From 18f335aff86913de3c76f88d32c8135c1da62ce6 Mon Sep 17 00:00:00 2001
From: Dave Hansen <haveblue@us.ibm.com>
Date: Fri, 15 Feb 2008 14:37:38 -0800
Subject: [PATCH] [PATCH] r/o bind mounts: elevate write count for
xattr_permission() callers
This basically audits the callers of xattr_permission(), which calls
permission() and can perform writes to the filesystem.
[AV: add missing parts - removexattr() and nfsd posix acls, plug for a leak
spotted by Miklos]
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>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/nfsd/nfs4proc.c | 7 ++++++-
fs/nfsd/vfs.c | 4 ++++
fs/xattr.c | 40 ++++++++++++++++++++++++++++++++--------
3 files changed, 42 insertions(+), 9 deletions(-)
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index c593db047d8b..c309c881bd4e 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -658,14 +658,19 @@ nfsd4_setattr(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
return status;
}
}
+ status = mnt_want_write(cstate->current_fh.fh_export->ex_path.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_path.mnt);
return status;
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 18a4cc9feeb3..626dfd38528f 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -2086,6 +2086,9 @@ nfsd_set_posix_acl(struct svc_fh *fhp, int type, struct posix_acl *acl)
} else
size = 0;
+ error = mnt_want_write(fhp->fh_export->ex_path.mnt);
+ if (error)
+ goto getout;
if (size)
error = vfs_setxattr(fhp->fh_dentry, name, value, size, 0);
else {
@@ -2097,6 +2100,7 @@ nfsd_set_posix_acl(struct svc_fh *fhp, int type, struct posix_acl *acl)
error = 0;
}
}
+ mnt_drop_write(fhp->fh_export->ex_path.mnt);
getout:
kfree(value);
diff --git a/fs/xattr.c b/fs/xattr.c
index 3acab1615460..f7062da505d4 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -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, const char *name, int mask)
* 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;
}
@@ -262,7 +261,11 @@ sys_setxattr(char __user *path, char __user *name, void __user *value,
error = user_path_walk(path, &nd);
if (error)
return error;
- error = setxattr(nd.path.dentry, name, value, size, flags);
+ error = mnt_want_write(nd.path.mnt);
+ if (!error) {
+ error = setxattr(nd.path.dentry, name, value, size, flags);
+ mnt_drop_write(nd.path.mnt);
+ }
path_put(&nd.path);
return error;
}
@@ -277,7 +280,11 @@ sys_lsetxattr(char __user *path, char __user *name, void __user *value,
error = user_path_walk_link(path, &nd);
if (error)
return error;
- error = setxattr(nd.path.dentry, name, value, size, flags);
+ error = mnt_want_write(nd.path.mnt);
+ if (!error) {
+ error = setxattr(nd.path.dentry, name, value, size, flags);
+ mnt_drop_write(nd.path.mnt);
+ }
path_put(&nd.path);
return error;
}
@@ -295,7 +302,12 @@ sys_fsetxattr(int fd, char __user *name, void __user *value,
return error;
dentry = f->f_path.dentry;
audit_inode(NULL, dentry);
- error = setxattr(dentry, name, value, size, flags);
+ error = mnt_want_write(f->f_path.mnt);
+ if (!error) {
+ error = setxattr(dentry, name, value, size, flags);
+ mnt_drop_write(f->f_path.mnt);
+ }
+out_fput:
fput(f);
return error;
}
@@ -482,7 +494,11 @@ sys_removexattr(char __user *path, char __user *name)
error = user_path_walk(path, &nd);
if (error)
return error;
- error = removexattr(nd.path.dentry, name);
+ error = mnt_want_write(nd.path.mnt);
+ if (!error) {
+ error = removexattr(nd.path.dentry, name);
+ mnt_drop_write(nd.path.mnt);
+ }
path_put(&nd.path);
return error;
}
@@ -496,7 +512,11 @@ sys_lremovexattr(char __user *path, char __user *name)
error = user_path_walk_link(path, &nd);
if (error)
return error;
- error = removexattr(nd.path.dentry, name);
+ error = mnt_want_write(nd.path.mnt);
+ if (!error) {
+ error = removexattr(nd.path.dentry, name);
+ mnt_drop_write(nd.path.mnt);
+ }
path_put(&nd.path);
return error;
}
@@ -513,7 +533,11 @@ sys_fremovexattr(int fd, char __user *name)
return error;
dentry = f->f_path.dentry;
audit_inode(NULL, dentry);
- error = removexattr(dentry, name);
+ error = mnt_want_write(f->f_path.mnt);
+ if (!error) {
+ error = removexattr(dentry, name);
+ mnt_drop_write(f->f_path.mnt);
+ }
fput(f);
return error;
}