[PATCH 23/27] r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create

Dave Hansen
2007-11-01T23:16:31Z

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.

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

linux-2.6.git-dave/fs/namei.c | 43 +++++++++++++++++++++++++---------
linux-2.6.git-dave/fs/nfsd/vfs.c | 4 +++
linux-2.6.git-dave/net/unix/af_unix.c | 4 +++
3 files changed, 40 insertions(+), 11 deletions(-)

diff -puN fs/namei.c~r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create fs/namei.c
--- linux-2.6.git/fs/namei.c~r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create 2007-11-01 14:46:20.000000000 -0700
+++ linux-2.6.git-dave/fs/namei.c 2007-11-01 14:46:20.000000000 -0700
@@ -2022,6 +2022,23 @@ int vfs_mknod(struct inode *dir, struct
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)
{
@@ -2040,12 +2057,19 @@ asmlinkage long sys_mknodat(int dfd, con
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.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.mnt);
+ if (error)
+ goto out_dput;
+ switch (mode & S_IFMT) {
case 0: case S_IFREG:
error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
break;
@@ -2056,14 +2080,11 @@ asmlinkage long sys_mknodat(int dfd, con
case S_IFIFO: case S_IFSOCK:
error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
break;
- case S_IFDIR:
- error = -EPERM;
- break;
- default:
- error = -EINVAL;
- }
- dput(dentry);
}
+ mnt_drop_write(nd.mnt);
+out_dput:
+ dput(dentry);
+out_unlock:
mutex_unlock(&nd.dentry->d_inode->i_mutex);
path_release(&nd);
out:
diff -puN fs/nfsd/vfs.c~r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create fs/nfsd/vfs.c
--- linux-2.6.git/fs/nfsd/vfs.c~r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create 2007-11-01 14:46:20.000000000 -0700
+++ linux-2.6.git-dave/fs/nfsd/vfs.c 2007-11-01 14:46:20.000000000 -0700
@@ -1242,7 +1242,11 @@ nfsd_create(struct svc_rqst *rqstp, stru
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
+ host_err = mnt_want_write(fhp->fh_export->ex_mnt);
+ if (host_err)
+ break;
host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
+ mnt_drop_write(fhp->fh_export->ex_mnt);
break;
default:
printk("nfsd: bad file type %o in nfsd_create\n", type);
diff -puN net/unix/af_unix.c~r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create net/unix/af_unix.c
--- linux-2.6.git/net/unix/af_unix.c~r-o-bind-mounts-sys_mknodat-elevate-write-count-for-vfs_mknod-create 2007-11-01 14:46:20.000000000 -0700
+++ linux-2.6.git-dave/net/unix/af_unix.c 2007-11-01 14:46:20.000000000 -0700
@@ -838,7 +838,11 @@ 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);
_