[PATCH] ext3: avoid triggering ext3_error on bad NFS file handle

The inode number out of an NFS file handle gets passed eventually to
ext3_get_inode_block() without any checking.  If ext3_get_inode_block()
allows it to trigger an error, then bad filehandles can have unpleasant
effect - ext3_error() will usually cause a forced read-only remount, or a
panic if `errors=panic' was used.

So remove the call to ext3_error there and put a matching check in
ext3/namei.c where inode numbers are read off storage.

[akpm@osdl.org: fix off-by-one error]
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: <stable@kernel.org>
Cc: "Stephen C. Tweedie" <sct@redhat.com>
Cc: Eric Sandeen <esandeen@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/ext3/inode.c

@@ -2402,14 +2402,15 @@ static ext3_fsblk_t ext3_get_inode_block(struct super_block *sb,
 	struct buffer_head *bh;
 	struct ext3_group_desc * gdp;
 
-
-	if ((ino != EXT3_ROOT_INO && ino != EXT3_JOURNAL_INO &&
-		ino != EXT3_RESIZE_INO && ino < EXT3_FIRST_INO(sb)) ||
-		ino > le32_to_cpu(EXT3_SB(sb)->s_es->s_inodes_count)) {
-		ext3_error(sb, "ext3_get_inode_block",
-			    "bad inode number: %lu", ino);
+	if (!ext3_valid_inum(sb, ino)) {
+		/*
+		 * This error is already checked for in namei.c unless we are
+		 * looking at an NFS filehandle, in which case no error
+		 * report is needed
+		 */
 		return 0;
 	}
+
 	block_group = (ino - 1) / EXT3_INODES_PER_GROUP(sb);
 	if (block_group >= EXT3_SB(sb)->s_groups_count) {
 		ext3_error(sb,"ext3_get_inode_block","group >= groups count");

fs/ext3/namei.c

@@ -1000,7 +1000,12 @@ static struct dentry *ext3_lookup(struct inode * dir, struct dentry *dentry, str
 	if (bh) {
 		unsigned long ino = le32_to_cpu(de->inode);
 		brelse (bh);
-		inode = iget(dir->i_sb, ino);
+		if (!ext3_valid_inum(dir->i_sb, ino)) {
+			ext3_error(dir->i_sb, "ext3_lookup",
+				   "bad inode number: %lu", ino);
+			inode = NULL;
+		} else
+			inode = iget(dir->i_sb, ino);
 
 		if (!inode)
 			return ERR_PTR(-EACCES);
@@ -1028,7 +1033,13 @@ struct dentry *ext3_get_parent(struct dentry *child)
 		return ERR_PTR(-ENOENT);
 	ino = le32_to_cpu(de->inode);
 	brelse(bh);
-	inode = iget(child->d_inode->i_sb, ino);
+
+	if (!ext3_valid_inum(child->d_inode->i_sb, ino)) {
+		ext3_error(child->d_inode->i_sb, "ext3_get_parent",
+			   "bad inode number: %lu", ino);
+		inode = NULL;
+	} else
+		inode = iget(child->d_inode->i_sb, ino);
 
 	if (!inode)
 		return ERR_PTR(-EACCES);

include/linux/ext3_fs.h

@@ -492,6 +492,15 @@ static inline struct ext3_inode_info *EXT3_I(struct inode *inode)
 {
 	return container_of(inode, struct ext3_inode_info, vfs_inode);
 }
+
+static inline int ext3_valid_inum(struct super_block *sb, unsigned long ino)
+{
+	return ino == EXT3_ROOT_INO ||
+		ino == EXT3_JOURNAL_INO ||
+		ino == EXT3_RESIZE_INO ||
+		(ino >= EXT3_FIRST_INO(sb) &&
+		 ino <= le32_to_cpu(EXT3_SB(sb)->s_es->s_inodes_count));
+}
 #else
 /* Assume that user mode programs are passing in an ext3fs superblock, not
  * a kernel struct super_block.  This will allow us to call the feature-test