[PATCH] knfsd: Have ext2 reject file handles with bad inode numbers early

This prevents bad inode numbers from triggering errors in ext2_get_inode.

[akpm@osdl.org: speedup, 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, 39 insertions, 0 deletions

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 681dea8f9532..ca5bfb6914d2 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -251,6 +251,44 @@ static struct super_operations ext2_sops = {
 #endif
 };
 
+static struct dentry *ext2_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 < EXT2_FIRST_INO(sb) && ino != EXT2_ROOT_INO)
+                return ERR_PTR(-ESTALE);
+        if (ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count))
+                return ERR_PTR(-ESTALE);
+
+        /* iget isn't really right if the inode is currently unallocated!!
+         * ext2_read_inode currently does appropriate checks, but
+         * it might be "neater" to call ext2_get_inode first and check
+         * if the inode is valid.....
+         */
+        inode = iget(sb, ino);
+        if (inode == NULL)
+                return ERR_PTR(-ENOMEM);
+        if (is_bad_inode(inode) ||
+            (generation && inode->i_generation != generation)) {
+                /* we didn't find the right inode.. */
+                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;
+}
+
 /* Yes, most of these are left as NULL!!
  * A NULL value implies the default, which works with ext2-like file
  * systems, but can be improved upon.
@@ -258,6 +296,7 @@ static struct super_operations ext2_sops = {
  */
 static struct export_operations ext2_export_ops = {
         .get_parent = ext2_get_parent,
+        .get_dentry = ext2_get_dentry,
 };
 
 static unsigned long get_sb_block(void **data)