From 4a6921095eb04a900e0000da83d9475eb958e61e Mon Sep 17 00:00:00 2001 From: Kaixin Wang Date: Wed, 11 Sep 2024 22:29:52 +0800 Subject: [PATCH] fbdev: pxafb: Fix possible use after free in pxafb_task() In the pxafb_probe function, it calls the pxafb_init_fbinfo function, after which &fbi->task is associated with pxafb_task. Moreover, within this pxafb_init_fbinfo function, the pxafb_blank function within the &pxafb_ops struct is capable of scheduling work. If we remove the module which will call pxafb_remove to make cleanup, it will call unregister_framebuffer function which can call do_unregister_framebuffer to free fbi->fb through put_fb_info(fb_info), while the work mentioned above will be used. The sequence of operations that may lead to a UAF bug is as follows: CPU0 CPU1 | pxafb_task pxafb_remove | unregister_framebuffer(info) | do_unregister_framebuffer(fb_info) | put_fb_info(fb_info) | // free fbi->fb | set_ctrlr_state(fbi, state) | __pxafb_lcd_power(fbi, 0) | fbi->lcd_power(on, &fbi->fb.var) | //use fbi->fb Fix it by ensuring that the work is canceled before proceeding with the cleanup in pxafb_remove. Note that only root user can remove the driver at runtime. Signed-off-by: Kaixin Wang Signed-off-by: Helge Deller --- drivers/video/fbdev/pxafb.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/video/fbdev/pxafb.c b/drivers/video/fbdev/pxafb.c index 2ef56fa28aff..5ce02495cda6 100644 --- a/drivers/video/fbdev/pxafb.c +++ b/drivers/video/fbdev/pxafb.c @@ -2403,6 +2403,7 @@ static void pxafb_remove(struct platform_device *dev) info = &fbi->fb; pxafb_overlay_exit(fbi); + cancel_work_sync(&fbi->task); unregister_framebuffer(info); pxafb_disable_controller(fbi);