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| author | Eric Dumazet <edumazet@google.com> | 2018-03-14 18:53:00 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-03-17 17:03:45 -0400 |
| commit | cce6294cc2eaa083482e1d85d8db5845c82a7e14 (patch) | |
| tree | a067ed90ac97c73c1ab5d924a3dbef9906cbcc13 /net/sched | |
| parent | 7b7ef57c0dd2bb367ad41a77e5136c5579ae4026 (diff) | |
| download | linux-cce6294cc2eaa083482e1d85d8db5845c82a7e14.tar.bz2 | |
net: sched: fix uses after free
syzbot reported one use-after-free in pfifo_fast_enqueue() [1]
Issue here is that we can not reuse skb after a successful skb_array_produce()
since another cpu might have consumed it already.
I believe a similar problem exists in try_bulk_dequeue_skb_slow()
in case we put an skb into qdisc_enqueue_skb_bad_txq() for lockless qdisc.
[1]
BUG: KASAN: use-after-free in qdisc_pkt_len include/net/sch_generic.h:610 [inline]
BUG: KASAN: use-after-free in qdisc_qstats_cpu_backlog_inc include/net/sch_generic.h:712 [inline]
BUG: KASAN: use-after-free in pfifo_fast_enqueue+0x4bc/0x5e0 net/sched/sch_generic.c:639
Read of size 4 at addr ffff8801cede37e8 by task syzkaller717588/5543
CPU: 1 PID: 5543 Comm: syzkaller717588 Not tainted 4.16.0-rc4+ #265
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x24d lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report+0x23c/0x360 mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
qdisc_pkt_len include/net/sch_generic.h:610 [inline]
qdisc_qstats_cpu_backlog_inc include/net/sch_generic.h:712 [inline]
pfifo_fast_enqueue+0x4bc/0x5e0 net/sched/sch_generic.c:639
__dev_xmit_skb net/core/dev.c:3216 [inline]
Fixes: c5ad119fb6c0 ("net: sched: pfifo_fast use skb_array")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot+ed43b6903ab968b16f54@syzkaller.appspotmail.com
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
| -rw-r--r-- | net/sched/sch_generic.c | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 190570f21b20..7e3fbe9cc936 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -106,6 +106,14 @@ static inline void qdisc_enqueue_skb_bad_txq(struct Qdisc *q, __skb_queue_tail(&q->skb_bad_txq, skb); + if (qdisc_is_percpu_stats(q)) { + qdisc_qstats_cpu_backlog_inc(q, skb); + qdisc_qstats_cpu_qlen_inc(q); + } else { + qdisc_qstats_backlog_inc(q, skb); + q->q.qlen++; + } + if (lock) spin_unlock(lock); } @@ -196,14 +204,6 @@ static void try_bulk_dequeue_skb_slow(struct Qdisc *q, break; if (unlikely(skb_get_queue_mapping(nskb) != mapping)) { qdisc_enqueue_skb_bad_txq(q, nskb); - - if (qdisc_is_percpu_stats(q)) { - qdisc_qstats_cpu_backlog_inc(q, nskb); - qdisc_qstats_cpu_qlen_inc(q); - } else { - qdisc_qstats_backlog_inc(q, nskb); - q->q.qlen++; - } break; } skb->next = nskb; @@ -628,6 +628,7 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, int band = prio2band[skb->priority & TC_PRIO_MAX]; struct pfifo_fast_priv *priv = qdisc_priv(qdisc); struct skb_array *q = band2list(priv, band); + unsigned int pkt_len = qdisc_pkt_len(skb); int err; err = skb_array_produce(q, skb); @@ -636,7 +637,10 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, return qdisc_drop_cpu(skb, qdisc, to_free); qdisc_qstats_cpu_qlen_inc(qdisc); - qdisc_qstats_cpu_backlog_inc(qdisc, skb); + /* Note: skb can not be used after skb_array_produce(), + * so we better not use qdisc_qstats_cpu_backlog_inc() + */ + this_cpu_add(qdisc->cpu_qstats->backlog, pkt_len); return NET_XMIT_SUCCESS; } |