Dne 26. 04. 21 v 16:23 Takashi Iwai napsal(a):
On Mon, 26 Apr 2021 15:11:29 +0200, Lv Yunlong wrote:
Our code analyzer reported a uaf.
In snd_emu8000_create_mixer, the callee snd_ctl_add(..,emu->controls[i]) calls snd_ctl_add_replace(.., kcontrol,..). Inside snd_ctl_add_replace(), if error happens, kcontrol will be freed by snd_ctl_free_one(kcontrol). Then emu->controls[i] points to a freed memory, and the execution comes to __error branch of snd_emu8000_create_mixer. The freed emu->controls[i] is used in snd_ctl_remove(card, emu->controls[i]).
My patch set emu->controls[i] to NULL if snd_ctl_add() failed to avoid the uaf.
Signed-off-by: Lv Yunlong lyl2019@mail.ustc.edu.cn
Thanks, applied now.
The bug was hard to be seen due to the coding style, so we'd need a cleanup, but it's a different story...
Yes, it would be better to assign the return value from snd_ctl_new1 to a local variable and set emu->controls[i] only when everything succeeds.
Jaroslav