[PATCH 21/30] r/o bind mounts: get write access for vfs_rename() callers

Dave Hansen
2008-02-15T22:49:28Z

This also uses the little helper in the NFS code to make an if() a little bit
less ugly. We introduced the helper at the beginning of the series.

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: Andrew Morton <akpm@linux-foundation.org>
---

linux-2.6.git-dave/fs/namei.c | 4 ++++
linux-2.6.git-dave/fs/nfsd/vfs.c | 17 +++++++++++++----
2 files changed, 17 insertions(+), 4 deletions(-)

diff -puN fs/namei.c~r-o-bind-mounts-elevate-write-count-over-calls-to-vfs_rename fs/namei.c
--- linux-2.6.git/fs/namei.c~r-o-bind-mounts-elevate-write-count-over-calls-to-vfs_rename 2008-02-15 13:25:54.000000000 -0800
+++ linux-2.6.git-dave/fs/namei.c 2008-02-15 13:25:54.000000000 -0800
@@ -2751,8 +2751,12 @@ static int do_rename(int olddfd, const c
if (new_dentry == trap)
goto exit5;

+ error = mnt_want_write(oldnd.path.mnt);
+ if (error)
+ goto exit5;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry);
+ mnt_drop_write(oldnd.path.mnt);
exit5:
dput(new_dentry);
exit4:
diff -puN fs/nfsd/vfs.c~r-o-bind-mounts-elevate-write-count-over-calls-to-vfs_rename fs/nfsd/vfs.c
--- linux-2.6.git/fs/nfsd/vfs.c~r-o-bind-mounts-elevate-write-count-over-calls-to-vfs_rename 2008-02-15 13:25:54.000000000 -0800
+++ linux-2.6.git-dave/fs/nfsd/vfs.c 2008-02-15 13:25:54.000000000 -0800
@@ -1678,13 +1678,20 @@ nfsd_rename(struct svc_rqst *rqstp, stru
if (ndentry == trap)
goto out_dput_new;

-#ifdef MSNFS
- if ((ffhp->fh_export->ex_flags & NFSEXP_MSNFS) &&
+ if (svc_msnfs(ffhp) &&
((atomic_read(&odentry->d_count) > 1)
|| (atomic_read(&ndentry->d_count) > 1))) {
host_err = -EPERM;
- } else
-#endif
+ goto out_dput_new;
+ }
+
+ host_err = -EXDEV;
+ if (ffhp->fh_export->ex_mnt != tfhp->fh_export->ex_mnt)
+ goto out_dput_new;
+ host_err = mnt_want_write(ffhp->fh_export->ex_mnt);
+ if (host_err)
+ goto out_dput_new;
+
host_err = vfs_rename(fdir, odentry, tdir, ndentry);
if (!host_err && EX_ISSYNC(tfhp->fh_export)) {
host_err = nfsd_sync_dir(tdentry);
@@ -1692,6 +1699,8 @@ nfsd_rename(struct svc_rqst *rqstp, stru
host_err = nfsd_sync_dir(fdentry);
}

+ mnt_drop_write(ffhp->fh_export->ex_mnt);
+
out_dput_new:
dput(ndentry);
out_dput_old:
_