ovl: lookup: do getxattr with mounter's permission

The getxattr() in ovl_is_opaquedir() was missed when converting all
operations on underlying fs to be done under mounter's permission.

This patch fixes this by moving the ovl_override_creds()/revert_creds() out
from ovl_lookup_real() to ovl_lookup().

Also convert to using vfs_getxattr() instead of directly calling
i_op->getxattr().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e2a94a2..8ccebaf 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -273,12 +273,11 @@ static bool ovl_is_opaquedir(struct dentry *dentry)
 {
        int res;
        char val;
-       struct inode *inode = dentry->d_inode;
 
-       if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
+       if (!d_is_dir(dentry))
                return false;
 
-       res = inode->i_op->getxattr(dentry, inode, OVL_XATTR_OPAQUE, &val, 1);
+       res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
        if (res == 1 && val == 'y')
                return true;
 
@@ -419,16 +418,12 @@ static bool ovl_dentry_weird(struct dentry *dentry)
                                  DCACHE_OP_COMPARE);
 }
 
-static inline struct dentry *ovl_lookup_real(struct super_block *ovl_sb,
-                                            struct dentry *dir,
+static inline struct dentry *ovl_lookup_real(struct dentry *dir,
                                             const struct qstr *name)
 {
-       const struct cred *old_cred;
        struct dentry *dentry;
 
-       old_cred = ovl_override_creds(ovl_sb);
        dentry = lookup_one_len_unlocked(name->name, dir, name->len);
-       revert_creds(old_cred);
 
        if (IS_ERR(dentry)) {
                if (PTR_ERR(dentry) == -ENOENT)
@@ -469,6 +464,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                          unsigned int flags)
 {
        struct ovl_entry *oe;
+       const struct cred *old_cred;
        struct ovl_entry *poe = dentry->d_parent->d_fsdata;
        struct path *stack = NULL;
        struct dentry *upperdir, *upperdentry = NULL;
@@ -479,9 +475,10 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
        unsigned int i;
        int err;
 
+       old_cred = ovl_override_creds(dentry->d_sb);
        upperdir = ovl_upperdentry_dereference(poe);
        if (upperdir) {
-               this = ovl_lookup_real(dentry->d_sb, upperdir, &dentry->d_name);
+               this = ovl_lookup_real(upperdir, &dentry->d_name);
                err = PTR_ERR(this);
                if (IS_ERR(this))
                        goto out;
@@ -514,8 +511,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                bool opaque = false;
                struct path lowerpath = poe->lowerstack[i];
 
-               this = ovl_lookup_real(dentry->d_sb,
-                                      lowerpath.dentry, &dentry->d_name);
+               this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
                err = PTR_ERR(this);
                if (IS_ERR(this)) {
                        /*
@@ -588,6 +584,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                ovl_copyattr(realdentry->d_inode, inode);
        }
 
+       revert_creds(old_cred);
        oe->opaque = upperopaque;
        oe->__upperdentry = upperdentry;
        memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
@@ -606,6 +603,7 @@ out_put:
 out_put_upper:
        dput(upperdentry);
 out:
+       revert_creds(old_cred);
        return ERR_PTR(err);
 }