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[PATCH 12/24] elevate mount count for extended attributes

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From: Dave Hansen <haveblue@...>
To: <akpm@...>
Cc: <linux-kernel@...>, <hch@...>, Dave Hansen <haveblue@...>
Subject: [PATCH 12/24] elevate mount count for extended attributes
Date: Monday, September 17, 2007 - 2:27 pm

This basically audits the callers of xattr_permission(), which
calls permission() and can perform writes to the filesystem.

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

 lxc-dave/fs/nfsd/nfs4proc.c |    7 ++++++-
 lxc-dave/fs/xattr.c         |   16 ++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff -puN fs/nfsd/nfs4proc.c~elevate-mount-count-for-extended-attributes fs/nfsd/nfs4proc.c
--- lxc/fs/nfsd/nfs4proc.c~elevate-mount-count-for-extended-attributes	2007-09-17 09:44:03.000000000 -0700
+++ lxc-dave/fs/nfsd/nfs4proc.c	2007-09-17 09:44:03.000000000 -0700
@@ -658,14 +658,19 @@ nfsd4_setattr(struct svc_rqst *rqstp, st
 			return status;
 		}
 	}
+	status = mnt_want_write(cstate->current_fh.fh_export->ex_mnt);
+	if (status)
+		return status;
 	status = nfs_ok;
 	if (setattr->sa_acl != NULL)
 		status = nfsd4_set_nfs4_acl(rqstp, &cstate->current_fh,
 					    setattr->sa_acl);
 	if (status)
-		return status;
+		goto out;
 	status = nfsd_setattr(rqstp, &cstate->current_fh, &setattr->sa_iattr,
 				0, (time_t)0);
+out:
+	mnt_drop_write(cstate->current_fh.fh_export->ex_mnt);
 	return status;
 }
 
diff -puN fs/xattr.c~elevate-mount-count-for-extended-attributes fs/xattr.c
--- lxc/fs/xattr.c~elevate-mount-count-for-extended-attributes	2007-09-17 09:44:03.000000000 -0700
+++ lxc-dave/fs/xattr.c	2007-09-17 09:44:03.000000000 -0700
@@ -11,6 +11,7 @@
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/xattr.h>
+#include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
@@ -32,8 +33,6 @@ xattr_permission(struct inode *inode, co
 	 * filesystem  or on an immutable / append-only inode.
 	 */
 	if (mask & MAY_WRITE) {
-		if (IS_RDONLY(inode))
-			return -EROFS;
 		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 			return -EPERM;
 	}
@@ -235,7 +234,11 @@ sys_setxattr(char __user *path, char __u
 	error = user_path_walk(path, &nd);
 	if (error)
 		return error;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		return error;
 	error = setxattr(nd.dentry, name, value, size, flags);
+	mnt_drop_write(nd.mnt);
 	path_release(&nd);
 	return error;
 }
@@ -250,7 +253,11 @@ sys_lsetxattr(char __user *path, char __
 	error = user_path_walk_link(path, &nd);
 	if (error)
 		return error;
+	error = mnt_want_write(nd.mnt);
+	if (error)
+		return error;
 	error = setxattr(nd.dentry, name, value, size, flags);
+	mnt_drop_write(nd.mnt);
 	path_release(&nd);
 	return error;
 }
@@ -266,9 +273,14 @@ sys_fsetxattr(int fd, char __user *name,
 	f = fget(fd);
 	if (!f)
 		return error;
+	error = mnt_want_write(f->f_vfsmnt);
+	if (error)
+		goto out_fput;
 	dentry = f->f_path.dentry;
 	audit_inode(NULL, dentry);
 	error = setxattr(dentry, name, value, size, flags);
+	mnt_drop_write(f->f_vfsmnt);
+out_fput:
 	fput(f);
 	return error;
 }
_
-
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Messages in current thread:
[PATCH 00/24] Read-only bind mounts, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 00/24] Read-only bind mounts, Christoph Hellwig, (Wed Sep 19, 1:44 pm)
Re: [PATCH 00/24] Read-only bind mounts, Andrew Morton, (Wed Sep 19, 5:24 pm)
Re: [PATCH 00/24] Read-only bind mounts, Dave Hansen, (Wed Sep 19, 5:56 pm)
Re: [PATCH 00/24] Read-only bind mounts, Andrew Morton, (Wed Sep 19, 6:06 pm)
Re: [PATCH 00/24] Read-only bind mounts, Miklos Szeredi, (Thu Sep 20, 5:58 am)
Re: [PATCH 00/24] Read-only bind mounts, Serge E. Hallyn, (Wed Sep 19, 10:21 am)
[PATCH 14/24] unix_find_other() elevate write count for touc..., Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 14/24] unix_find_other() elevate write count for ..., Christoph Hellwig, (Wed Sep 19, 1:35 pm)
[PATCH 22/24] do_rmdir(): elevate write count, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 22/24] do_rmdir(): elevate write count, Christoph Hellwig, (Wed Sep 19, 1:39 pm)
[PATCH 21/24] elevate mnt writers for vfs_unlink() callers, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 21/24] elevate mnt writers for vfs_unlink() callers, Christoph Hellwig, (Wed Sep 19, 1:38 pm)
[PATCH 19/24] elevate write count for do_sys_utime() and tou..., Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 19/24] elevate write count for do_sys_utime() and..., Christoph Hellwig, (Wed Sep 19, 1:36 pm)
[PATCH 20/24] sys_mknodat(): elevate write count for vfs_mkn..., Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 20/24] sys_mknodat(): elevate write count for vfs..., Christoph Hellwig, (Wed Sep 19, 1:38 pm)
[PATCH 09/24] elevate mnt writers for callers of vfs_mkdir(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 09/24] elevate mnt writers for callers of vfs_mkd..., Christoph Hellwig, (Wed Sep 19, 1:32 pm)
[PATCH 04/24] r/o bind mounts: stub functions, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 04/24] r/o bind mounts: stub functions, Christoph Hellwig, (Wed Sep 19, 1:28 pm)
[PATCH 11/24] elevate write count for link and symlink calls, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 11/24] elevate write count for link and symlink c..., Christoph Hellwig, (Wed Sep 19, 1:33 pm)
[PATCH 06/24] r/o bind mounts: elevate write count for some ..., Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 06/24] r/o bind mounts: elevate write count for s..., Christoph Hellwig, (Wed Sep 19, 1:31 pm)
[PATCH 18/24] elevate write count for do_utimes(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 18/24] elevate write count for do_utimes(), Christoph Hellwig, (Wed Sep 19, 1:36 pm)
[PATCH 16/24] nfs: check mnt instead of superblock directly, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 16/24] nfs: check mnt instead of superblock direc..., Christoph Hellwig, (Wed Sep 19, 1:36 pm)
[PATCH 17/24] elevate writer count for do_sys_truncate(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 17/24] elevate writer count for do_sys_truncate(), Christoph Hellwig, (Wed Sep 19, 1:36 pm)
[PATCH 15/24] elevate write count over calls to vfs_rename(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 15/24] elevate write count over calls to vfs_rena..., Christoph Hellwig, (Wed Sep 19, 1:35 pm)
[PATCH 12/24] elevate mount count for extended attributes, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 12/24] elevate mount count for extended attributes, Christoph Hellwig, (Wed Sep 19, 1:34 pm)
[PATCH 10/24] elevate write count during entire ncp_ioctl(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 10/24] elevate write count during entire ncp_ioct..., Christoph Hellwig, (Wed Sep 19, 1:33 pm)
[PATCH 01/24] filesystem helpers for custom 'struct file's, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 01/24] filesystem helpers for custom 'struct file's, Christoph Hellwig, (Wed Sep 19, 1:26 pm)
[PATCH] docuement filesystem helpers for custom 'struct file's, Dave Hansen, (Wed Sep 19, 1:47 pm)
Re: [PATCH] docuement filesystem helpers for custom 'struct ..., Randy Dunlap, (Wed Sep 19, 6:07 pm)
Re: [PATCH] docuement filesystem helpers for custom 'struct ..., Dave Hansen, (Thu Sep 20, 1:25 pm)
Re: [PATCH] docuement filesystem helpers for custom 'struct ..., Christoph Hellwig, (Thu Sep 20, 1:30 pm)
[PATCH 05/24] elevate write count open()'d files, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 05/24] elevate write count open()'d files, Christoph Hellwig, (Wed Sep 19, 1:30 pm)
[PATCH 07/24] elevate writer count for chown and friends, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 07/24] elevate writer count for chown and friends, Christoph Hellwig, (Wed Sep 19, 1:31 pm)
[PATCH 13/24] elevate write count for file_update_time(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 13/24] elevate write count for file_update_time(), Christoph Hellwig, (Wed Sep 19, 1:35 pm)
[PATCH 08/24] make access() use mnt check, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 08/24] make access() use mnt check, Christoph Hellwig, (Wed Sep 19, 1:32 pm)
[PATCH 03/24] create cleanup helper svc_msnfs(), Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 03/24] create cleanup helper svc_msnfs(), Jan Engelhardt, (Wed Sep 19, 1:39 pm)
Re: [PATCH 03/24] create cleanup helper svc_msnfs(), Dave Hansen, (Wed Sep 19, 1:45 pm)
Re: [PATCH 03/24] create cleanup helper svc_msnfs(), Trond Myklebust, (Wed Sep 19, 1:54 pm)
Re: [PATCH 03/24] create cleanup helper svc_msnfs(), Christoph Hellwig, (Wed Sep 19, 1:59 pm)
Re: [PATCH 03/24] create cleanup helper svc_msnfs(), Trond Myklebust, (Wed Sep 19, 2:10 pm)
Re: [PATCH 03/24] create cleanup helper svc_msnfs(), Christoph Hellwig, (Wed Sep 19, 1:28 pm)
[PATCH 02/24] rearrange may_open() to be r/o friendly, Dave Hansen, (Mon Sep 17, 2:27 pm)
Re: [PATCH 02/24] rearrange may_open() to be r/o friendly, Christoph Hellwig, (Wed Sep 19, 1:27 pm)
Re: [PATCH 02/24] rearrange may_open() to be r/o friendly, Dave Hansen, (Thu Sep 20, 2:47 pm)