From 7e1da9481fe9e83df031336eb9e2a7a554608b72 Mon Sep 17 00:00:00 2001 From: Kaixin Wang Date: Wed, 30 Oct 2024 15:45:11 +0800 Subject: [PATCH] fbdev: pxafb: Fix possible use after free in pxafb_task() stable inclusion from stable-v6.6.55 commit fdda354f60a576d52dcf90351254714681df4370 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRCT CVE: CVE-2024-49924 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fdda354f60a576d52dcf90351254714681df4370 --------------------------- [ Upstream commit 4a6921095eb04a900e0000da83d9475eb958e61e ] 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 Signed-off-by: Sasha Levin Signed-off-by: Lin Yujun --- 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 f1551e00eb12..a0db2b3d0736 100644 --- a/drivers/video/fbdev/pxafb.c +++ b/drivers/video/fbdev/pxafb.c @@ -2408,6 +2408,7 @@ static int 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); -- Gitee