[PATCH 19/27] r-o-bind-mounts-elevate-writer-count-for-chown-and-friends

[Dave Hansen <haveblue@us.ibm.com>]

chown/chmod,etc...  don't call permission in the same way that the normal
"open for write" calls do.  They still write to the filesystem, so bump the
write count during these operations.

This conflicts with the current (~2.6.23-rc7) audit git tree in -mm. 
wiggle'ing the patch merges it.

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

 linux-2.6.git-dave/fs/open.c |   39 ++++++++++++++++++++++++++++++---------
 1 file changed, 30 insertions(+), 9 deletions(-)

diff -puN fs/open.c~r-o-bind-mounts-elevate-writer-count-for-chown-and-friends fs/open.c
--- linux-2.6.git/fs/open.c~r-o-bind-mounts-elevate-writer-count-for-chown-and-friends	2007-11-01 14:46:17.000000000 -0700
+++ linux-2.6.git-dave/fs/open.c	2007-11-01 14:46:17.000000000 -0700
@@ -571,12 +571,12 @@ asmlinkage long sys_fchmod(unsigned int 
 
 	audit_inode(NULL, dentry);
 
-	err = -EROFS;
-	if (IS_RDONLY(inode))
+	err = mnt_want_write(file->f_vfsmnt);
+	if (err)
 		goto out_putf;
 	err = -EPERM;
 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
-		goto out_putf;
+		goto out_drop_write;
 	mutex_lock(&inode->i_mutex);
 	if (mode == (mode_t) -1)
 		mode = inode->i_mode;
@@ -585,6 +585,8 @@ asmlinkage long sys_fchmod(unsigned int 
 	err = notify_change(dentry, &newattrs);
 	mutex_unlock(&inode->i_mutex);
 
+out_drop_write:
+	mnt_drop_write(file->f_vfsmnt);
 out_putf:
 	fput(file);
 out:
@@ -604,13 +606,13 @@ asmlinkage long sys_fchmodat(int dfd, co
 		goto out;
 	inode = nd.dentry->d_inode;
 
-	error = -EROFS;
-	if (IS_RDONLY(inode))
+	error = mnt_want_write(nd.mnt);
+	if (error)
 		goto dput_and_out;
 
 	error = -EPERM;
 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
-		goto dput_and_out;
+		goto out_drop_write;
 
 	mutex_lock(&inode->i_mutex);
 	if (mode == (mode_t) -1)
@@ -620,6 +622,8 @@ asmlinkage long sys_fchmodat(int dfd, co
 	error = notify_change(nd.dentry, &newattrs);
 	mutex_unlock(&inode->i_mutex);
 
+out_drop_write:
+	mnt_drop_write(nd.mnt);
 dput_and_out:
 	path_release(&nd);
 out:
@@ -642,9 +646,6 @@ static int chown_common(struct dentry * 
 		printk(KERN_ERR "chown_common: NULL inode\n");
 		goto out;
 	}
-	error = -EROFS;
-	if (IS_RDONLY(inode))
-		goto out;
 	error = -EPERM;
 	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 		goto out;
@@ -675,7 +676,12 @@ asmlinkage long sys_chown(const char __u
 	error = user_path_walk(filename, &nd);
 	if (error)
 		goto out;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto out_release;
 	error = chown_common(nd.dentry, user, group);
+	mnt_drop_write(nd.mnt);
+out_release:
 	path_release(&nd);
 out:
 	return error;
@@ -695,7 +701,12 @@ asmlinkage long sys_fchownat(int dfd, co
 	error = __user_walk_fd(dfd, filename, follow, &nd);
 	if (error)
 		goto out;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto out_release;
 	error = chown_common(nd.dentry, user, group);
+	mnt_drop_write(nd.mnt);
+out_release:
 	path_release(&nd);
 out:
 	return error;
@@ -709,7 +720,12 @@ asmlinkage long sys_lchown(const char __
 	error = user_path_walk_link(filename, &nd);
 	if (error)
 		goto out;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		goto out_release;
 	error = chown_common(nd.dentry, user, group);
+	mnt_drop_write(nd.mnt);
+out_release:
 	path_release(&nd);
 out:
 	return error;
@@ -726,9 +742,14 @@ asmlinkage long sys_fchown(unsigned int 
 	if (!file)
 		goto out;
 
+	error = mnt_want_write(file->f_vfsmnt);
+	if (error)
+		goto out_fput;
 	dentry = file->f_path.dentry;
 	audit_inode(NULL, dentry);
 	error = chown_common(dentry, user, group);
+	mnt_drop_write(file->f_vfsmnt);
+out_fput:
 	fput(file);
 out:
 	return error;
_
-
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