[PATCH 3.10 35/44] nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races

Greg Kroah-Hartman
2015-01-14T07:39:20Z

From: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

commit 705304a863cc41585508c0f476f6d3ec28cf7e00 upstream.

Same story as in commit 41080b5a2401 ("nfsd race fixes: ext2") (similar
ext2 fix) except that nilfs2 needs to use insert_inode_locked4() instead
of insert_inode_locked() and a bug of a check for dead inodes needs to
be fixed.

If nilfs_iget() is called from nfsd after nilfs_new_inode() calls
insert_inode_locked4(), nilfs_iget() will wait for unlock_new_inode() at
the end of nilfs_mkdir()/nilfs_create()/etc to unlock the inode.

If nilfs_iget() is called before nilfs_new_inode() calls
insert_inode_locked4(), it will create an in-core inode and read its
data from the on-disk inode. But, nilfs_iget() will find i_nlink equals
zero and fail at nilfs_read_inode_common(), which will lead it to call
iget_failed() and cleanly fail.

However, this sanity check doesn't work as expected for reused on-disk
inodes because they leave a non-zero value in i_mode field and it
hinders the test of i_nlink. This patch also fixes the issue by
removing the test on i_mode that nilfs2 doesn't need.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nilfs2/inode.c | 32 ++++++++++++++++++++++++--------
fs/nilfs2/namei.c | 15 ++++++++++++---
2 files changed, 36 insertions(+), 11 deletions(-)

--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -49,6 +49,8 @@ struct nilfs_iget_args {
int for_gc;
};

+static int nilfs_iget_test(struct inode *inode, void *opaque);
+
void nilfs_inode_add_blocks(struct inode *inode, int n)
{
struct nilfs_root *root = NILFS_I(inode)->i_root;
@@ -347,6 +349,17 @@ const struct address_space_operations ni
.is_partially_uptodate = block_is_partially_uptodate,
};

+static int nilfs_insert_inode_locked(struct inode *inode,
+ struct nilfs_root *root,
+ unsigned long ino)
+{
+ struct nilfs_iget_args args = {
+ .ino = ino, .root = root, .cno = 0, .for_gc = 0
+ };
+
+ return insert_inode_locked4(inode, ino, nilfs_iget_test, &args);
+}
+
struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
{
struct super_block *sb = dir->i_sb;
@@ -382,7 +395,7 @@ struct inode *nilfs_new_inode(struct ino
if (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)) {
err = nilfs_bmap_read(ii->i_bmap, NULL);
if (err < 0)
- goto failed_bmap;
+ goto failed_after_creation;

set_bit(NILFS_I_BMAP, &ii->i_state);
/* No lock is needed; iget() ensures it. */
@@ -398,21 +411,24 @@ struct inode *nilfs_new_inode(struct ino
spin_lock(&nilfs->ns_next_gen_lock);
inode->i_generation = nilfs->ns_next_generation++;
spin_unlock(&nilfs->ns_next_gen_lock);
- insert_inode_hash(inode);
+ if (nilfs_insert_inode_locked(inode, root, ino) < 0) {
+ err = -EIO;
+ goto failed_after_creation;
+ }

err = nilfs_init_acl(inode, dir);
if (unlikely(err))
- goto failed_acl; /* never occur. When supporting
+ goto failed_after_creation; /* never occur. When supporting
nilfs_init_acl(), proper cancellation of
above jobs should be considered */

return inode;

- failed_acl:
- failed_bmap:
+ failed_after_creation:
clear_nlink(inode);
+ unlock_new_inode(inode);
iput(inode); /* raw_inode will be deleted through
- generic_delete_inode() */
+ nilfs_evict_inode() */
goto failed;

failed_ifile_create_inode:
@@ -460,8 +476,8 @@ int nilfs_read_inode_common(struct inode
inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
inode->i_ctime.tv_nsec = le32_to_cpu(raw_inode->i_ctime_nsec);
inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
- if (inode->i_nlink == 0 && inode->i_mode == 0)
- return -EINVAL; /* this inode is deleted */
+ if (inode->i_nlink == 0)
+ return -ESTALE; /* this inode is deleted */

inode->i_blocks = le64_to_cpu(raw_inode->i_blocks);
ii->i_flags = le32_to_cpu(raw_inode->i_flags);
--- a/fs/nilfs2/namei.c
+++ b/fs/nilfs2/namei.c
@@ -51,9 +51,11 @@ static inline int nilfs_add_nondir(struc
int err = nilfs_add_link(dentry, inode);
if (!err) {
d_instantiate(dentry, inode);
+ unlock_new_inode(inode);
return 0;
}
inode_dec_link_count(inode);
+ unlock_new_inode(inode);
iput(inode);
return err;
}
@@ -182,6 +184,7 @@ out:
out_fail:
drop_nlink(inode);
nilfs_mark_inode_dirty(inode);
+ unlock_new_inode(inode);
iput(inode);
goto out;
}
@@ -201,11 +204,15 @@ static int nilfs_link(struct dentry *old
inode_inc_link_count(inode);
ihold(inode);

- err = nilfs_add_nondir(dentry, inode);
- if (!err)
+ err = nilfs_add_link(dentry, inode);
+ if (!err) {
+ d_instantiate(dentry, inode);
err = nilfs_transaction_commit(dir->i_sb);
- else
+ } else {
+ inode_dec_link_count(inode);
+ iput(inode);
nilfs_transaction_abort(dir->i_sb);
+ }

return err;
}
@@ -243,6 +250,7 @@ static int nilfs_mkdir(struct inode *dir

nilfs_mark_inode_dirty(inode);
d_instantiate(dentry, inode);
+ unlock_new_inode(inode);
out:
if (!err)
err = nilfs_transaction_commit(dir->i_sb);
@@ -255,6 +263,7 @@ out_fail:
drop_nlink(inode);
drop_nlink(inode);
nilfs_mark_inode_dirty(inode);
+ unlock_new_inode(inode);
iput(inode);
out_dir:
drop_nlink(dir);