On Fri, Nov 23, 2018 at 04:51:49PM -0800, Viacheslav Dubeyko wrote:
> On Fri, 2018-11-23 at 17:04 +0800, Pan Bian wrote:
> > The function hfs_bmap_free frees node via hfs_bnode_put(node).
> > However,
> > it then reads node->this when dumping error message on an error path,
> > which may result in a use-after-free bug. This patch frees node only
> > when it is never used.
> >
> > Fixes: d614267329f("hfs/hfsplus: convert printks to pr_<level>")
> >
> > Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
> > ---
> > fs/hfs/btree.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
> > index 98b96ff..19017d2 100644
> > --- a/fs/hfs/btree.c
> > +++ b/fs/hfs/btree.c
> > @@ -338,13 +338,14 @@ void hfs_bmap_free(struct hfs_bnode *node)
> >
> > nidx -= len * 8;
> > i = node->next;
> > - hfs_bnode_put(node);
> > if (!i) {
> > /* panic */;
> > pr_crit("unable to free bnode %u. bmap not
> > found!\n",
> > node->this);
>
>
> What's about simply to store node->this into the local variable in the
> beginning of the cycle? In this case, it is possible to use the node ID
> in the pr_crit() and to use the hfs_bnode_put(node) in the same place
> without to use it twice. What do you think?
Of course, it is a solution. But I think doing like that does not really
simplify the code, as we have to declare an extra local variable, and
assign node->this to it...
Best,
Pan
>
> Thanks,
> Vyacheslav Dubeyko.
>
>
> > + hfs_bnode_put(node);
> > return;
> > }
> > + hfs_bnode_put(node);
> > node = hfs_bnode_find(tree, i);
> > if (IS_ERR(node))
> > return;
