On Sat, Dec 02, 2023 at 10:27:06PM +0000, Al Viro wrote:
> On Sat, Dec 02, 2023 at 01:22:15PM -0800, Kees Cook wrote:
>
> > static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
> > {
> > @@ -338,9 +339,8 @@ int pstore_mkfile(struct dentry *root, struct
> > pstore_record *record)
> > {
> > struct dentry *dentry;
> > struct inode *inode __free(iput) = NULL;
> > - int rc = 0;
> > char name[PSTORE_NAMELEN];
> > - struct pstore_private *private, *pos;
> > + struct pstore_private *private __free(pstore_private) = NULL, *pos;
> > size_t size = record->size + record->ecc_notice_size;
> >
> > if (WARN_ON(!inode_is_locked(d_inode(root))))
> > @@ -356,7 +356,6 @@ int pstore_mkfile(struct dentry *root, struct
> > pstore_record *record)
> > return -EEXIST;
> > }
> >
> > - rc = -ENOMEM;
> > inode = pstore_get_inode(root->d_sb);
> > if (!inode)
> > return -ENOMEM;
> > @@ -373,7 +372,7 @@ int pstore_mkfile(struct dentry *root, struct
> > pstore_record *record)
> >
> > dentry = d_alloc_name(root, name);
> > if (!dentry)
> > - goto fail_private;
> > + return -ENOMEM;
> >
> > private->dentry = dentry;
> > private->record = record;
> > @@ -386,13 +385,9 @@ int pstore_mkfile(struct dentry *root, struct
> > pstore_record *record)
> >
> > d_add(dentry, no_free_ptr(inode));
> >
> > - list_add(&private->list, &records_list);
> > + list_add(&(no_free_ptr(private))->list, &records_list);
>
> That's really brittle. It critically depends upon having no failure
> exits past the assignment to ->i_private; once you've done that,
> you have transferred the ownership of that thing to the inode
> (look at your ->evict_inode()).
I guess so, but it was already that way, and it isn't assignment to
i_private until everything else is "done", apart from adding to the
dentry and the pstore internal list.
> But you can't say
> inode->i_private = no_free_ptr(private);
> since you are using private past that point.
True. How about this reordering:
if (record->time.tv_sec)
inode_set_mtime_to_ts(inode,
inode_set_ctime_to_ts(inode,
record->time));
list_add(&private->list, &records_list);
inode->i_private = no_free_ptr(private);
d_add(dentry, no_free_ptr(inode));
But none of this gets into how you'd like to see the iput handled. If
you'd prefer, I can just define a pstore_iput handler and you don't have
to look at it at all. :)
-Kees
--
Kees Cook
