[PATCH 10/27] r-o-bind-mounts-elevate-mount-count-for-extended-attributes

[Dave Hansen]

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

Acked-by: Christoph Hellwig <[EMAIL PROTECTED]>
Signed-off-by: Dave Hansen <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---

 linux-2.6.git-dave/fs/nfsd/nfs4proc.c |    7 ++++++-
 linux-2.6.git-dave/fs/xattr.c         |   16 ++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff -puN 
fs/nfsd/nfs4proc.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes 
fs/nfsd/nfs4proc.c
--- 
linux-2.6.git/fs/nfsd/nfs4proc.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes
        2007-11-01 14:46:11.000000000 -0700
+++ linux-2.6.git-dave/fs/nfsd/nfs4proc.c       2007-11-01 14:46:11.000000000 
-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~r-o-bind-mounts-elevate-mount-count-for-extended-attributes 
fs/xattr.c
--- 
linux-2.6.git/fs/xattr.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes
        2007-11-01 14:46:11.000000000 -0700
+++ linux-2.6.git-dave/fs/xattr.c       2007-11-01 14:46:11.000000000 -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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