[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>

1 files changed, 37 insertions, 11 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);