This is a note to let you know that I've just added the patch titled
new helper: lookup_positive_unlocked()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
new-helper-lookup_positive_unlocked.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 89bac0624177b98d2140ffc0921df3bce1c11fe4
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Thu Oct 31 01:21:58 2019 -0400
new helper: lookup_positive_unlocked()
[ Upstream commit 6c2d4798a8d16cf4f3a28c3cd4af4f1dcbbb4d04 ]
Most of the callers of lookup_one_len_unlocked() treat negatives are
ERR_PTR(-ENOENT). Provide a helper that would do just that. Note
that a pinned positive dentry remains positive - it's ->d_inode is
stable, etc.; a pinned _negative_ dentry can become positive at any
point as long as you are not holding its parent at least shared.
So using lookup_one_len_unlocked() needs to be careful;
lookup_positive_unlocked() is safer and that's what the callers
end up open-coding anyway.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Stable-dep-of: 0d5a4f8f775f ("fs: Fix error checking for d_hash_and_lookup()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 52b1524b40cdc..ef1a43f4bd663 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -663,11 +663,6 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
struct inode *dir = d_inode(dentry);
struct dentry *child;
- if (!dir) {
- dput(dentry);
- dentry = ERR_PTR(-ENOENT);
- break;
- }
if (!S_ISDIR(dir->i_mode)) {
dput(dentry);
dentry = ERR_PTR(-ENOTDIR);
@@ -684,7 +679,7 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
while (*s && *s != sep)
s++;
- child = lookup_one_len_unlocked(p, dentry, s - p);
+ child = lookup_positive_unlocked(p, dentry, s - p);
dput(dentry);
dentry = child;
} while (!IS_ERR(dentry));
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 4661ecaf6741c..1e4ae78f64a8f 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -275,13 +275,9 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
if (!parent)
parent = debugfs_mount->mnt_root;
- dentry = lookup_one_len_unlocked(name, parent, strlen(name));
+ dentry = lookup_positive_unlocked(name, parent, strlen(name));
if (IS_ERR(dentry))
return NULL;
- if (!d_really_is_positive(dentry)) {
- dput(dentry);
- return NULL;
- }
return dentry;
}
EXPORT_SYMBOL_GPL(debugfs_lookup);
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 0b22c39dad477..b2a126a947e31 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -212,7 +212,7 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
dput(dentry);
return ERR_PTR(-EINVAL);
}
- dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
+ dtmp = lookup_positive_unlocked(kntmp->name, dentry,
strlen(kntmp->name));
dput(dentry);
if (IS_ERR(dtmp))
diff --git a/fs/namei.c b/fs/namei.c
index 9e8fca598acc5..0dbe38afef29b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2575,6 +2575,26 @@ struct dentry *lookup_one_len_unlocked(const char *name,
}
EXPORT_SYMBOL(lookup_one_len_unlocked);
+/*
+ * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT)
+ * on negatives. Returns known positive or ERR_PTR(); that's what
+ * most of the users want. Note that pinned negative with unlocked parent
+ * _can_ become positive at any time, so callers of lookup_one_len_unlocked()
+ * need to be very careful; pinned positives have ->d_inode stable, so
+ * this one avoids such problems.
+ */
+struct dentry *lookup_positive_unlocked(const char *name,
+ struct dentry *base, int len)
+{
+ struct dentry *ret = lookup_one_len_unlocked(name, base, len);
+ if (!IS_ERR(ret) && d_is_negative(ret)) {
+ dput(ret);
+ ret = ERR_PTR(-ENOENT);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(lookup_positive_unlocked);
+
#ifdef CONFIG_UNIX98_PTYS
int path_pts(struct path *path)
{
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index b90bea1c434eb..9f537decdd9c7 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -855,13 +855,11 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp,
} else
dchild = dget(dparent);
} else
- dchild = lookup_one_len_unlocked(name, dparent, namlen);
+ dchild = lookup_positive_unlocked(name, dparent, namlen);
if (IS_ERR(dchild))
return rv;
if (d_mountpoint(dchild))
goto out;
- if (d_really_is_negative(dchild))
- goto out;
if (dchild->d_inode->i_ino != ino)
goto out;
rv = fh_compose(fhp, exp, dchild, &cd->fh);
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 74ab20c89e752..bceb99a8a814a 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2984,18 +2984,9 @@ nfsd4_encode_dirent_fattr(struct xdr_stream *xdr, struct nfsd4_readdir *cd,
__be32 nfserr;
int ignore_crossmnt = 0;
- dentry = lookup_one_len_unlocked(name, cd->rd_fhp->fh_dentry, namlen);
+ dentry = lookup_positive_unlocked(name, cd->rd_fhp->fh_dentry, namlen);
if (IS_ERR(dentry))
return nfserrno(PTR_ERR(dentry));
- if (d_really_is_negative(dentry)) {
- /*
- * we're not holding the i_mutex here, so there's
- * a window where this directory entry could have gone
- * away.
- */
- dput(dentry);
- return nfserr_noent;
- }
exp_get(exp);
/*
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index badf039267a2f..e51dc7f16596c 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -203,7 +203,7 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
int err;
bool last_element = !post[0];
- this = lookup_one_len_unlocked(name, base, namelen);
+ this = lookup_positive_unlocked(name, base, namelen);
if (IS_ERR(this)) {
err = PTR_ERR(this);
this = NULL;
@@ -211,8 +211,6 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
goto out;
goto out_err;
}
- if (!this->d_inode)
- goto put_and_out;
if (ovl_dentry_weird(this)) {
/* Don't support traversing automounts and other weirdness */
@@ -654,7 +652,7 @@ struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
if (err)
return ERR_PTR(err);
- index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
+ index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len);
kfree(name.name);
if (IS_ERR(index)) {
if (PTR_ERR(index) == -ENOENT)
@@ -662,9 +660,7 @@ struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
return index;
}
- if (d_is_negative(index))
- err = 0;
- else if (ovl_is_whiteout(index))
+ if (ovl_is_whiteout(index))
err = -ESTALE;
else if (ovl_dentry_weird(index))
err = -EIO;
@@ -688,7 +684,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
if (err)
return ERR_PTR(err);
- index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
+ index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len);
if (IS_ERR(index)) {
err = PTR_ERR(index);
if (err == -ENOENT) {
@@ -703,9 +699,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
}
inode = d_inode(index);
- if (d_is_negative(index)) {
- goto out_dput;
- } else if (ovl_is_whiteout(index) && !verify) {
+ if (ovl_is_whiteout(index) && !verify) {
/*
* When index lookup is called with !verify for decoding an
* overlay file handle, a whiteout index implies that decode
@@ -1134,7 +1128,7 @@ bool ovl_lower_positive(struct dentry *dentry)
struct dentry *this;
struct dentry *lowerdir = poe->lowerstack[i].dentry;
- this = lookup_one_len_unlocked(name->name, lowerdir,
+ this = lookup_positive_unlocked(name->name, lowerdir,
name->len);
if (IS_ERR(this)) {
switch (PTR_ERR(this)) {
@@ -1151,10 +1145,8 @@ bool ovl_lower_positive(struct dentry *dentry)
break;
}
} else {
- if (this->d_inode) {
- positive = !ovl_is_whiteout(this);
- done = true;
- }
+ positive = !ovl_is_whiteout(this);
+ done = true;
dput(this);
}
}
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 303987d29b9c9..d901119e25b51 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2535,15 +2535,10 @@ int dquot_quota_on_mount(struct super_block *sb, char *qf_name,
struct dentry *dentry;
int error;
- dentry = lookup_one_len_unlocked(qf_name, sb->s_root, strlen(qf_name));
+ dentry = lookup_positive_unlocked(qf_name, sb->s_root, strlen(qf_name));
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- if (d_really_is_negative(dentry)) {
- error = -ENOENT;
- goto out;
- }
-
error = security_quota_on(dentry);
if (!error)
error = vfs_load_quota_inode(d_inode(dentry), type, format_id,
diff --git a/include/linux/namei.h b/include/linux/namei.h
index a78606e8e3df7..4632f4ca33426 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -84,6 +84,7 @@ extern int kern_path_mountpoint(int, const char *, struct path *, unsigned int);
extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
+extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
extern int follow_down_one(struct path *);
extern int follow_down(struct path *);
