diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-08-24 21:12:28 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-08-24 21:28:24 -0700 |
| commit | 551143d8d954fe398324a5caa276f518466c428b (patch) | |
| tree | 8f6df2cbbc63eac473ae6588b05a0b1800874481 /net/sched | |
| parent | c2062ee3d9615828109ffe8089fbf69bed394d05 (diff) | |
net_sched: fix a refcount_t issue with noop_qdisc
syzkaller reported a refcount_t warning [1]
Issue here is that noop_qdisc refcnt was never really considered as
a true refcount, since qdisc_destroy() found TCQ_F_BUILTIN set :
if (qdisc->flags & TCQ_F_BUILTIN ||
!refcount_dec_and_test(&qdisc->refcnt)))
return;
Meaning that all atomic_inc() we did on noop_qdisc.refcnt were not
really needed, but harmless until refcount_t came.
To fix this problem, we simply need to not increment noop_qdisc.refcnt,
since we never decrement it.
[1]
refcount_t: increment on 0; use-after-free.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 21754 at lib/refcount.c:152 refcount_inc+0x47/0x50 lib/refcount.c:152
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 21754 Comm: syz-executor7 Not tainted 4.13.0-rc6+ #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:52
panic+0x1e4/0x417 kernel/panic.c:180
__warn+0x1c4/0x1d9 kernel/panic.c:541
report_bug+0x211/0x2d0 lib/bug.c:183
fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:190
do_trap_no_signal arch/x86/kernel/traps.c:224 [inline]
do_trap+0x260/0x390 arch/x86/kernel/traps.c:273
do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:310
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:323
invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:846
RIP: 0010:refcount_inc+0x47/0x50 lib/refcount.c:152
RSP: 0018:ffff8801c43477a0 EFLAGS: 00010282
RAX: 000000000000002b RBX: ffffffff86093c14 RCX: 0000000000000000
RDX: 000000000000002b RSI: ffffffff8159314e RDI: ffffed0038868ee8
RBP: ffff8801c43477a8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff86093ac0
R13: 0000000000000001 R14: ffff8801d0f3bac0 R15: dffffc0000000000
attach_default_qdiscs net/sched/sch_generic.c:792 [inline]
dev_activate+0x7d3/0xaa0 net/sched/sch_generic.c:833
__dev_open+0x227/0x330 net/core/dev.c:1380
__dev_change_flags+0x695/0x990 net/core/dev.c:6726
dev_change_flags+0x88/0x140 net/core/dev.c:6792
dev_ifsioc+0x5a6/0x930 net/core/dev_ioctl.c:256
dev_ioctl+0x2bc/0xf90 net/core/dev_ioctl.c:554
sock_do_ioctl+0x94/0xb0 net/socket.c:968
sock_ioctl+0x2c2/0x440 net/socket.c:1058
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
Fixes: 7b9364050246 ("net, sched: convert Qdisc.refcnt from atomic_t to refcount_t")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Reshetova, Elena <elena.reshetova@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
| -rw-r--r-- | net/sched/sch_api.c | 6 | ||||
| -rw-r--r-- | net/sched/sch_generic.c | 2 |
2 files changed, 4 insertions, 4 deletions
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index a3fa144b8648..4fb5a3222d0d 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -836,7 +836,7 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent, old = dev_graft_qdisc(dev_queue, new); if (new && i > 0) - refcount_inc(&new->refcnt); + qdisc_refcount_inc(new); if (!ingress) qdisc_destroy(old); @@ -847,7 +847,7 @@ skip: notify_and_destroy(net, skb, n, classid, dev->qdisc, new); if (new && !new->ops->attach) - refcount_inc(&new->refcnt); + qdisc_refcount_inc(new); dev->qdisc = new ? : &noop_qdisc; if (new && new->ops->attach) @@ -1256,7 +1256,7 @@ replay: if (q == p || (p && check_loop(q, p, 0))) return -ELOOP; - refcount_inc(&q->refcnt); + qdisc_refcount_inc(q); goto graft; } else { if (!q) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 57ba406f1437..4ba6da5fb254 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -785,7 +785,7 @@ static void attach_default_qdiscs(struct net_device *dev) dev->priv_flags & IFF_NO_QUEUE) { netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL); dev->qdisc = txq->qdisc_sleeping; - refcount_inc(&dev->qdisc->refcnt); + qdisc_refcount_inc(dev->qdisc); } else { qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT); if (qdisc) { |