CVE-2021-47533 Information

Description

In the Linux kernel the following vulnerability has been resolved:

drm/vc4: kms: Clear the HVS FIFO commit pointer once done

Commit 9ec03d7f1ed3 (\drm/vc4: kms: Wait on previous FIFO users before a commit) introduced a wait on the previous commit done on a given HVS FIFO.

However we never cleared that pointer once done. Since drm_crtc_commit_put can free the drm_crtc_commit structure directly if we were the last user this means that it can lead to a use-after free if we were to duplicate the state and that stale pointer would even be copied to the new state.

Set the pointer to NULL once we’re done with the wait so that we don’t carry over a pointer to a free’d structure.

Reference

https://git.kernel.org/stable/c/2931db9a5ed219546cf2ae0546698faf78281b89 https://git.kernel.org/stable/c/d134c5ff71c7f2320fc7997f2fbbdedf0c76889a