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authorDaniel Borkmann <daniel@iogearbox.net>2018-01-16 01:12:09 +0300
committerDavid S. Miller <davem@davemloft.net>2018-01-16 23:02:36 +0300
commit81d947e2b8dd2394586c3eaffdd2357797d3bf59 (patch)
treeb2c2471dc85467003cb0918a08652b7235f23746 /net/sched/sch_api.c
parent70eeff66c4696cee4076d6388b6bede5bd7ff71c (diff)
downloadlinux-81d947e2b8dd2394586c3eaffdd2357797d3bf59.tar.xz
net, sched: fix panic when updating miniq {b,q}stats
While working on fixing another bug, I ran into the following panic on arm64 by simply attaching clsact qdisc, adding a filter and running traffic on ingress to it: [...] [ 178.188591] Unable to handle kernel read from unreadable memory at virtual address 810fb501f000 [ 178.197314] Mem abort info: [ 178.200121] ESR = 0x96000004 [ 178.203168] Exception class = DABT (current EL), IL = 32 bits [ 178.209095] SET = 0, FnV = 0 [ 178.212157] EA = 0, S1PTW = 0 [ 178.215288] Data abort info: [ 178.218175] ISV = 0, ISS = 0x00000004 [ 178.222019] CM = 0, WnR = 0 [ 178.224997] user pgtable: 4k pages, 48-bit VAs, pgd = 0000000023cb3f33 [ 178.231531] [0000810fb501f000] *pgd=0000000000000000 [ 178.236508] Internal error: Oops: 96000004 [#1] SMP [...] [ 178.311855] CPU: 73 PID: 2497 Comm: ping Tainted: G W 4.15.0-rc7+ #5 [ 178.319413] Hardware name: FOXCONN R2-1221R-A4/C2U4N_MB, BIOS G31FB18A 03/31/2017 [ 178.326887] pstate: 60400005 (nZCv daif +PAN -UAO) [ 178.331685] pc : __netif_receive_skb_core+0x49c/0xac8 [ 178.336728] lr : __netif_receive_skb+0x28/0x78 [ 178.341161] sp : ffff00002344b750 [ 178.344465] x29: ffff00002344b750 x28: ffff810fbdfd0580 [ 178.349769] x27: 0000000000000000 x26: ffff000009378000 [...] [ 178.418715] x1 : 0000000000000054 x0 : 0000000000000000 [ 178.424020] Process ping (pid: 2497, stack limit = 0x000000009f0a3ff4) [ 178.430537] Call trace: [ 178.432976] __netif_receive_skb_core+0x49c/0xac8 [ 178.437670] __netif_receive_skb+0x28/0x78 [ 178.441757] process_backlog+0x9c/0x160 [ 178.445584] net_rx_action+0x2f8/0x3f0 [...] Reason is that sch_ingress and sch_clsact are doing mini_qdisc_pair_init() which sets up miniq pointers to cpu_{b,q}stats from the underlying qdisc. Problem is that this cannot work since they are actually set up right after the qdisc ->init() callback in qdisc_create(), so first packet going into sch_handle_ingress() tries to call mini_qdisc_bstats_cpu_update() and we therefore panic. In order to fix this, allocation of {b,q}stats needs to happen before we call into ->init(). In net-next, there's already such option through commit d59f5ffa59d8 ("net: sched: a dflt qdisc may be used with per cpu stats"). However, the bug needs to be fixed in net still for 4.15. Thus, include these bits to reduce any merge churn and reuse the static_flags field to set TCQ_F_CPUSTATS, and remove the allocation from qdisc_create() since there is no other user left. Prashant Bhole ran into the same issue but for net-next, thus adding him below as well as co-author. Same issue was also reported by Sandipan Das when using bcc. Fixes: 46209401f8f6 ("net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath") Reference: https://lists.iovisor.org/pipermail/iovisor-dev/2018-January/001190.html Reported-by: Sandipan Das <sandipan@linux.vnet.ibm.com> Co-authored-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp> Co-authored-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jiri Pirko <jiri@resnulli.us> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_api.c')
-rw-r--r--net/sched/sch_api.c15
1 files changed, 1 insertions, 14 deletions
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 0f1eab99ff4e..52529b7f8d96 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1063,17 +1063,6 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
}
if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS])) == 0) {
- if (qdisc_is_percpu_stats(sch)) {
- sch->cpu_bstats =
- netdev_alloc_pcpu_stats(struct gnet_stats_basic_cpu);
- if (!sch->cpu_bstats)
- goto err_out4;
-
- sch->cpu_qstats = alloc_percpu(struct gnet_stats_queue);
- if (!sch->cpu_qstats)
- goto err_out4;
- }
-
if (tca[TCA_STAB]) {
stab = qdisc_get_stab(tca[TCA_STAB]);
if (IS_ERR(stab)) {
@@ -1115,7 +1104,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
ops->destroy(sch);
err_out3:
dev_put(dev);
- kfree((char *) sch - sch->padded);
+ qdisc_free(sch);
err_out2:
module_put(ops->owner);
err_out:
@@ -1123,8 +1112,6 @@ err_out:
return NULL;
err_out4:
- free_percpu(sch->cpu_bstats);
- free_percpu(sch->cpu_qstats);
/*
* Any broken qdiscs that would require a ops->reset() here?
* The qdisc was never in action so it shouldn't be necessary.