High · published February 26, 2025
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 ("fbdev: 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.