[PATCH 3.16 289/366] udf: fix the udf_iget() vs. udf_new_inode() races

Ben Hutchings
2018-10-14T15:25:41Z

From: Al Viro <viro@zeniv.linux.org.uk>

commit b231509616feb911c2a7a8814d58c0014ef5b17f upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/udf/ialloc.c | 7 ++++++-
fs/udf/namei.c | 7 +++++++
2 files changed, 13 insertions(+), 1 deletion(-)

--- a/fs/udf/ialloc.c
+++ b/fs/udf/ialloc.c
@@ -123,7 +123,12 @@ struct inode *udf_new_inode(struct inode
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;
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -562,6 +562,7 @@ static int udf_add_nondir(struct dentry
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;
}
@@ -575,6 +576,7 @@ static int udf_add_nondir(struct dentry
if (fibh.sbh != fibh.ebh)
brelse(fibh.ebh);
brelse(fibh.sbh);
+ unlock_new_inode(inode);
d_instantiate(dentry, inode);

return 0;
@@ -622,6 +624,7 @@ static int udf_tmpfile(struct inode *dir
mark_inode_dirty(inode);

d_tmpfile(dentry, inode);
+ unlock_new_inode(inode);
return 0;
}

@@ -663,6 +666,7 @@ static int udf_mkdir(struct inode *dir,
fi = udf_add_entry(inode, NULL, &fibh, &cfi, &err);
if (!fi) {
inode_dec_link_count(inode);
+ unlock_new_inode(inode);
iput(inode);
goto out;
}
@@ -681,6 +685,7 @@ static int udf_mkdir(struct inode *dir,
if (!fi) {
clear_nlink(inode);
mark_inode_dirty(inode);
+ unlock_new_inode(inode);
iput(inode);
goto out;
}
@@ -692,6 +697,7 @@ static int udf_mkdir(struct inode *dir,
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);
@@ -999,6 +1005,7 @@ out:
out_no_entry:
up_write(&iinfo->i_data_sem);
inode_dec_link_count(inode);
+ unlock_new_inode(inode);
iput(inode);
goto out;
}