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fix buggered locking in bch2_ioctl_subvolume_destroy()

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Merge tag 'pull-bcachefs-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull bcachefs locking fix from Al Viro:
 "Fix broken locking in bch2_ioctl_subvolume_destroy()"

* tag 'pull-bcachefs-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  bch2_ioctl_subvolume_destroy(): fix locking
  new helper: user_path_locked_at()
This commit is contained in:
Linus Torvalds 2024-01-12 18:04:01 -08:00
commit f16ab99c2e
3 changed files with 31 additions and 17 deletions
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31
fs/bcachefs/fs-ioctl.c
View File

@ -443,33 +443,36 @@ static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,
static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
struct bch_ioctl_subvolume arg)
{
const char __user *name = (void __user *)(unsigned long)arg.dst_ptr;
struct path path;
struct inode *dir;
struct dentry *victim;
int ret = 0;
if (arg.flags)
return -EINVAL;
ret = user_path_at(arg.dirfd,
(const char __user *)(unsigned long)arg.dst_ptr,
LOOKUP_FOLLOW, &path);
if (ret)
return ret;
victim = user_path_locked_at(arg.dirfd, name, &path);
if (IS_ERR(victim))
return PTR_ERR(victim);
if (path.dentry->d_sb->s_fs_info != c) {
if (victim->d_sb->s_fs_info != c) {
ret = -EXDEV;
goto err;
}
dir = path.dentry->d_parent->d_inode;
ret = __bch2_unlink(dir, path.dentry, true);
if (ret)
if (!d_is_positive(victim)) {
ret = -ENOENT;
goto err;
fsnotify_rmdir(dir, path.dentry);
d_delete(path.dentry);
}
dir = d_inode(path.dentry);
ret = __bch2_unlink(dir, victim, true);
if (!ret) {
fsnotify_rmdir(dir, victim);
d_delete(victim);
}
inode_unlock(dir);
err:
dput(victim);
path_put(&path);
return ret;
}

16
fs/namei.c
View File

@ -2572,13 +2572,13 @@ static int filename_parentat(int dfd, struct filename *name,
}
/* does lookup, returns the object with parent locked */
static struct dentry *__kern_path_locked(struct filename *name, struct path *path)
static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct path *path)
{
struct dentry *d;
struct qstr last;
int type, error;
error = filename_parentat(AT_FDCWD, name, 0, path, &last, &type);
error = filename_parentat(dfd, name, 0, path, &last, &type);
if (error)
return ERR_PTR(error);
if (unlikely(type != LAST_NORM)) {
@ -2597,12 +2597,22 @@ static struct dentry *__kern_path_locked(struct filename *name, struct path *pat
struct dentry *kern_path_locked(const char *name, struct path *path)
{
struct filename *filename = getname_kernel(name);
struct dentry *res = __kern_path_locked(filename, path);
struct dentry *res = __kern_path_locked(AT_FDCWD, filename, path);
putname(filename);
return res;
}
struct dentry *user_path_locked_at(int dfd, const char __user *name, struct path *path)
{
struct filename *filename = getname(name);
struct dentry *res = __kern_path_locked(dfd, filename, path);
putname(filename);
return res;
}
EXPORT_SYMBOL(user_path_locked_at);
int kern_path(const char *name, unsigned int flags, struct path *path)
{
struct filename *filename = getname_kernel(name);

1
include/linux/namei.h
View File

@ -66,6 +66,7 @@ extern struct dentry *kern_path_create(int, const char *, struct path *, unsigne
extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
extern void done_path_create(struct path *, struct dentry *);
extern struct dentry *kern_path_locked(const char *, struct path *);
extern struct dentry *user_path_locked_at(int , const char __user *, struct path *);
int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
struct path *parent, struct qstr *last, int *type,
const struct path *root);