From ab92a20bce3b4c21927cc1ae514c482f50ad3487 Mon Sep 17 00:00:00 2001
From: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Date: Tue, 18 Aug 2015 12:38:36 +0800
Subject: [PATCH] ubifs: make ubifs_[get|set]xattr atomic
This commit make the ubifs_[get|set]xattr protected by ui_mutex.
Originally, there is a possibility that ubifs_getxattr to get
a wrong value.
P1 P2
---------- ----------
ubifs_getxattr ubifs_setxattr
- kfree()
- memcpy()
- kmemdup()
Then ubifs_getxattr() would get a non-sense data. To solve this
problem, this commit make the xattr of ubifs_inode updated in
atomic.
Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
---
fs/ubifs/xattr.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index 96f3448b6eb4..99364aeed035 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -200,6 +200,7 @@ static int change_xattr(struct ubifs_info *c, struct inode *host,
int err;
struct ubifs_inode *host_ui = ubifs_inode(host);
struct ubifs_inode *ui = ubifs_inode(inode);
+ void *buf = NULL;
struct ubifs_budget_req req = { .dirtied_ino = 2,
.dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
@@ -208,14 +209,17 @@ static int change_xattr(struct ubifs_info *c, struct inode *host,
if (err)
return err;
- kfree(ui->data);
- ui->data = kmemdup(value, size, GFP_NOFS);
- if (!ui->data) {
+ buf = kmemdup(value, size, GFP_NOFS);
+ if (!buf) {
err = -ENOMEM;
goto out_free;
}
+ mutex_lock(&ui->ui_mutex);
+ kfree(ui->data);
+ ui->data = buf;
inode->i_size = ui->ui_size = size;
ui->data_len = size;
+ mutex_unlock(&ui->ui_mutex);
mutex_lock(&host_ui->ui_mutex);
host->i_ctime = ubifs_current_time(host);
@@ -409,6 +413,7 @@ ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
ubifs_assert(inode->i_size == ui->data_len);
ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
+ mutex_lock(&ui->ui_mutex);
if (buf) {
/* If @buf is %NULL we are supposed to return the length */
if (ui->data_len > size) {
@@ -423,6 +428,7 @@ ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
err = ui->data_len;
out_iput:
+ mutex_unlock(&ui->ui_mutex);
iput(inode);
out_unlock:
kfree(xent);