vfs: replace calling i_op->readlink with vfs_readlink()

Also check d_is_symlink() in callers instead of inode->i_op->readlink
because following patches will allow NULL ->readlink for symlinks.

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

diff --git a/fs/namei.c b/fs/namei.c
index 5b4eed2..12a4159 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4668,6 +4668,27 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 }
 EXPORT_SYMBOL(generic_readlink);
 
+/**
+ * vfs_readlink - copy symlink body into userspace buffer
+ * @dentry: dentry on which to get symbolic link
+ * @buffer: user memory pointer
+ * @buflen: size of buffer
+ *
+ * Does not touch atime.  That's up to the caller if necessary
+ *
+ * Does not call security hook.
+ */
+int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+       struct inode *inode = d_inode(dentry);
+
+       if (!inode->i_op->readlink)
+               return -EINVAL;
+
+       return inode->i_op->readlink(dentry, buffer, buflen);
+}
+EXPORT_SYMBOL(vfs_readlink);
+
 /**
  * vfs_get_link - get symlink body
  * @dentry: dentry on which to get symbolic link

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index c2d2895..645e1e3 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3576,10 +3576,10 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
        if (!p)
                return nfserr_resource;
        /*
-        * XXX: By default, the ->readlink() VFS op will truncate symlinks
-        * if they would overflow the buffer.  Is this kosher in NFSv4?  If
-        * not, one easy fix is: if ->readlink() precisely fills the buffer,
-        * assume that truncation occurred, and return NFS4ERR_RESOURCE.
+        * XXX: By default, vfs_readlink() will truncate symlinks if they
+        * would overflow the buffer.  Is this kosher in NFSv4?  If not, one
+        * easy fix is: if vfs_readlink() precisely fills the buffer, assume
+        * that truncation occurred, and return NFS4ERR_RESOURCE.
         */
        nfserr = nfsd_readlink(readlink->rl_rqstp, readlink->rl_fhp,
                                                (char *)p, &maxcount);

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 8ca642f..b854f02 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1451,7 +1451,6 @@ do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 __be32
 nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
 {
-       struct inode    *inode;
        mm_segment_t    oldfs;
        __be32          err;
        int             host_err;
@@ -1463,10 +1462,9 @@ nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
 
        path.mnt = fhp->fh_export->ex_path.mnt;
        path.dentry = fhp->fh_dentry;
-       inode = d_inode(path.dentry);
 
        err = nfserr_inval;
-       if (!inode->i_op->readlink)
+       if (!d_is_symlink(path.dentry))
                goto out;
 
        touch_atime(&path);
@@ -1475,7 +1473,7 @@ nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
         */
 
        oldfs = get_fs(); set_fs(KERNEL_DS);
-       host_err = inode->i_op->readlink(path.dentry, (char __user *)buf, *lenp);
+       host_err = vfs_readlink(path.dentry, (char __user *)buf, *lenp);
        set_fs(oldfs);
 
        if (host_err < 0)

diff --git a/fs/stat.c b/fs/stat.c
index bc045c7..0b210c3 100644 (file)
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -329,12 +329,14 @@ retry:
                struct inode *inode = d_backing_inode(path.dentry);
 
                error = empty ? -ENOENT : -EINVAL;
-               if (inode->i_op->readlink) {
+               /*
+                * AFS mountpoints allow readlink(2) but are not symlinks
+                */
+               if (d_is_symlink(path.dentry) || inode->i_op->readlink) {
                        error = security_inode_readlink(path.dentry);
                        if (!error) {
                                touch_atime(&path);
-                               error = inode->i_op->readlink(path.dentry,
-                                                             buf, bufsiz);
+                               error = vfs_readlink(path.dentry, buf, bufsiz);
                        }
                }
                path_put(&path);

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index c245bed..9b12f7c 100644 (file)
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -287,7 +287,7 @@ xfs_readlink_by_handle(
                return PTR_ERR(dentry);
 
        /* Restrict this handle operation to symlinks only. */
-       if (!d_inode(dentry)->i_op->readlink) {
+       if (!d_is_symlink(dentry)) {
                error = -EINVAL;
                goto out_dput;
        }
@@ -297,7 +297,7 @@ xfs_readlink_by_handle(
                goto out_dput;
        }
 
-       error = d_inode(dentry)->i_op->readlink(dentry, hreq->ohandle, olen);
+       error = vfs_readlink(dentry, hreq->ohandle, olen);
 
  out_dput:
        dput(dentry);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index dc0478c..eba20d1 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2935,6 +2935,7 @@ extern int vfs_lstat(const char __user *, struct kstat *);
 extern int vfs_fstat(unsigned int, struct kstat *);
 extern int vfs_fstatat(int , const char __user *, struct kstat *, int);
 extern const char *vfs_get_link(struct dentry *, struct delayed_call *);
+extern int vfs_readlink(struct dentry *, char __user *, int);
 
 extern int __generic_block_fiemap(struct inode *inode,
                                  struct fiemap_extent_info *fieinfo,