lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 28 Sep 2022 12:46:10 +0300 From: Leon Romanovsky <leon@...nel.org> To: Duoming Zhou <duoming@....edu.cn> Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, isdn@...ux-pingi.de, kuba@...nel.org Subject: Re: [PATCH V2] mISDN: fix use-after-free bugs in l1oip timer handlers On Fri, Sep 23, 2022 at 10:25:14PM +0800, Duoming Zhou wrote: > The l1oip_cleanup() traverses the l1oip_ilist and calls > release_card() to cleanup module and stack. However, > release_card() calls del_timer() to delete the timers > such as keep_tl and timeout_tl. If the timer handler is > running, the del_timer() will not stop it and result in > UAF bugs. One of the processes is shown below: > > (cleanup routine) | (timer handler) > release_card() | l1oip_timeout() > ... | > del_timer() | ... > ... | > kfree(hc) //FREE | > | hc->timeout_on = 0 //USE > > Fix by calling del_timer_sync() in release_card(), which > makes sure the timer handlers have finished before the > resources, such as l1oip and so on, have been deallocated. > > What's more, the hc->workq and hc->socket_thread can kick > those timers right back in. We use del_timer_sync(&hc->keep_tl) > and cancel_work_sync(&hc->keep_tl) twice to stop keep_tl timer > and hc->workq. Then, we add del_timer_sync(&hc->timeout_tl) > behind l1oip_socket_close() to stop timeout_tl timer. > > Fixes: 3712b42d4b1b ("Add layer1 over IP support") > Signed-off-by: Duoming Zhou <duoming@....edu.cn> > --- > Changes in v2: > - Solve the problem that timers could be restarted by other threads. > > drivers/isdn/mISDN/l1oip_core.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/drivers/isdn/mISDN/l1oip_core.c b/drivers/isdn/mISDN/l1oip_core.c > index 2c40412466e..7b89d98a781 100644 > --- a/drivers/isdn/mISDN/l1oip_core.c > +++ b/drivers/isdn/mISDN/l1oip_core.c > @@ -1232,17 +1232,16 @@ release_card(struct l1oip *hc) > { > int ch; > > - if (timer_pending(&hc->keep_tl)) > - del_timer(&hc->keep_tl); > - > - if (timer_pending(&hc->timeout_tl)) > - del_timer(&hc->timeout_tl); > - > + del_timer_sync(&hc->keep_tl); > + cancel_work_sync(&hc->workq); > + del_timer_sync(&hc->keep_tl); > cancel_work_sync(&hc->workq); It is racy, the call twice to del_timer_sync and cancel_work_sync doesn't solve "the problem that timers could be restarted by other threads." Thanks > > if (hc->socket_thread) > l1oip_socket_close(hc); > > + del_timer_sync(&hc->timeout_tl); > + > if (hc->registered && hc->chan[hc->d_idx].dch) > mISDN_unregister_device(&hc->chan[hc->d_idx].dch->dev); > for (ch = 0; ch < 128; ch++) { > -- > 2.17.1 >
Powered by blists - more mailing lists