Thanks Greg.
We definitely want to backport this fix to all relevant kernels, I
will work on these backports soon.
Thanks.
On Wed, Nov 6, 2019 at 7:42 AM <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
>
> The patch below does not apply to the 4.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From 55667441c84fa5e0911a0aac44fb059c15ba6da2 Mon Sep 17 00:00:00 2001
> From: Eric Dumazet <edumazet@xxxxxxxxxx>
> Date: Tue, 22 Oct 2019 07:57:46 -0700
> Subject: [PATCH] net/flow_dissector: switch to siphash
>
> UDP IPv6 packets auto flowlabels are using a 32bit secret
> (static u32 hashrnd in net/core/flow_dissector.c) and
> apply jhash() over fields known by the receivers.
>
> Attackers can easily infer the 32bit secret and use this information
> to identify a device and/or user, since this 32bit secret is only
> set at boot time.
>
> Really, using jhash() to generate cookies sent on the wire
> is a serious security concern.
>
> Trying to change the rol32(hash, 16) in ip6_make_flowlabel() would be
> a dead end. Trying to periodically change the secret (like in sch_sfq.c)
> could change paths taken in the network for long lived flows.
>
> Let's switch to siphash, as we did in commit df453700e8d8
> ("inet: switch IP ID generator to siphash")
>
> Using a cryptographically strong pseudo random function will solve this
> privacy issue and more generally remove other weak points in the stack.
>
> Packet schedulers using skb_get_hash_perturb() benefit from this change.
>
> Fixes: b56774163f99 ("ipv6: Enable auto flow labels by default")
> Fixes: 42240901f7c4 ("ipv6: Implement different admin modes for automatic flow labels")
> Fixes: 67800f9b1f4e ("ipv6: Call skb_get_hash_flowi6 to get skb->hash in ip6_make_flowlabel")
> Fixes: cb1ce2ef387b ("ipv6: Implement automatic flow label generation on transmit")
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Reported-by: Jonathan Berger <jonathann1@xxxxxxxxx>
> Reported-by: Amit Klein <aksecurity@xxxxxxxxx>
> Reported-by: Benny Pinkas <benny@xxxxxxxxxx>
> Cc: Tom Herbert <tom@xxxxxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 7914fdaf4226..a391147c03d4 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1354,7 +1354,8 @@ static inline __u32 skb_get_hash_flowi6(struct sk_buff *skb, const struct flowi6
> return skb->hash;
> }
>
> -__u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb);
> +__u32 skb_get_hash_perturb(const struct sk_buff *skb,
> + const siphash_key_t *perturb);
>
> static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
> {
> diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
> index 90bd210be060..5cd12276ae21 100644
> --- a/include/net/flow_dissector.h
> +++ b/include/net/flow_dissector.h
> @@ -4,6 +4,7 @@
>
> #include <linux/types.h>
> #include <linux/in6.h>
> +#include <linux/siphash.h>
> #include <uapi/linux/if_ether.h>
>
> /**
> @@ -276,7 +277,7 @@ struct flow_keys_basic {
> struct flow_keys {
> struct flow_dissector_key_control control;
> #define FLOW_KEYS_HASH_START_FIELD basic
> - struct flow_dissector_key_basic basic;
> + struct flow_dissector_key_basic basic __aligned(SIPHASH_ALIGNMENT);
> struct flow_dissector_key_tags tags;
> struct flow_dissector_key_vlan vlan;
> struct flow_dissector_key_vlan cvlan;
> diff --git a/include/net/fq.h b/include/net/fq.h
> index d126b5d20261..2ad85e683041 100644
> --- a/include/net/fq.h
> +++ b/include/net/fq.h
> @@ -69,7 +69,7 @@ struct fq {
> struct list_head backlogs;
> spinlock_t lock;
> u32 flows_cnt;
> - u32 perturbation;
> + siphash_key_t perturbation;
> u32 limit;
> u32 memory_limit;
> u32 memory_usage;
> diff --git a/include/net/fq_impl.h b/include/net/fq_impl.h
> index be40a4b327e3..107c0d700ed6 100644
> --- a/include/net/fq_impl.h
> +++ b/include/net/fq_impl.h
> @@ -108,7 +108,7 @@ static struct sk_buff *fq_tin_dequeue(struct fq *fq,
>
> static u32 fq_flow_idx(struct fq *fq, struct sk_buff *skb)
> {
> - u32 hash = skb_get_hash_perturb(skb, fq->perturbation);
> + u32 hash = skb_get_hash_perturb(skb, &fq->perturbation);
>
> return reciprocal_scale(hash, fq->flows_cnt);
> }
> @@ -308,7 +308,7 @@ static int fq_init(struct fq *fq, int flows_cnt)
> INIT_LIST_HEAD(&fq->backlogs);
> spin_lock_init(&fq->lock);
> fq->flows_cnt = max_t(u32, flows_cnt, 1);
> - fq->perturbation = prandom_u32();
> + get_random_bytes(&fq->perturbation, sizeof(fq->perturbation));
> fq->quantum = 300;
> fq->limit = 8192;
> fq->memory_limit = 16 << 20; /* 16 MBytes */
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 7c09d87d3269..68eda10d0680 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -1350,30 +1350,21 @@ bool __skb_flow_dissect(const struct net *net,
> }
> EXPORT_SYMBOL(__skb_flow_dissect);
>
> -static u32 hashrnd __read_mostly;
> +static siphash_key_t hashrnd __read_mostly;
> static __always_inline void __flow_hash_secret_init(void)
> {
> net_get_random_once(&hashrnd, sizeof(hashrnd));
> }
>
> -static __always_inline u32 __flow_hash_words(const u32 *words, u32 length,
> - u32 keyval)
> +static const void *flow_keys_hash_start(const struct flow_keys *flow)
> {
> - return jhash2(words, length, keyval);
> -}
> -
> -static inline const u32 *flow_keys_hash_start(const struct flow_keys *flow)
> -{
> - const void *p = flow;
> -
> - BUILD_BUG_ON(FLOW_KEYS_HASH_OFFSET % sizeof(u32));
> - return (const u32 *)(p + FLOW_KEYS_HASH_OFFSET);
> + BUILD_BUG_ON(FLOW_KEYS_HASH_OFFSET % SIPHASH_ALIGNMENT);
> + return &flow->FLOW_KEYS_HASH_START_FIELD;
> }
>
> static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
> {
> size_t diff = FLOW_KEYS_HASH_OFFSET + sizeof(flow->addrs);
> - BUILD_BUG_ON((sizeof(*flow) - FLOW_KEYS_HASH_OFFSET) % sizeof(u32));
> BUILD_BUG_ON(offsetof(typeof(*flow), addrs) !=
> sizeof(*flow) - sizeof(flow->addrs));
>
> @@ -1388,7 +1379,7 @@ static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
> diff -= sizeof(flow->addrs.tipckey);
> break;
> }
> - return (sizeof(*flow) - diff) / sizeof(u32);
> + return sizeof(*flow) - diff;
> }
>
> __be32 flow_get_u32_src(const struct flow_keys *flow)
> @@ -1454,14 +1445,15 @@ static inline void __flow_hash_consistentify(struct flow_keys *keys)
> }
> }
>
> -static inline u32 __flow_hash_from_keys(struct flow_keys *keys, u32 keyval)
> +static inline u32 __flow_hash_from_keys(struct flow_keys *keys,
> + const siphash_key_t *keyval)
> {
> u32 hash;
>
> __flow_hash_consistentify(keys);
>
> - hash = __flow_hash_words(flow_keys_hash_start(keys),
> - flow_keys_hash_length(keys), keyval);
> + hash = siphash(flow_keys_hash_start(keys),
> + flow_keys_hash_length(keys), keyval);
> if (!hash)
> hash = 1;
>
> @@ -1471,12 +1463,13 @@ static inline u32 __flow_hash_from_keys(struct flow_keys *keys, u32 keyval)
> u32 flow_hash_from_keys(struct flow_keys *keys)
> {
> __flow_hash_secret_init();
> - return __flow_hash_from_keys(keys, hashrnd);
> + return __flow_hash_from_keys(keys, &hashrnd);
> }
> EXPORT_SYMBOL(flow_hash_from_keys);
>
> static inline u32 ___skb_get_hash(const struct sk_buff *skb,
> - struct flow_keys *keys, u32 keyval)
> + struct flow_keys *keys,
> + const siphash_key_t *keyval)
> {
> skb_flow_dissect_flow_keys(skb, keys,
> FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
> @@ -1524,7 +1517,7 @@ u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
> &keys, NULL, 0, 0, 0,
> FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
>
> - return __flow_hash_from_keys(&keys, hashrnd);
> + return __flow_hash_from_keys(&keys, &hashrnd);
> }
> EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric);
>
> @@ -1544,13 +1537,14 @@ void __skb_get_hash(struct sk_buff *skb)
>
> __flow_hash_secret_init();
>
> - hash = ___skb_get_hash(skb, &keys, hashrnd);
> + hash = ___skb_get_hash(skb, &keys, &hashrnd);
>
> __skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
> }
> EXPORT_SYMBOL(__skb_get_hash);
>
> -__u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb)
> +__u32 skb_get_hash_perturb(const struct sk_buff *skb,
> + const siphash_key_t *perturb)
> {
> struct flow_keys keys;
>
> diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
> index 23cd1c873a2c..be35f03b657b 100644
> --- a/net/sched/sch_hhf.c
> +++ b/net/sched/sch_hhf.c
> @@ -5,11 +5,11 @@
> * Copyright (C) 2013 Nandita Dukkipati <nanditad@xxxxxxxxxx>
> */
>
> -#include <linux/jhash.h>
> #include <linux/jiffies.h>
> #include <linux/module.h>
> #include <linux/skbuff.h>
> #include <linux/vmalloc.h>
> +#include <linux/siphash.h>
> #include <net/pkt_sched.h>
> #include <net/sock.h>
>
> @@ -126,7 +126,7 @@ struct wdrr_bucket {
>
> struct hhf_sched_data {
> struct wdrr_bucket buckets[WDRR_BUCKET_CNT];
> - u32 perturbation; /* hash perturbation */
> + siphash_key_t perturbation; /* hash perturbation */
> u32 quantum; /* psched_mtu(qdisc_dev(sch)); */
> u32 drop_overlimit; /* number of times max qdisc packet
> * limit was hit
> @@ -264,7 +264,7 @@ static enum wdrr_bucket_idx hhf_classify(struct sk_buff *skb, struct Qdisc *sch)
> }
>
> /* Get hashed flow-id of the skb. */
> - hash = skb_get_hash_perturb(skb, q->perturbation);
> + hash = skb_get_hash_perturb(skb, &q->perturbation);
>
> /* Check if this packet belongs to an already established HH flow. */
> flow_pos = hash & HHF_BIT_MASK;
> @@ -582,7 +582,7 @@ static int hhf_init(struct Qdisc *sch, struct nlattr *opt,
>
> sch->limit = 1000;
> q->quantum = psched_mtu(qdisc_dev(sch));
> - q->perturbation = prandom_u32();
> + get_random_bytes(&q->perturbation, sizeof(q->perturbation));
> INIT_LIST_HEAD(&q->new_buckets);
> INIT_LIST_HEAD(&q->old_buckets);
>
> diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
> index d448fe3068e5..4074c50ac3d7 100644
> --- a/net/sched/sch_sfb.c
> +++ b/net/sched/sch_sfb.c
> @@ -18,7 +18,7 @@
> #include <linux/errno.h>
> #include <linux/skbuff.h>
> #include <linux/random.h>
> -#include <linux/jhash.h>
> +#include <linux/siphash.h>
> #include <net/ip.h>
> #include <net/pkt_sched.h>
> #include <net/pkt_cls.h>
> @@ -45,7 +45,7 @@ struct sfb_bucket {
> * (Section 4.4 of SFB reference : moving hash functions)
> */
> struct sfb_bins {
> - u32 perturbation; /* jhash perturbation */
> + siphash_key_t perturbation; /* siphash key */
> struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
> };
>
> @@ -217,7 +217,8 @@ static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_da
>
> static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
> {
> - q->bins[slot].perturbation = prandom_u32();
> + get_random_bytes(&q->bins[slot].perturbation,
> + sizeof(q->bins[slot].perturbation));
> }
>
> static void sfb_swap_slot(struct sfb_sched_data *q)
> @@ -314,9 +315,9 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
> /* If using external classifiers, get result and record it. */
> if (!sfb_classify(skb, fl, &ret, &salt))
> goto other_drop;
> - sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
> + sfbhash = siphash_1u32(salt, &q->bins[slot].perturbation);
> } else {
> - sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation);
> + sfbhash = skb_get_hash_perturb(skb, &q->bins[slot].perturbation);
> }
>
>
> @@ -352,7 +353,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
> /* Inelastic flow */
> if (q->double_buffering) {
> sfbhash = skb_get_hash_perturb(skb,
> - q->bins[slot].perturbation);
> + &q->bins[slot].perturbation);
> if (!sfbhash)
> sfbhash = 1;
> sfb_skb_cb(skb)->hashes[slot] = sfbhash;
> diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
> index 68404a9d2ce4..c787d4d46017 100644
> --- a/net/sched/sch_sfq.c
> +++ b/net/sched/sch_sfq.c
> @@ -14,7 +14,7 @@
> #include <linux/errno.h>
> #include <linux/init.h>
> #include <linux/skbuff.h>
> -#include <linux/jhash.h>
> +#include <linux/siphash.h>
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> #include <net/netlink.h>
> @@ -117,7 +117,7 @@ struct sfq_sched_data {
> u8 headdrop;
> u8 maxdepth; /* limit of packets per flow */
>
> - u32 perturbation;
> + siphash_key_t perturbation;
> u8 cur_depth; /* depth of longest slot */
> u8 flags;
> unsigned short scaled_quantum; /* SFQ_ALLOT_SIZE(quantum) */
> @@ -157,7 +157,7 @@ static inline struct sfq_head *sfq_dep_head(struct sfq_sched_data *q, sfq_index
> static unsigned int sfq_hash(const struct sfq_sched_data *q,
> const struct sk_buff *skb)
> {
> - return skb_get_hash_perturb(skb, q->perturbation) & (q->divisor - 1);
> + return skb_get_hash_perturb(skb, &q->perturbation) & (q->divisor - 1);
> }
>
> static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
> @@ -607,9 +607,11 @@ static void sfq_perturbation(struct timer_list *t)
> struct sfq_sched_data *q = from_timer(q, t, perturb_timer);
> struct Qdisc *sch = q->sch;
> spinlock_t *root_lock = qdisc_lock(qdisc_root_sleeping(sch));
> + siphash_key_t nkey;
>
> + get_random_bytes(&nkey, sizeof(nkey));
> spin_lock(root_lock);
> - q->perturbation = prandom_u32();
> + q->perturbation = nkey;
> if (!q->filter_list && q->tail)
> sfq_rehash(sch);
> spin_unlock(root_lock);
> @@ -688,7 +690,7 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
> del_timer(&q->perturb_timer);
> if (q->perturb_period) {
> mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
> - q->perturbation = prandom_u32();
> + get_random_bytes(&q->perturbation, sizeof(q->perturbation));
> }
> sch_tree_unlock(sch);
> kfree(p);
> @@ -745,7 +747,7 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt,
> q->quantum = psched_mtu(qdisc_dev(sch));
> q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
> q->perturb_period = 0;
> - q->perturbation = prandom_u32();
> + get_random_bytes(&q->perturbation, sizeof(q->perturbation));
>
> if (opt) {
> int err = sfq_change(sch, opt);
>
