[PATCH] udf: initialize parts of inode earlier in create

I saw an oops down this path when trying to create a new file on a UDF
filesystem which was internally marked as readonly, but mounted rw:

udf_create
        udf_new_inode
                new_inode
                        alloc_inode
                        	udf_alloc_inode
                udf_new_block
                        returns EIO due to readonlyness
                iput (on error)
                        udf_put_inode
                                udf_discard_prealloc
                                        udf_next_aext
                                                udf_current_aext
                                                        udf_get_fileshortad
                                                                OOPS

the udf_discard_prealloc() path was examining uninitialized fields of the
udf inode.

udf_discard_prealloc() already has this code to short-circuit the discard
path if no extents are preallocated:

        if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_IN_ICB ||
                inode->i_size == UDF_I_LENEXTENTS(inode))
        {
                return;
        }

so if we initialize UDF_I_LENEXTENTS(inode) = 0 earlier in udf_new_inode,
we won't try to free the (not) preallocated blocks, since this will match
the i_size = 0 set when the inode was initialized.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/udf/ialloc.c

@@ -75,6 +75,12 @@ struct inode * udf_new_inode (struct inode *dir, int mode, int * err)
 	}
 	*err = -ENOSPC;
 
+	UDF_I_UNIQUE(inode) = 0;
+	UDF_I_LENEXTENTS(inode) = 0;
+	UDF_I_NEXT_ALLOC_BLOCK(inode) = 0;
+	UDF_I_NEXT_ALLOC_GOAL(inode) = 0;
+	UDF_I_STRAT4096(inode) = 0;
+
 	block = udf_new_block(dir->i_sb, NULL, UDF_I_LOCATION(dir).partitionReferenceNum,
 		start, err);
 	if (*err)
@@ -84,11 +90,6 @@ struct inode * udf_new_inode (struct inode *dir, int mode, int * err)
 	}
 
 	mutex_lock(&sbi->s_alloc_mutex);
-	UDF_I_UNIQUE(inode) = 0;
-	UDF_I_LENEXTENTS(inode) = 0;
-	UDF_I_NEXT_ALLOC_BLOCK(inode) = 0;
-	UDF_I_NEXT_ALLOC_GOAL(inode) = 0;
-	UDF_I_STRAT4096(inode) = 0;
 	if (UDF_SB_LVIDBH(sb))
 	{
 		struct logicalVolHeaderDesc *lvhd;