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Miller" , Sasha Levin Subject: [PATCH 4.19 087/229] mISDN: fix use-after-free bugs in l1oip timer handlers Date: Mon, 24 Oct 2022 13:30:06 +0200 Message-Id: <20221024113001.873325181@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024112959.085534368@linuxfoundation.org> References: <20221024112959.085534368@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Duoming Zhou [ Upstream commit 2568a7e0832ee30b0a351016d03062ab4e0e0a3f ] 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 =3D 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 add a bool flag to show if card is released. Then, check this flag in hc->workq and hc->socket_thread. Fixes: 3712b42d4b1b ("Add layer1 over IP support") Signed-off-by: Duoming Zhou Reviewed-by: Leon Romanovsky Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/isdn/mISDN/l1oip.h | 1 + drivers/isdn/mISDN/l1oip_core.c | 13 +++++++------ 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/isdn/mISDN/l1oip.h b/drivers/isdn/mISDN/l1oip.h index 7ea10db20e3a..48133d022812 100644 --- a/drivers/isdn/mISDN/l1oip.h +++ b/drivers/isdn/mISDN/l1oip.h @@ -59,6 +59,7 @@ struct l1oip { int bundle; /* bundle channels in one frm */ int codec; /* codec to use for transmis. */ int limit; /* limit number of bchannels */ + bool shutdown; /* if card is released */ =20 /* timer */ struct timer_list keep_tl; diff --git a/drivers/isdn/mISDN/l1oip_core.c b/drivers/isdn/mISDN/l1oip_cor= e.c index b05022f94f18..2f4a01ab25e8 100644 --- a/drivers/isdn/mISDN/l1oip_core.c +++ b/drivers/isdn/mISDN/l1oip_core.c @@ -289,7 +289,7 @@ l1oip_socket_send(struct l1oip *hc, u8 localcodec, u8 c= hannel, u32 chanmask, p =3D frame; =20 /* restart timer */ - if (time_before(hc->keep_tl.expires, jiffies + 5 * HZ)) + if (time_before(hc->keep_tl.expires, jiffies + 5 * HZ) && !hc->shutdown) mod_timer(&hc->keep_tl, jiffies + L1OIP_KEEPALIVE * HZ); else hc->keep_tl.expires =3D jiffies + L1OIP_KEEPALIVE * HZ; @@ -615,7 +615,9 @@ l1oip_socket_parse(struct l1oip *hc, struct sockaddr_in= *sin, u8 *buf, int len) goto multiframe; =20 /* restart timer */ - if (time_before(hc->timeout_tl.expires, jiffies + 5 * HZ) || !hc->timeout= _on) { + if ((time_before(hc->timeout_tl.expires, jiffies + 5 * HZ) || + !hc->timeout_on) && + !hc->shutdown) { hc->timeout_on =3D 1; mod_timer(&hc->timeout_tl, jiffies + L1OIP_TIMEOUT * HZ); } else /* only adjust timer */ @@ -1247,11 +1249,10 @@ release_card(struct l1oip *hc) { int ch; =20 - if (timer_pending(&hc->keep_tl)) - del_timer(&hc->keep_tl); + hc->shutdown =3D true; =20 - if (timer_pending(&hc->timeout_tl)) - del_timer(&hc->timeout_tl); + del_timer_sync(&hc->keep_tl); + del_timer_sync(&hc->timeout_tl); =20 cancel_work_sync(&hc->workq); =20 --=20 2.35.1