CVE-2022-49419 Information

Description

In the Linux kernel the following vulnerability has been resolved:

video: fbdev: vesafb: Fix a use-after-free due early fb_info cleanup

Commit b3c9a924aab6 (bdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove) fixed a use-after-free error due the vesafb driver freeing the fb_info in the .remove handler instead of doing it in .fb_destroy.

This can happen if the .fb_destroy callback is executed after the .remove callback since the former tries to access a pointer freed by the latter.

But that change didn’t take into account that another possible scenario is that .fb_destroy is called before the .remove callback. For example if no process has the fbdev chardev opened by the time the driver is removed.

If that’s the case fb_info will be freed when unregister_framebuffer() is called making the fb_info pointer accessed in vesafb_remove() after that to no longer be valid.

To prevent that move the expression containing the info->par to happen before the unregister_framebuffer() function call.

Reference

https://git.kernel.org/stable/c/0fac5f8fb1bc2fc4f8714bf5e743c9cc3f547c63 https://git.kernel.org/stable/c/acde4003efc16480375543638484d8f13f2e99a3 https://git.kernel.org/stable/c/d260cad015945d1f4bb9b028a096f648506106a2 https://git.kernel.org/stable/c/f605f5558ecc175ec70016a3c15f007cb6386531