[PATCH] r/o bind mounts: write counts for link/symlink

[AV: add missing nfsd pieces]

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 23 insertions, 1 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 3fbcf2021a2e..00df735fb509 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2387,7 +2387,12 @@ asmlinkage long sys_symlinkat(const char __user *oldname,
         if (IS_ERR(dentry))
                 goto out_unlock;
 
+        error = mnt_want_write(nd.path.mnt);
+        if (error)
+                goto out_dput;
         error = vfs_symlink(nd.path.dentry->d_inode, dentry, from, S_IALLUGO);
+        mnt_drop_write(nd.path.mnt);
+out_dput:
         dput(dentry);
 out_unlock:
         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
@@ -2482,7 +2487,12 @@ asmlinkage long sys_linkat(int olddfd, const char __user *oldname,
         error = PTR_ERR(new_dentry);
         if (IS_ERR(new_dentry))
                 goto out_unlock;
+        error = mnt_want_write(nd.path.mnt);
+        if (error)
+                goto out_dput;
         error = vfs_link(old_nd.path.dentry, nd.path.dentry->d_inode, new_dentry);
+        mnt_drop_write(nd.path.mnt);
+out_dput:
         dput(new_dentry);
 out_unlock:
         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 14d582467029..71f899482306 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1542,6 +1542,10 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
         if (iap && (iap->ia_valid & ATTR_MODE))
                 mode = iap->ia_mode & S_IALLUGO;
 
+        host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+        if (host_err)
+                goto out_nfserr;
+
         if (unlikely(path[plen] != 0)) {
                 char *path_alloced = kmalloc(plen+1, GFP_KERNEL);
                 if (path_alloced == NULL)
@@ -1562,6 +1566,8 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
         err = nfserrno(host_err);
         fh_unlock(fhp);
 
+        mnt_drop_write(fhp->fh_export->ex_path.mnt);
+
         cerr = fh_compose(resfhp, fhp->fh_export, dnew, fhp);
         dput(dnew);
         if (err==0) err = cerr;
@@ -1612,6 +1618,11 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
         dold = tfhp->fh_dentry;
         dest = dold->d_inode;
 
+        host_err = mnt_want_write(tfhp->fh_export->ex_path.mnt);
+        if (host_err) {
+                err = nfserrno(host_err);
+                goto out_dput;
+        }
         host_err = vfs_link(dold, dirp, dnew);
         if (!host_err) {
                 if (EX_ISSYNC(ffhp->fh_export)) {
@@ -1625,7 +1636,8 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
                 else
                         err = nfserrno(host_err);
         }
-
+        mnt_drop_write(tfhp->fh_export->ex_path.mnt);
+out_dput:
         dput(dnew);
 out_unlock:
         fh_unlock(ffhp);