sysfs.h 
linux-2.6.16.53-new/include/linux/sysfs.h
--- linux-2.6.16.53/include/linux/sysfs.h       2007-07-25 
23:05:45.000000000 +0200
+++ linux-2.6.16.53-new/include/linux/sysfs.h   2007-09-23 
18:18:09.000000000 +0200
@@ -72,6 +72,7 @@ struct sysfs_dirent {
        void                    * s_element;
        int                     s_type;
        umode_t                 s_mode;
+        ino_t                   s_ino;
        struct dentry           * s_dentry;
        struct iattr            * s_iattr;
 };