From: Kaixin Wang kxwang23@m.fudan.edu.cn

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=...

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[ 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 kxwang23@m.fudan.edu.cn Signed-off-by: Helge Deller deller@gmx.de Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Lin Yujun linyujun809@huawei.com --- 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 d59c8a59f582..fe0cb57447de 100644 --- a/drivers/video/fbdev/pxafb.c +++ b/drivers/video/fbdev/pxafb.c @@ -2437,6 +2437,7 @@ 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);