From: Oleksij Rempel o.rempel@pengutronix.de
mainline inclusion from mainline-v5.13-rc7 commit 2030043e616cab40f510299f09b636285e0a3678 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4CE CVE: CVE-2021-47232
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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This patch fixes a Use-after-Free found by the syzbot.
The problem is that a skb is taken from the per-session skb queue, without incrementing the ref count. This leads to a Use-after-Free if the skb is taken concurrently from the session queue due to a CTS.
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") Link: https://lore.kernel.org/r/20210521115720.7533-1-o.rempel@pengutronix.de Cc: Hillf Danton hdanton@sina.com Cc: linux-stable stable@vger.kernel.org Reported-by: syzbot+220c1a29987a9a490903@syzkaller.appspotmail.com Reported-by: syzbot+45199c1b73b4013525cf@syzkaller.appspotmail.com Signed-off-by: Oleksij Rempel o.rempel@pengutronix.de Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Zhang Changzhong zhangchangzhong@huawei.com --- net/can/j1939/transport.c | 54 +++++++++++++++++++++++++++++++++++------------ 1 file changed, 40 insertions(+), 14 deletions(-)
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index 566fcf9..1a68b00 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -330,6 +330,9 @@ static void j1939_session_skb_drop_old(struct j1939_session *session)
if ((do_skcb->offset + do_skb->len) < offset_start) { __skb_unlink(do_skb, &session->skb_queue); + /* drop ref taken in j1939_session_skb_queue() */ + skb_unref(do_skb); + kfree_skb(do_skb); } spin_unlock_irqrestore(&session->skb_queue.lock, flags); @@ -349,12 +352,13 @@ void j1939_session_skb_queue(struct j1939_session *session,
skcb->flags |= J1939_ECU_LOCAL_SRC;
+ skb_get(skb); skb_queue_tail(&session->skb_queue, skb); }
static struct -sk_buff *j1939_session_skb_find_by_offset(struct j1939_session *session, - unsigned int offset_start) +sk_buff *j1939_session_skb_get_by_offset(struct j1939_session *session, + unsigned int offset_start) { struct j1939_priv *priv = session->priv; struct j1939_sk_buff_cb *do_skcb; @@ -371,6 +375,10 @@ sk_buff *j1939_session_skb_find_by_offset(struct j1939_session *session, skb = do_skb; } } + + if (skb) + skb_get(skb); + spin_unlock_irqrestore(&session->skb_queue.lock, flags);
if (!skb) @@ -381,12 +389,12 @@ sk_buff *j1939_session_skb_find_by_offset(struct j1939_session *session, return skb; }
-static struct sk_buff *j1939_session_skb_find(struct j1939_session *session) +static struct sk_buff *j1939_session_skb_get(struct j1939_session *session) { unsigned int offset_start;
offset_start = session->pkt.dpo * 7; - return j1939_session_skb_find_by_offset(session, offset_start); + return j1939_session_skb_get_by_offset(session, offset_start); }
/* see if we are receiver @@ -773,7 +781,7 @@ static int j1939_session_tx_dat(struct j1939_session *session) int ret = 0; u8 dat[8];
- se_skb = j1939_session_skb_find_by_offset(session, session->pkt.tx * 7); + se_skb = j1939_session_skb_get_by_offset(session, session->pkt.tx * 7); if (!se_skb) return -ENOBUFS;
@@ -798,7 +806,8 @@ static int j1939_session_tx_dat(struct j1939_session *session) netdev_err_once(priv->ndev, "%s: 0x%p: requested data outside of queued buffer: offset %i, len %i, pkt.tx: %i\n", __func__, session, skcb->offset, se_skb->len , session->pkt.tx); - return -EOVERFLOW; + ret = -EOVERFLOW; + goto out_free; }
if (!len) { @@ -832,6 +841,12 @@ static int j1939_session_tx_dat(struct j1939_session *session) if (pkt_done) j1939_tp_set_rxtimeout(session, 250);
+ out_free: + if (ret) + kfree_skb(se_skb); + else + consume_skb(se_skb); + return ret; }
@@ -1004,7 +1019,7 @@ static int j1939_xtp_txnext_receiver(struct j1939_session *session) static int j1939_simple_txnext(struct j1939_session *session) { struct j1939_priv *priv = session->priv; - struct sk_buff *se_skb = j1939_session_skb_find(session); + struct sk_buff *se_skb = j1939_session_skb_get(session); struct sk_buff *skb; int ret;
@@ -1012,8 +1027,10 @@ static int j1939_simple_txnext(struct j1939_session *session) return 0;
skb = skb_clone(se_skb, GFP_ATOMIC); - if (!skb) - return -ENOMEM; + if (!skb) { + ret = -ENOMEM; + goto out_free; + }
can_skb_set_owner(skb, se_skb->sk);
@@ -1021,12 +1038,18 @@ static int j1939_simple_txnext(struct j1939_session *session)
ret = j1939_send_one(priv, skb); if (ret) - return ret; + goto out_free;
j1939_sk_errqueue(session, J1939_ERRQUEUE_SCHED); j1939_sk_queue_activate_next(session);
- return 0; + out_free: + if (ret) + kfree_skb(se_skb); + else + consume_skb(se_skb); + + return ret; }
static bool j1939_session_deactivate_locked(struct j1939_session *session) @@ -1167,9 +1190,10 @@ static void j1939_session_completed(struct j1939_session *session) struct sk_buff *skb;
if (!session->transmission) { - skb = j1939_session_skb_find(session); + skb = j1939_session_skb_get(session); /* distribute among j1939 receivers */ j1939_sk_recv(session->priv, skb); + consume_skb(skb); }
j1939_session_deactivate_activate_next(session); @@ -1732,7 +1756,7 @@ static void j1939_xtp_rx_dat_one(struct j1939_session *session, { struct j1939_priv *priv = session->priv; struct j1939_sk_buff_cb *skcb; - struct sk_buff *se_skb; + struct sk_buff *se_skb = NULL; const u8 *dat; u8 *tpdat; int offset; @@ -1773,7 +1797,7 @@ static void j1939_xtp_rx_dat_one(struct j1939_session *session, goto out_session_cancel; }
- se_skb = j1939_session_skb_find_by_offset(session, packet * 7); + se_skb = j1939_session_skb_get_by_offset(session, packet * 7); if (!se_skb) { netdev_warn(priv->ndev, "%s: 0x%p: no skb found\n", __func__, session); @@ -1816,11 +1840,13 @@ static void j1939_xtp_rx_dat_one(struct j1939_session *session, j1939_tp_set_rxtimeout(session, 250); } session->last_cmd = 0xff; + consume_skb(se_skb); j1939_session_put(session);
return;
out_session_cancel: + kfree_skb(se_skb); j1939_session_timers_cancel(session); j1939_session_cancel(session, J1939_XTP_ABORT_FAULT); j1939_session_put(session);