| Message ID | 20241105094823.2403806-1-dmantipov@yandex.ru (mailing list archive) |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] can: fix skb reference counting in j1939_session_new() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Series ignored based on subject |
Tue, Nov 05, 2024 at 10:48:23AM CET, dmantipov@yandex.ru wrote: >Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each >new skb, I assume that the same should be done for an initial one It is odd to write "I assume" for fix like this. You should know for sure, don't you? >in 'j1939_session_new()' just to avoid refcount underflow. > >Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com >Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 >Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") >Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> >--- >v2: resend after hitting skb refcount underflow once again when looking >around https://syzkaller.appspot.com/bug?extid=0e6ddb1ef80986bdfe64 >--- > net/can/j1939/transport.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c >index 319f47df3330..95f7a7e65a73 100644 >--- a/net/can/j1939/transport.c >+++ b/net/can/j1939/transport.c >@@ -1505,7 +1505,7 @@ static struct j1939_session *j1939_session_new(struct j1939_priv *priv, > session->state = J1939_SESSION_NEW; > > skb_queue_head_init(&session->skb_queue); >- skb_queue_tail(&session->skb_queue, skb); >+ skb_queue_tail(&session->skb_queue, skb_get(skb)); > > skcb = j1939_skb_to_cb(skb); > memcpy(&session->skcb, skcb, sizeof(session->skcb)); >-- >2.47.0 > >
On Tue, Nov 05, 2024 at 05:37:53PM +0100, Jiri Pirko wrote: > Tue, Nov 05, 2024 at 10:48:23AM CET, dmantipov@yandex.ru wrote: > >Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each > >new skb, I assume that the same should be done for an initial one > > It is odd to write "I assume" for fix like this. You should know for > sure, don't you? Hm... looks the there is more then one refcounting problem at this point. skb_queue is set from 3 different paths, with resulting 3 different refcount states: j1939_sk_send_loop() skb = j1939_sk_alloc_skb() // skb with refcount == 1 if (!session) { session = j1939_tp_send(priv, skb, size) ... session = j1939_session_new(priv, skb, size); skb_queue_tail(&session->skb_queue, skb); // skb refcount == 1 } else { j1939_session_skb_queue(session, skb); // here, skb is refcounted skb_queue_tail(&session->skb_queue, skb_get(skb)); // skb refcount == 2 } // at the end of function, skb refcount == 1 or 2 j1939_xtp_rx_rts_session_new() j1939_session_fresh_new() skb = alloc_skb() // skb with refcount == 1 session = j1939_session_new(priv, skb, size); skb_queue_tail(&session->skb_queue, skb); skb_put(skb, size); // skb with refcount == 0 I agree with this patch, but there is missing skb_put() in j1939_sk_send_loop() > > >in 'j1939_session_new()' just to avoid refcount underflow. > > > >Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com > >Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 > >Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > >Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > >--- > >v2: resend after hitting skb refcount underflow once again when looking > >around https://syzkaller.appspot.com/bug?extid=0e6ddb1ef80986bdfe64 > >--- > > net/can/j1939/transport.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > >diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c > >index 319f47df3330..95f7a7e65a73 100644 > >--- a/net/can/j1939/transport.c > >+++ b/net/can/j1939/transport.c > >@@ -1505,7 +1505,7 @@ static struct j1939_session *j1939_session_new(struct j1939_priv *priv, > > session->state = J1939_SESSION_NEW; > > > > skb_queue_head_init(&session->skb_queue); > >- skb_queue_tail(&session->skb_queue, skb); > >+ skb_queue_tail(&session->skb_queue, skb_get(skb)); > > > > skcb = j1939_skb_to_cb(skb); > > memcpy(&session->skcb, skcb, sizeof(session->skcb)); > >-- > >2.47.0 > > > > >
On 11/5/24 7:37 PM, Jiri Pirko wrote: > It is odd to write "I assume" for fix like this. You should know for > sure, don't you? Well, the final vote is up to the maintainer(s). Dmitry
On 11/6/24 12:43 PM, Oleksij Rempel wrote: > Hm... looks the there is more then one refcounting problem at this > point. skb_queue is set from 3 different paths, with resulting 3 different > refcount states: I'll take a look; anyway I would prefer "one patch per one problem" approach. Dmitry
Wed, Nov 06, 2024 at 12:03:57PM CET, dmantipov@yandex.ru wrote: >On 11/5/24 7:37 PM, Jiri Pirko wrote: > >> It is odd to write "I assume" for fix like this. You should know for >> sure, don't you? > >Well, the final vote is up to the maintainer(s). Vote of what? > >Dmitry >
On Tue, Nov 05, 2024 at 12:48:23PM +0300, Dmitry Antipov wrote: > Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each > new skb, I assume that the same should be done for an initial one > in 'j1939_session_new()' just to avoid refcount underflow. > > Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
On 29.11.2024 13:55:56, Oleksij Rempel wrote: > On Tue, Nov 05, 2024 at 12:48:23PM +0300, Dmitry Antipov wrote: > > Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each > > new skb, I assume that the same should be done for an initial one > > in 'j1939_session_new()' just to avoid refcount underflow. > > > > Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 > > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > > Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> > Acked-by: Oleksij Rempel <o.rempel@pengutronix.de> Can you re-phrase the commit message. The "assume" is not appropriate :) Thanks, Marc
On 29.11.2024 13:59:28, Marc Kleine-Budde wrote: > On 29.11.2024 13:55:56, Oleksij Rempel wrote: > > On Tue, Nov 05, 2024 at 12:48:23PM +0300, Dmitry Antipov wrote: > > > Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each > > > new skb, I assume that the same should be done for an initial one > > > in 'j1939_session_new()' just to avoid refcount underflow. > > > > > > Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com > > > Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 > > > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > > > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > > > > Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> > > Acked-by: Oleksij Rempel <o.rempel@pengutronix.de> > > Can you re-phrase the commit message. The "assume" is not appropriate :) What about: Since j1939_session_skb_queue() does an extra skb_get() for each new skb, do the same for the initial one in j1939_session_new() to avoid refcount underflow. regards, Marc
On Fri, Nov 29, 2024 at 02:05:11PM +0100, Marc Kleine-Budde wrote: > On 29.11.2024 13:59:28, Marc Kleine-Budde wrote: > > On 29.11.2024 13:55:56, Oleksij Rempel wrote: > > > On Tue, Nov 05, 2024 at 12:48:23PM +0300, Dmitry Antipov wrote: > > > > Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each > > > > new skb, I assume that the same should be done for an initial one > > > > in 'j1939_session_new()' just to avoid refcount underflow. > > > > > > > > Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com > > > > Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 > > > > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > > > > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > > > > > > Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> > > > Acked-by: Oleksij Rempel <o.rempel@pengutronix.de> > > > > Can you re-phrase the commit message. The "assume" is not appropriate :) > > What about: > > Since j1939_session_skb_queue() does an extra skb_get() for each new > skb, do the same for the initial one in j1939_session_new() to avoid > refcount underflow. Sounds good. Thx!
On Wed, Nov 06, 2024 at 10:43:04AM +0100, Oleksij Rempel wrote: > On Tue, Nov 05, 2024 at 05:37:53PM +0100, Jiri Pirko wrote: > > Tue, Nov 05, 2024 at 10:48:23AM CET, dmantipov@yandex.ru wrote: > > >Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each > > >new skb, I assume that the same should be done for an initial one > > > > It is odd to write "I assume" for fix like this. You should know for > > sure, don't you? > > Hm... looks the there is more then one refcounting problem at this > point. skb_queue is set from 3 different paths, with resulting 3 different > refcount states: > > j1939_sk_send_loop() > skb = j1939_sk_alloc_skb() // skb with refcount == 1 > if (!session) { > session = j1939_tp_send(priv, skb, size) > ... > session = j1939_session_new(priv, skb, size); > skb_queue_tail(&session->skb_queue, skb); // skb refcount == 1 > > } else { > j1939_session_skb_queue(session, skb); > // here, skb is refcounted > skb_queue_tail(&session->skb_queue, skb_get(skb)); // skb refcount == 2 > } > > // at the end of function, skb refcount == 1 or 2 > > j1939_xtp_rx_rts_session_new() > j1939_session_fresh_new() > skb = alloc_skb() // skb with refcount == 1 > session = j1939_session_new(priv, skb, size); > skb_queue_tail(&session->skb_queue, skb); > skb_put(skb, size); // skb with refcount == 0 > > I agree with this patch, but there is missing skb_put() in j1939_sk_send_loop() Please forget it, no skb_free is needed in the j1939_sk_send_loop(). Regards, Oleksij
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index 319f47df3330..95f7a7e65a73 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -1505,7 +1505,7 @@ static struct j1939_session *j1939_session_new(struct j1939_priv *priv, session->state = J1939_SESSION_NEW; skb_queue_head_init(&session->skb_queue); - skb_queue_tail(&session->skb_queue, skb); + skb_queue_tail(&session->skb_queue, skb_get(skb)); skcb = j1939_skb_to_cb(skb); memcpy(&session->skcb, skcb, sizeof(session->skcb));
Since 'j1939_session_skb_queue()' do an extra 'skb_get()' for each new skb, I assume that the same should be done for an initial one in 'j1939_session_new()' just to avoid refcount underflow. Reported-by: syzbot+d4e8dc385d9258220c31@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31 Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> --- v2: resend after hitting skb refcount underflow once again when looking around https://syzkaller.appspot.com/bug?extid=0e6ddb1ef80986bdfe64 --- net/can/j1939/transport.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)