At 2024-09-12 01:38:26, "Helge Deller" <deller@xxxxxx> wrote: >On 9/11/24 16:29, Kaixin Wang wrote: >> 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@xxxxxxxxxxxxxx> >> --- >> drivers/video/fbdev/pxafb.c | 1 + >> 1 file changed, 1 insertion(+) > >I've added the patch to the fbdev git tree, but changed the title to: >"fbdev: pxafb: Fix possible use after free in pxafb_task()" > >Thanks! >Helge > > Thanks for the review! I appreciate the adjustment to the patch title to make it more precise. Best regards, Kaixin Wang
