From: Amir Goldstein <amir73il@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Vivek Goyal <vgoyal@redhat.com>,
linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH v3 4/4] ovl: make ovl_create_real() cope with vfs_mkdir() safely
Date: Tue, 15 May 2018 13:26:12 +0300 [thread overview]
Message-ID: <1526379972-20923-5-git-send-email-amir73il@gmail.com> (raw)
In-Reply-To: <1526379972-20923-1-git-send-email-amir73il@gmail.com>
From: Al Viro <viro@zeniv.linux.org.uk>
vfs_mkdir() may succeed and leave the dentry passed to it unhashed and
negative. ovl_create_real() is the last caller breaking when that
happens.
Pass newdentry to ovl_create_real() by ref, so in the case above, if
lookup finds a good dentry, newdentry will be replaced by the positive
hashed one.
[amir: split re-factoring to prep patch
pass dentry by ref
factor out helper ovl_create_real_dir()
add pr_warn() if mkdir succeeds and lookup fails]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/dir.c | 42 +++++++++++++++++++++++++++++++++++++-----
fs/overlayfs/overlayfs.h | 2 +-
fs/overlayfs/super.c | 2 +-
3 files changed, 39 insertions(+), 7 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 45f5f9232e71..a90328c41307 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -114,9 +114,41 @@ int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
goto out;
}
-int ovl_create_real(struct inode *dir, struct dentry *newdentry,
+static int ovl_create_real_dir(struct inode *dir, struct dentry **pnewdentry,
+ umode_t mode)
+{
+ struct dentry *newdentry = *pnewdentry;
+ int err;
+
+ err = ovl_do_mkdir(dir, newdentry, mode, true);
+ /*
+ * vfs_mkdir() may succeed and leave the dentry passed
+ * to it unhashed and negative. If that happens, try to
+ * lookup a new hashed and positive dentry.
+ */
+ if (!err && unlikely(d_unhashed(newdentry))) {
+ struct dentry *d;
+
+ d = lookup_one_len(newdentry->d_name.name,
+ newdentry->d_parent,
+ newdentry->d_name.len);
+ if (IS_ERR(d)) {
+ err = PTR_ERR(d);
+ pr_warn("overlayfs: failed lookup after mkdir (%pd2, err=%i).\n",
+ newdentry, err);
+ return err;
+ }
+ dput(newdentry);
+ *pnewdentry = d;
+ }
+
+ return err;
+}
+
+int ovl_create_real(struct inode *dir, struct dentry **pnewdentry,
struct cattr *attr, struct dentry *hardlink, bool debug)
{
+ struct dentry *newdentry = *pnewdentry;
int err;
if (newdentry->d_inode)
@@ -131,7 +163,7 @@ int ovl_create_real(struct inode *dir, struct dentry *newdentry,
break;
case S_IFDIR:
- err = ovl_do_mkdir(dir, newdentry, attr->mode, debug);
+ err = ovl_create_real_dir(dir, pnewdentry, attr->mode);
break;
case S_IFCHR:
@@ -150,7 +182,7 @@ int ovl_create_real(struct inode *dir, struct dentry *newdentry,
err = -EPERM;
}
}
- if (!err && WARN_ON(!newdentry->d_inode)) {
+ if (!err && WARN_ON(!d_inode(*pnewdentry))) {
/*
* Not quite sure if non-instantiated dentry is legal or not.
* VFS doesn't seem to care so check and warn here.
@@ -171,7 +203,7 @@ struct dentry *ovl_create_temp(struct dentry *workdir, struct cattr *attr,
if (IS_ERR(temp))
return temp;
- err = ovl_create_real(wdir, temp, attr, hardlink, true);
+ err = ovl_create_real(wdir, &temp, attr, hardlink, true);
if (err) {
dput(temp);
return ERR_PTR(err);
@@ -261,7 +293,7 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
err = PTR_ERR(newdentry);
if (IS_ERR(newdentry))
goto out_unlock;
- err = ovl_create_real(udir, newdentry, attr, hardlink, false);
+ err = ovl_create_real(udir, &newdentry, attr, hardlink, false);
if (err)
goto out_dput;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 967183175ef5..a84599268d10 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -378,7 +378,7 @@ struct cattr {
umode_t mode;
const char *link;
};
-int ovl_create_real(struct inode *dir, struct dentry *newdentry,
+int ovl_create_real(struct inode *dir, struct dentry **pnewdentry,
struct cattr *attr,
struct dentry *hardlink, bool debug);
struct dentry *ovl_create_temp(struct dentry *workdir, struct cattr *attr,
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 492d534058ae..d83c0543c03c 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -603,7 +603,7 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
goto retry;
}
- err = ovl_create_real(dir, work,
+ err = ovl_create_real(dir, &work,
&(struct cattr){.mode = S_IFDIR | 0},
NULL, true);
if (err)
--
2.7.4
prev parent reply other threads:[~2018-05-15 10:25 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-15 10:26 [PATCH v3 0/4] Overlayfs mkdir related fixes Amir Goldstein
2018-05-15 10:26 ` [PATCH v3 1/4] ovl: use insert_inode_locked4() to hash a newly created inode Amir Goldstein
2018-05-15 13:23 ` Vivek Goyal
2018-05-15 13:37 ` Amir Goldstein
2018-05-16 8:34 ` Miklos Szeredi
2018-05-16 9:51 ` Amir Goldstein
2018-05-16 10:14 ` Miklos Szeredi
2018-05-16 11:03 ` Amir Goldstein
2018-05-17 6:03 ` Amir Goldstein
2018-05-17 8:10 ` Miklos Szeredi
2018-05-17 8:45 ` Amir Goldstein
2018-05-17 8:53 ` Miklos Szeredi
2018-05-17 8:58 ` Amir Goldstein
2018-05-17 9:07 ` Miklos Szeredi
2018-05-17 16:14 ` Amir Goldstein
2018-05-15 10:26 ` [PATCH v3 2/4] ovl: relax WARN_ON() real inode attributes mismatch Amir Goldstein
2018-05-15 12:48 ` Vivek Goyal
2018-05-15 12:55 ` Amir Goldstein
2018-05-16 10:29 ` Miklos Szeredi
2018-05-16 11:06 ` Amir Goldstein
2018-05-16 11:18 ` Miklos Szeredi
2018-05-16 13:46 ` Amir Goldstein
2018-05-15 10:26 ` [PATCH v3 3/4] ovl: create helper ovl_create_temp() Amir Goldstein
2018-05-16 10:41 ` Miklos Szeredi
2018-05-16 11:15 ` Amir Goldstein
2018-05-16 11:37 ` Miklos Szeredi
2018-05-15 10:26 ` Amir Goldstein [this message]
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