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exportfs_decode_fh(): negative pinned may become positive without the parent locked

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[ Upstream commit a2ece088882666e1dc7113744ac912eb161e3f87 ]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Al Viro 2019-11-08 22:08:29 -05:00 committed by Greg Kroah-Hartman
parent dadd71d18a
commit af17e1fc7c
1 changed files with 19 additions and 12 deletions
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31
fs/exportfs/expfs.c
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@ -517,26 +517,33 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
* inode is actually connected to the parent.
*/
err = exportfs_get_name(mnt, target_dir, nbuf, result);
if (!err) {
inode_lock(target_dir->d_inode);
nresult = lookup_one_len(nbuf, target_dir,
strlen(nbuf));
inode_unlock(target_dir->d_inode);
if (!IS_ERR(nresult)) {
if (nresult->d_inode) {
dput(result);
result = nresult;
} else
dput(nresult);
}
if (err) {
dput(target_dir);
goto err_result;
}
inode_lock(target_dir->d_inode);
nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
if (!IS_ERR(nresult)) {
if (unlikely(nresult->d_inode != result->d_inode)) {
dput(nresult);
nresult = ERR_PTR(-ESTALE);
}
}
inode_unlock(target_dir->d_inode);
/*
* At this point we are done with the parent, but it's pinned
* by the child dentry anyway.
*/
dput(target_dir);
if (IS_ERR(nresult)) {
err = PTR_ERR(nresult);
goto err_result;
}
dput(result);
result = nresult;
/*
* And finally make sure the dentry is actually acceptable
* to NFSD.