[PATCH 3.18 18/20] net: sched: fix panic in rate estimators

Greg Kroah-Hartman
2015-02-25T02:18:18Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 0d32ef8cef9aa8f375e128f78b77caceaa7e8da0 ]

Doing the following commands on a non idle network device
panics the box instantly, because cpu_bstats gets overwritten
by stats.

tc qdisc add dev eth0 root <your_favorite_qdisc>
... some traffic (one packet is enough) ...
tc qdisc replace dev eth0 root est 1sec 4sec <your_favorite_qdisc>

[ 325.355596] BUG: unable to handle kernel paging request at ffff8841dc5a074c
[ 325.362609] IP: [<ffffffff81541c9e>] __gnet_stats_copy_basic+0x3e/0x90
[ 325.369158] PGD 1fa7067 PUD 0
[ 325.372254] Oops: 0000 [#1] SMP
[ 325.375514] Modules linked in: ...
[ 325.398346] CPU: 13 PID: 14313 Comm: tc Not tainted 3.19.0-smp-DEV #1163
[ 325.412042] task: ffff8800793ab5d0 ti: ffff881ff2fa4000 task.ti: ffff881ff2fa4000
[ 325.419518] RIP: 0010:[<ffffffff81541c9e>] [<ffffffff81541c9e>] __gnet_stats_copy_basic+0x3e/0x90
[ 325.428506] RSP: 0018:ffff881ff2fa7928 EFLAGS: 00010286
[ 325.433824] RAX: 000000000000000c RBX: ffff881ff2fa796c RCX: 000000000000000c
[ 325.440988] RDX: ffff8841dc5a0744 RSI: 0000000000000060 RDI: 0000000000000060
[ 325.448120] RBP: ffff881ff2fa7948 R08: ffffffff81cd4f80 R09: 0000000000000000
[ 325.455268] R10: ffff883ff223e400 R11: 0000000000000000 R12: 000000015cba0744
[ 325.462405] R13: ffffffff81cd4f80 R14: ffff883ff223e460 R15: ffff883feea0722c
[ 325.469536] FS: 00007f2ee30fa700(0000) GS:ffff88407fa20000(0000) knlGS:0000000000000000
[ 325.477630] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 325.483380] CR2: ffff8841dc5a074c CR3: 0000003feeae9000 CR4: 00000000001407e0
[ 325.490510] Stack:
[ 325.492524] ffff883feea0722c ffff883fef719dc0 ffff883feea0722c ffff883ff223e4a0
[ 325.499990] ffff881ff2fa79a8 ffffffff815424ee ffff883ff223e49c 000000015cba0744
[ 325.507460] 00000000f2fa7978 0000000000000000 ffff881ff2fa79a8 ffff883ff223e4a0
[ 325.514956] Call Trace:
[ 325.517412] [<ffffffff815424ee>] gen_new_estimator+0x8e/0x230
[ 325.523250] [<ffffffff815427aa>] gen_replace_estimator+0x4a/0x60
[ 325.529349] [<ffffffff815718ab>] tc_modify_qdisc+0x52b/0x590
[ 325.535117] [<ffffffff8155edd0>] rtnetlink_rcv_msg+0xa0/0x240
[ 325.540963] [<ffffffff8155ed30>] ? __rtnl_unlock+0x20/0x20
[ 325.546532] [<ffffffff8157f811>] netlink_rcv_skb+0xb1/0xc0
[ 325.552145] [<ffffffff8155b355>] rtnetlink_rcv+0x25/0x40
[ 325.557558] [<ffffffff8157f0d8>] netlink_unicast+0x168/0x220
[ 325.563317] [<ffffffff8157f47c>] netlink_sendmsg+0x2ec/0x3e0

Lets play safe and not use an union : percpu 'pointers' are mostly read
anyway, and we have typically few qdiscs per host.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Fixes: 22e0f8b9322c ("net: sched: make bstats per cpu and estimator RCU safe")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/sch_generic.h | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -79,6 +79,9 @@ struct Qdisc {
struct netdev_queue *dev_queue;

struct gnet_stats_rate_est64 rate_est;
+ struct gnet_stats_basic_cpu __percpu *cpu_bstats;
+ struct gnet_stats_queue __percpu *cpu_qstats;
+
struct Qdisc *next_sched;
struct sk_buff *gso_skb;
/*
@@ -86,15 +89,9 @@ struct Qdisc {
*/
unsigned long state;
struct sk_buff_head q;
- union {
- struct gnet_stats_basic_packed bstats;
- struct gnet_stats_basic_cpu __percpu *cpu_bstats;
- } __packed;
+ struct gnet_stats_basic_packed bstats;
unsigned int __state;
- union {
- struct gnet_stats_queue qstats;
- struct gnet_stats_queue __percpu *cpu_qstats;
- } __packed;
+ struct gnet_stats_queue qstats;
struct rcu_head rcu_head;
int padded;
atomic_t refcnt;