[PATCH 24/28] sys_mknodat(): elevate write count for vfs_mknod/create()

Dave Hansen
2006-08-01T23:54:04Z

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().

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

lxc-dave/fs/namei.c | 12 ++++++++++++
lxc-dave/fs/nfsd/vfs.c | 4 ++++
lxc-dave/net/unix/af_unix.c | 4 ++++
3 files changed, 20 insertions(+)

diff -puN fs/namei.c~C-elevate-writers-vfs_mknod-try2 fs/namei.c
--- lxc/fs/namei.c~C-elevate-writers-vfs_mknod-try2 2006-08-01 16:35:28.000000000 -0700
+++ lxc-dave/fs/namei.c 2006-08-01 16:35:31.000000000 -0700
@@ -1892,14 +1892,26 @@ asmlinkage long sys_mknodat(int dfd, con
if (!IS_ERR(dentry)) {
switch (mode & S_IFMT) {
case 0: case S_IFREG:
+ error = mnt_want_write(nd.mnt);
+ if (error)
+ break;
error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
+ mnt_drop_write(nd.mnt);
break;
case S_IFCHR: case S_IFBLK:
+ error = mnt_want_write(nd.mnt);
+ if (error)
+ break;
error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
new_decode_dev(dev));
+ mnt_drop_write(nd.mnt);
break;
case S_IFIFO: case S_IFSOCK:
+ error = mnt_want_write(nd.mnt);
+ if (error)
+ break;
error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
+ mnt_drop_write(nd.mnt);
break;
case S_IFDIR:
error = -EPERM;
diff -puN fs/nfsd/vfs.c~C-elevate-writers-vfs_mknod-try2 fs/nfsd/vfs.c
--- lxc/fs/nfsd/vfs.c~C-elevate-writers-vfs_mknod-try2 2006-08-01 16:35:27.000000000 -0700
+++ lxc-dave/fs/nfsd/vfs.c 2006-08-01 16:35:31.000000000 -0700
@@ -1155,6 +1155,9 @@ nfsd_create(struct svc_rqst *rqstp, stru
/*
* Get the dir op function pointer.
*/
+ err = mnt_want_write(fhp->fh_export->ex_mnt);
+ if (err)
+ goto out_nfserr;
err = nfserr_perm;
switch (type) {
case S_IFREG:
@@ -1173,6 +1176,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
printk("nfsd: bad file type %o in nfsd_create\n", type);
err = -EINVAL;
}
+ mnt_drop_write(fhp->fh_export->ex_mnt);
if (err < 0)
goto out_nfserr;

diff -puN net/unix/af_unix.c~C-elevate-writers-vfs_mknod-try2 net/unix/af_unix.c
--- lxc/net/unix/af_unix.c~C-elevate-writers-vfs_mknod-try2 2006-08-01 16:35:27.000000000 -0700
+++ lxc-dave/net/unix/af_unix.c 2006-08-01 16:35:31.000000000 -0700
@@ -821,7 +821,11 @@ static int unix_bind(struct socket *sock
*/
mode = S_IFSOCK |
(SOCK_INODE(sock)->i_mode & ~current->fs->umask);
+ err = mnt_want_write(nd.mnt);
+ if (err)
+ goto out_mknod_dput;
err = vfs_mknod(nd.dentry->d_inode, dentry, mode, 0);
+ mnt_drop_write(nd.mnt);
if (err)
goto out_mknod_dput;
mutex_unlock(&nd.dentry->d_inode->i_mutex);
_