4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Al Viro viro@zeniv.linux.org.uk
[ 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@zeniv.linux.org.uk Stable-dep-of: 0d5a4f8f775f ("fs: Fix error checking for d_hash_and_lookup()") Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/cifs/cifsfs.c | 7 +------ fs/debugfs/inode.c | 6 +----- fs/kernfs/mount.c | 2 +- fs/namei.c | 20 ++++++++++++++++++++ fs/nfsd/nfs3xdr.c | 4 +--- fs/nfsd/nfs4xdr.c | 11 +---------- fs/overlayfs/namei.c | 24 ++++++++---------------- fs/quota/dquot.c | 8 +------- include/linux/namei.h | 1 + 9 files changed, 35 insertions(+), 48 deletions(-)
--- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -663,11 +663,6 @@ cifs_get_root(struct smb_vol *vol, struc 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, struc 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)); --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -275,13 +275,9 @@ struct dentry *debugfs_lookup(const char 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); --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -212,7 +212,7 @@ struct dentry *kernfs_node_dentry(struct 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)) --- a/fs/namei.c +++ b/fs/namei.c @@ -2575,6 +2575,26 @@ struct dentry *lookup_one_len_unlocked(c } 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) { --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -855,13 +855,11 @@ compose_entry_fh(struct nfsd3_readdirres } 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); --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -2984,18 +2984,9 @@ nfsd4_encode_dirent_fattr(struct xdr_str __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); /* --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -203,7 +203,7 @@ static int ovl_lookup_single(struct dent 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 dent 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 o 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 o 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 o 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 o }
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 *d 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 *d break; } } else { - if (this->d_inode) { - positive = !ovl_is_whiteout(this); - done = true; - } + positive = !ovl_is_whiteout(this); + done = true; dput(this); } } --- a/fs/quota/dquot.c +++ b/fs/quota/dquot.c @@ -2535,21 +2535,15 @@ int dquot_quota_on_mount(struct super_bl 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, DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);
-out: dput(dentry); return error; } --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -84,6 +84,7 @@ extern int kern_path_mountpoint(int, con 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 *);