[PATCH] r/o bind mounts: get callers of vfs_mknod/create/mkdir()

This takes care of all of the direct callers of vfs_mknod().
Since a few of these cases also handle normal file creation
as well, this also covers some calls to vfs_create().

So that we don't have to make three mnt_want/drop_write()
calls inside of the switch statement, we move some of its
logic outside of the switch and into a helper function
suggested by Christoph.

This also encapsulates a fix for mknod(S_IFREG) that Miklos
found.

[AV: merged mkdir handling, added missing nfsd pieces]

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 63 insertions, 13 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 89ef3178eaaa..3fbcf2021a2e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1984,6 +1984,23 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
         return error;
 }
 
+static int may_mknod(mode_t mode)
+{
+        switch (mode & S_IFMT) {
+        case S_IFREG:
+        case S_IFCHR:
+        case S_IFBLK:
+        case S_IFIFO:
+        case S_IFSOCK:
+        case 0: /* zero mode translates to S_IFREG */
+                return 0;
+        case S_IFDIR:
+                return -EPERM;
+        default:
+                return -EINVAL;
+        }
+}
+
 asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
                                 unsigned dev)
 {
@@ -2002,12 +2019,19 @@ asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
         if (error)
                 goto out;
         dentry = lookup_create(&nd, 0);
-        error = PTR_ERR(dentry);
-
+        if (IS_ERR(dentry)) {
+                error = PTR_ERR(dentry);
+                goto out_unlock;
+        }
         if (!IS_POSIXACL(nd.path.dentry->d_inode))
                 mode &= ~current->fs->umask;
-        if (!IS_ERR(dentry)) {
-                switch (mode & S_IFMT) {
+        error = may_mknod(mode);
+        if (error)
+                goto out_dput;
+        error = mnt_want_write(nd.path.mnt);
+        if (error)
+                goto out_dput;
+        switch (mode & S_IFMT) {
                 case 0: case S_IFREG:
                         error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
                         break;
@@ -2018,14 +2042,11 @@ asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
                 case S_IFIFO: case S_IFSOCK:
                         error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
                         break;
-                case S_IFDIR:
-                        error = -EPERM;
-                        break;
-                default:
-                        error = -EINVAL;
-                }
-                dput(dentry);
         }
+        mnt_drop_write(nd.path.mnt);
+out_dput:
+        dput(dentry);
+out_unlock:
         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
         path_put(&nd.path);
 out:
@@ -2083,7 +2104,12 @@ asmlinkage long sys_mkdirat(int dfd, const char __user *pathname, int mode)
 
         if (!IS_POSIXACL(nd.path.dentry->d_inode))
                 mode &= ~current->fs->umask;
+        error = mnt_want_write(nd.path.mnt);
+        if (error)
+                goto out_dput;
         error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
+        mnt_drop_write(nd.path.mnt);
+out_dput:
         dput(dentry);
 out_unlock:
         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 4e77a1a3bd73..145b3c877a27 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -155,7 +155,11 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
                 dprintk("NFSD: nfsd4_create_clid_dir: DIRECTORY EXISTS\n");
                 goto out_put;
         }
+        status = mnt_want_write(rec_dir.path.mnt);
+        if (status)
+                goto out_put;
         status = vfs_mkdir(rec_dir.path.dentry->d_inode, dentry, S_IRWXU);
+        mnt_drop_write(rec_dir.path.mnt);
 out_put:
         dput(dentry);
 out_unlock:
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index efff58a5818c..14d582467029 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1255,23 +1255,35 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
         err = 0;
         switch (type) {
         case S_IFREG:
+                host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+                if (host_err)
+                        goto out_nfserr;
                 host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
                 break;
         case S_IFDIR:
+                host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+                if (host_err)
+                        goto out_nfserr;
                 host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
                 break;
         case S_IFCHR:
         case S_IFBLK:
         case S_IFIFO:
         case S_IFSOCK:
+                host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+                if (host_err)
+                        goto out_nfserr;
                 host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
                 break;
         default:
                 printk("nfsd: bad file type %o in nfsd_create\n", type);
                 host_err = -EINVAL;
+                goto out_nfserr;
         }
-        if (host_err < 0)
+        if (host_err < 0) {
+                mnt_drop_write(fhp->fh_export->ex_path.mnt);
                 goto out_nfserr;
+        }
 
         if (EX_ISSYNC(fhp->fh_export)) {
                 err = nfserrno(nfsd_sync_dir(dentry));
@@ -1282,6 +1294,7 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
         err2 = nfsd_create_setattr(rqstp, resfhp, iap);
         if (err2)
                 err = err2;
+        mnt_drop_write(fhp->fh_export->ex_path.mnt);
         /*
          * Update the file handle to get the new inode info.
          */
@@ -1359,6 +1372,9 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 v_atime = verifier[1]&0x7fffffff;
         }
         
+        host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
+        if (host_err)
+                goto out_nfserr;
         if (dchild->d_inode) {
                 err = 0;
 
@@ -1390,12 +1406,15 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 case NFS3_CREATE_GUARDED:
                         err = nfserr_exist;
                 }
+                mnt_drop_write(fhp->fh_export->ex_path.mnt);
                 goto out;
         }
 
         host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
-        if (host_err < 0)
+        if (host_err < 0) {
+                mnt_drop_write(fhp->fh_export->ex_path.mnt);
                 goto out_nfserr;
+        }
         if (created)
                 *created = 1;
 
@@ -1420,6 +1439,7 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
         if (err2)
                 err = err2;
 
+        mnt_drop_write(fhp->fh_export->ex_path.mnt);
         /*
          * Update the filehandle to get the new inode info.
          */