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hostfs: fix races in dentry_name() and inode_name()

Browse Source 
calculating size, then doing allocation, then filling the
path is a Bad Idea(tm), since the ancestors can be renamed,
leading to buffer overrun.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2010-06-06 23:16:34 -04:00
parent c103135c14
commit e9193059b1
1 changed files with 62 additions and 48 deletions
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110
fs/hostfs/hostfs_kern.c
View File

@ -90,44 +90,58 @@ __uml_setup("hostfs=", hostfs_args,
);
#endif
static char *__dentry_name(struct dentry *dentry, char *name)
{
char *p = __dentry_path(dentry, name, PATH_MAX);
char *root;
size_t len;
spin_unlock(&dcache_lock);
root = dentry->d_sb->s_fs_info;
len = strlen(root);
if (IS_ERR(p)) {
__putname(name);
return NULL;
}
strncpy(name, root, PATH_MAX);
if (len > p - name) {
__putname(name);
return NULL;
}
if (p > name + len) {
char *s = name + len;
while ((*s++ = *p++) != '\0')
;
}
return name;
}
static char *dentry_name(struct dentry *dentry)
{
struct dentry *parent;
char *root, *name;
int len;
len = 0;
parent = dentry;
while (parent->d_parent != parent) {
len += parent->d_name.len + 1;
parent = parent->d_parent;
}
root = parent->d_sb->s_fs_info;
len += strlen(root);
name = kmalloc(len + 1, GFP_KERNEL);
if (name == NULL)
char *name = __getname();
if (!name)
return NULL;
name[len] = '\0';
parent = dentry;
while (parent->d_parent != parent) {
len -= parent->d_name.len + 1;
name[len] = '/';
strncpy(&name[len + 1], parent->d_name.name,
parent->d_name.len);
parent = parent->d_parent;
}
strncpy(name, root, strlen(root));
return name;
spin_lock(&dcache_lock);
return __dentry_name(dentry, name); /* will unlock */
}
static char *inode_name(struct inode *ino)
{
struct dentry *dentry;
char *name = __getname();
if (!name)
return NULL;
dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
return dentry_name(dentry);
spin_lock(&dcache_lock);
if (list_empty(&ino->i_dentry)) {
spin_unlock(&dcache_lock);
__putname(name);
return NULL;
}
dentry = list_first_entry(&ino->i_dentry, struct dentry, d_alias);
return __dentry_name(dentry, name); /* will unlock */
}
static char *follow_link(char *link)
@ -272,7 +286,7 @@ int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
if (name == NULL)
return -ENOMEM;
dir = open_dir(name, &error);
kfree(name);
__putname(name);
if (dir == NULL)
return -error;
next = file->f_pos;
@ -318,7 +332,7 @@ int hostfs_file_open(struct inode *ino, struct file *file)
return -ENOMEM;
fd = open_file(name, r, w, append);
kfree(name);
__putname(name);
if (fd < 0)
return fd;
FILE_HOSTFS_I(file)->fd = fd;
@ -532,7 +546,7 @@ int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
else
error = read_name(inode, name);
kfree(name);
__putname(name);
if (error)
goto out_put;
@ -567,7 +581,7 @@ struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
err = read_name(inode, name);
kfree(name);
__putname(name);
if (err == -ENOENT) {
iput(inode);
inode = NULL;
@ -594,12 +608,12 @@ int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
return -ENOMEM;
to_name = dentry_name(to);
if (to_name == NULL) {
kfree(from_name);
__putname(from_name);
return -ENOMEM;
}
err = link_file(to_name, from_name);
kfree(from_name);
kfree(to_name);
__putname(from_name);
__putname(to_name);
return err;
}
@ -614,7 +628,7 @@ int hostfs_unlink(struct inode *ino, struct dentry *dentry)
return -EPERM;
err = unlink_file(file);
kfree(file);
__putname(file);
return err;
}
@ -626,7 +640,7 @@ int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
if ((file = dentry_name(dentry)) == NULL)
return -ENOMEM;
err = make_symlink(file, to);
kfree(file);
__putname(file);
return err;
}
@ -638,7 +652,7 @@ int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
if ((file = dentry_name(dentry)) == NULL)
return -ENOMEM;
err = do_mkdir(file, mode);
kfree(file);
__putname(file);
return err;
}
@ -650,7 +664,7 @@ int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
if ((file = dentry_name(dentry)) == NULL)
return -ENOMEM;
err = do_rmdir(file);
kfree(file);
__putname(file);
return err;
}
@ -673,13 +687,13 @@ int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
init_special_inode(inode, mode, dev);
err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
if (err)
if (!err)
goto out_free;
err = read_name(inode, name);
__putname(name);
if (err)
goto out_put;
kfree(name);
if (err)
goto out_put;
@ -687,7 +701,7 @@ int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
return 0;
out_free:
kfree(name);
__putname(name);
out_put:
iput(inode);
out:
@ -703,12 +717,12 @@ int hostfs_rename(struct inode *from_ino, struct dentry *from,
if ((from_name = dentry_name(from)) == NULL)
return -ENOMEM;
if ((to_name = dentry_name(to)) == NULL) {
kfree(from_name);
__putname(from_name);
return -ENOMEM;
}
err = rename_file(from_name, to_name);
kfree(from_name);
kfree(to_name);
__putname(from_name);
__putname(to_name);
return err;
}
@ -729,7 +743,7 @@ int hostfs_permission(struct inode *ino, int desired)
err = 0;
else
err = access_file(name, r, w, x);
kfree(name);
__putname(name);
if (!err)
err = generic_permission(ino, desired, NULL);
return err;
@ -790,7 +804,7 @@ int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
if (name == NULL)
return -ENOMEM;
err = set_attr(name, &attrs, fd);
kfree(name);
__putname(name);
if (err)
return err;
@ -845,7 +859,7 @@ static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
int err = hostfs_do_readlink(path, link, PATH_MAX);
if (err == PATH_MAX)
err = -E2BIG;
kfree(path);
__putname(path);
}
if (err < 0) {
__putname(link);