[OpenWrt-Devel] [PATCH libubox 9/9] avl: guard against theoretical null pointer dereference

Yousong Zhou yszhou4tech at gmail.com
Wed Nov 20 08:46:17 EST 2019


On Wed, 20 Nov 2019 at 21:33, Petr Štetiar <ynezz at true.cz> wrote:
>
> Yousong Zhou <yszhou4tech at gmail.com> [2019-11-20 20:33:06]:
>
> Hi,
>
> thanks for review!
>
> > The first check (node->left == NULL && node->right == NULL) if
> > matched, will return.
>
> You can see the code path leading to null pointer dereference for yourself[1].
> I wish, that analyzer could output test case directly :-) I wanted to write
> test case myself in order to verify it, but it's quite time consuming so I
> rather decided to move on with this simple silencer.
>
> 1. https://ynezz.gitlab.io/-/openwrt-libubox/-/jobs/355230141/artifacts/build/scan/2019-11-19-163708-203-1/index.html

The graph is very impressive.  It requires the fiddler to first point
node->parent to a stranger whose left and right children are both not
node itself ;)  In that case, I prefer the program just segfault.  No
way it should continue or recover.

                yousong

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