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

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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