| Message ID | 20211108180815.1822479-1-eric.dumazet@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 6dc25401cba4d428328eade8ceae717633fdd702 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] net/sched: sch_taprio: fix undefined behavior in ktime_mono_to_any | expand |
Hi Eric, Eric Dumazet <eric.dumazet@gmail.com> writes: > From: Eric Dumazet <edumazet@google.com> > > 1) if q->tk_offset == TK_OFFS_MAX, then get_tcp_tstamp() calls > ktime_mono_to_any() with out-of-bound value. > > 2) if q->tk_offset is changed in taprio_parse_clockid(), > taprio_get_time() might also call ktime_mono_to_any() > with out-of-bound value as sysbot found: > > UBSAN: array-index-out-of-bounds in kernel/time/timekeeping.c:908:27 > index 3 is out of range for type 'ktime_t *[3]' > CPU: 1 PID: 25668 Comm: kworker/u4:0 Not tainted 5.15.0-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > ubsan_epilogue+0xb/0x5a lib/ubsan.c:151 > __ubsan_handle_out_of_bounds.cold+0x62/0x6c lib/ubsan.c:291 > ktime_mono_to_any+0x1d4/0x1e0 kernel/time/timekeeping.c:908 > get_tcp_tstamp net/sched/sch_taprio.c:322 [inline] > get_packet_txtime net/sched/sch_taprio.c:353 [inline] > taprio_enqueue_one+0x5b0/0x1460 net/sched/sch_taprio.c:420 > taprio_enqueue+0x3b1/0x730 net/sched/sch_taprio.c:485 > dev_qdisc_enqueue+0x40/0x300 net/core/dev.c:3785 > __dev_xmit_skb net/core/dev.c:3869 [inline] > __dev_queue_xmit+0x1f6e/0x3630 net/core/dev.c:4194 > batadv_send_skb_packet+0x4a9/0x5f0 net/batman-adv/send.c:108 > batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:393 [inline] > batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:421 [inline] > batadv_iv_send_outstanding_bat_ogm_packet+0x6d7/0x8e0 net/batman-adv/bat_iv_ogm.c:1701 > process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 > worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 > kthread+0x405/0x4f0 kernel/kthread.c:327 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 > > Fixes: 7ede7b03484b ("taprio: make clock reference conversions easier") > Fixes: 54002066100b ("taprio: Adjust timestamps for TCP packets") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Cc: Vinicius Costa Gomes <vinicius.gomes@intel.com> > Cc: Vedang Patel <vedang.patel@intel.com> > Reported-by: syzbot <syzkaller@googlegroups.com> > --- I just tested this and it indeed fixes a crash when the user tries to configure the txtime-assisted mode using CLOCK_MONOTONIC. Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com> Cheers,
Hello: This patch was applied to netdev/net.git (master) by Jakub Kicinski <kuba@kernel.org>: On Mon, 8 Nov 2021 10:08:15 -0800 you wrote: > From: Eric Dumazet <edumazet@google.com> > > 1) if q->tk_offset == TK_OFFS_MAX, then get_tcp_tstamp() calls > ktime_mono_to_any() with out-of-bound value. > > 2) if q->tk_offset is changed in taprio_parse_clockid(), > taprio_get_time() might also call ktime_mono_to_any() > with out-of-bound value as sysbot found: > > [...] Here is the summary with links: - [net] net/sched: sch_taprio: fix undefined behavior in ktime_mono_to_any https://git.kernel.org/netdev/net/c/6dc25401cba4 You are awesome, thank you!
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index 9ab068fa2672be8febd227b96cbcf646bf51f661..377f896bdedc4575316c3bab1d661d9c88142ec0 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -95,18 +95,22 @@ static ktime_t sched_base_time(const struct sched_gate_list *sched) return ns_to_ktime(sched->base_time); } -static ktime_t taprio_get_time(struct taprio_sched *q) +static ktime_t taprio_mono_to_any(const struct taprio_sched *q, ktime_t mono) { - ktime_t mono = ktime_get(); + /* This pairs with WRITE_ONCE() in taprio_parse_clockid() */ + enum tk_offsets tk_offset = READ_ONCE(q->tk_offset); - switch (q->tk_offset) { + switch (tk_offset) { case TK_OFFS_MAX: return mono; default: - return ktime_mono_to_any(mono, q->tk_offset); + return ktime_mono_to_any(mono, tk_offset); } +} - return KTIME_MAX; +static ktime_t taprio_get_time(const struct taprio_sched *q) +{ + return taprio_mono_to_any(q, ktime_get()); } static void taprio_free_sched_cb(struct rcu_head *head) @@ -319,7 +323,7 @@ static ktime_t get_tcp_tstamp(struct taprio_sched *q, struct sk_buff *skb) return 0; } - return ktime_mono_to_any(skb->skb_mstamp_ns, q->tk_offset); + return taprio_mono_to_any(q, skb->skb_mstamp_ns); } /* There are a few scenarios where we will have to modify the txtime from @@ -1352,6 +1356,7 @@ static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb, } } else if (tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]) { int clockid = nla_get_s32(tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]); + enum tk_offsets tk_offset; /* We only support static clockids and we don't allow * for it to be modified after the first init. @@ -1366,22 +1371,24 @@ static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb, switch (clockid) { case CLOCK_REALTIME: - q->tk_offset = TK_OFFS_REAL; + tk_offset = TK_OFFS_REAL; break; case CLOCK_MONOTONIC: - q->tk_offset = TK_OFFS_MAX; + tk_offset = TK_OFFS_MAX; break; case CLOCK_BOOTTIME: - q->tk_offset = TK_OFFS_BOOT; + tk_offset = TK_OFFS_BOOT; break; case CLOCK_TAI: - q->tk_offset = TK_OFFS_TAI; + tk_offset = TK_OFFS_TAI; break; default: NL_SET_ERR_MSG(extack, "Invalid 'clockid'"); err = -EINVAL; goto out; } + /* This pairs with READ_ONCE() in taprio_mono_to_any */ + WRITE_ONCE(q->tk_offset, tk_offset); q->clockid = clockid; } else {