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ubifs: make ubifs_[get|set]xattr atomic

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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>
This commit is contained in:
Dongsheng Yang 2015-08-18 12:38:36 +08:00 committed by Richard Weinberger
parent 54bcfdf19e
commit ab92a20bce
1 changed files with 9 additions and 3 deletions
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12
fs/ubifs/xattr.c
View file

@ -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);