[PATCH] knfsd: Make ext3 reject filehandles referring to invalid inode number

Inodes earlier than the 'first' inode (e.g.  journal, resize) should be
rejected early - except the root inode.  Also inode numbers that are too
big should be rejected early.

[akpm@osdl.org: cleanup]
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 813d589cc6c0..3559086eee5f 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -554,6 +554,47 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs)
         return 0;
 }
 
+
+static struct dentry *ext3_get_dentry(struct super_block *sb, void *vobjp)
+{
+        __u32 *objp = vobjp;
+        unsigned long ino = objp[0];
+        __u32 generation = objp[1];
+        struct inode *inode;
+        struct dentry *result;
+
+        if (ino < EXT3_FIRST_INO(sb) && ino != EXT3_ROOT_INO)
+                return ERR_PTR(-ESTALE);
+        if (ino > le32_to_cpu(EXT3_SB(sb)->s_es->s_inodes_count))
+                return ERR_PTR(-ESTALE);
+
+        /* iget isn't really right if the inode is currently unallocated!!
+         *
+         * ext3_read_inode will return a bad_inode if the inode had been
+         * deleted, so we should be safe.
+         *
+         * Currently we don't know the generation for parent directory, so
+         * a generation of 0 means "accept any"
+         */
+        inode = iget(sb, ino);
+        if (inode == NULL)
+                return ERR_PTR(-ENOMEM);
+        if (is_bad_inode(inode) ||
+            (generation && inode->i_generation != generation)) {
+                iput(inode);
+                return ERR_PTR(-ESTALE);
+        }
+        /* now to find a dentry.
+         * If possible, get a well-connected one
+         */
+        result = d_alloc_anon(inode);
+        if (!result) {
+                iput(inode);
+                return ERR_PTR(-ENOMEM);
+        }
+        return result;
+}
+
 #ifdef CONFIG_QUOTA
 #define QTYPE2NAME(t) ((t)==USRQUOTA?"user":"group")
 #define QTYPE2MOPT(on, t) ((t)==USRQUOTA?((on)##USRJQUOTA):((on)##GRPJQUOTA))
@@ -622,6 +663,7 @@ static struct super_operations ext3_sops = {
 
 static struct export_operations ext3_export_ops = {
         .get_parent = ext3_get_parent,
+        .get_dentry = ext3_get_dentry,
 };
 
 enum {