udf: fix the udf_iget() vs. udf_new_inode() races

Currently udf_iget() (triggered by NFS) can race with udf_new_inode()
leading to two inode structures with the same inode number:

nfsd: iget_locked() creates inode
nfsd: try to read from disk, block on that.
udf_new_inode(): allocate inode with that inumber
udf_new_inode(): insert it into icache, set it up and dirty
udf_write_inode(): write inode into buffer cache
nfsd: get CPU again, look into buffer cache, see nice and sane on-disk
  inode, set the in-core inode from it

Fix the problem by putting inode into icache in locked state (I_NEW set)
and unlocking it only after it's fully set up.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jan Kara <jack@suse.cz>

2 files changed, 13 insertions, 1 deletions

diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
index 647370d70175..598f33bdcd26 100644
--- a/fs/udf/ialloc.c
+++ b/fs/udf/ialloc.c
@@ -124,7 +124,12 @@ struct inode *udf_new_inode(struct inode *dir, umode_t mode, int *err)
                 iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
         inode->i_mtime = inode->i_atime = inode->i_ctime =
                 iinfo->i_crtime = current_fs_time(inode->i_sb);
-        insert_inode_hash(inode);
+        if (unlikely(insert_inode_locked(inode) < 0)) {
+                make_bad_inode(inode);
+                iput(inode);
+                *err = -EIO;
+                return NULL;
+        }
         mark_inode_dirty(inode);
 
         *err = 0;
diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index abec86466735..d106fdd1bef7 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -559,6 +559,7 @@ static int udf_add_nondir(struct dentry *dentry, struct inode *inode)
         fi = udf_add_entry(dir, dentry, &fibh, &cfi, &err);
         if (unlikely(!fi)) {
                 inode_dec_link_count(inode);
+                unlock_new_inode(inode);
                 iput(inode);
                 return err;
         }
@@ -572,6 +573,7 @@ static int udf_add_nondir(struct dentry *dentry, struct inode *inode)
         if (fibh.sbh != fibh.ebh)
                 brelse(fibh.ebh);
         brelse(fibh.sbh);
+        unlock_new_inode(inode);
         d_instantiate(dentry, inode);
 
         return 0;
@@ -619,6 +621,7 @@ static int udf_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
         mark_inode_dirty(inode);
 
         d_tmpfile(dentry, inode);
+        unlock_new_inode(inode);
         return 0;
 }
 
@@ -660,6 +663,7 @@ static int udf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
         fi = udf_add_entry(inode, NULL, &fibh, &cfi, &err);
         if (!fi) {
                 inode_dec_link_count(inode);
+                unlock_new_inode(inode);
                 iput(inode);
                 goto out;
         }
@@ -678,6 +682,7 @@ static int udf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
         if (!fi) {
                 clear_nlink(inode);
                 mark_inode_dirty(inode);
+                unlock_new_inode(inode);
                 iput(inode);
                 goto out;
         }
@@ -689,6 +694,7 @@ static int udf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
         udf_write_fi(dir, &cfi, fi, &fibh, NULL, NULL);
         inc_nlink(dir);
         mark_inode_dirty(dir);
+        unlock_new_inode(inode);
         d_instantiate(dentry, inode);
         if (fibh.sbh != fibh.ebh)
                 brelse(fibh.ebh);
@@ -996,6 +1002,7 @@ out:
 out_no_entry:
         up_write(&iinfo->i_data_sem);
         inode_dec_link_count(inode);
+        unlock_new_inode(inode);
         iput(inode);
         goto out;
 }