Commit 8fb91c35 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'inet-frags-avoid-possible-races-at-netns-dismantle' 



Eric Dumazet says:

====================
inet: frags: avoid possible races at netns dismantle

This patch series fixes a race happening on netns dismantle with
frag queues. While rhashtable_free_and_destroy() is running,
concurrent timers might run inet_frag_kill() and attempt
rhashtable_remove_fast() calls. This is not allowed by
rhashtable logic.

Since I do not want to add expensive synchronize_rcu() calls
in the netns dismantle path, I had to no longer inline
netns_frags structures, but dynamically allocate them.

The ten first patches make this preparation, so that
the last patch clearly shows the fix.

As this patch series is not exactly trivial, I chose to
target 5.3. We will backport it once soaked a bit.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents ddf6ddb0 3c8fc878

include/net/inet_frag.h

+34 −14
Original line number Diff line number Diff line
@@ -4,18 +4,22 @@ 


#include <linux/rhashtable-types.h>



struct netns_frags {

/* Per netns frag queues directory */

struct fqdir {

	/* sysctls */

	long			high_thresh;

	long			low_thresh;

	int			timeout;

	int			max_dist;

	struct inet_frags	*f;

	struct net		*net;

	bool			dead;



	struct rhashtable       rhashtable ____cacheline_aligned_in_smp;



	/* Keep atomic mem on separate cachelines in structs that include it */

	atomic_long_t		mem ____cacheline_aligned_in_smp;

	struct rcu_work		destroy_rwork;

};



/**
@@ -24,11 +28,13 @@ struct netns_frags { 
 * @INET_FRAG_FIRST_IN: first fragment has arrived

 * @INET_FRAG_LAST_IN: final fragment has arrived

 * @INET_FRAG_COMPLETE: frag queue has been processed and is due for destruction

 * @INET_FRAG_HASH_DEAD: inet_frag_kill() has not removed fq from rhashtable

 */

enum {

	INET_FRAG_FIRST_IN	= BIT(0),

	INET_FRAG_LAST_IN	= BIT(1),

	INET_FRAG_COMPLETE	= BIT(2),

	INET_FRAG_HASH_DEAD	= BIT(3),

};



struct frag_v4_compare_key {
@@ -64,7 +70,7 @@ struct frag_v6_compare_key { 
 * @meat: length of received fragments so far

 * @flags: fragment queue flags

 * @max_size: maximum received fragment size

 * @net: namespace that this frag belongs to

 * @fqdir: pointer to struct fqdir

 * @rcu: rcu head for freeing deferall

 */

struct inet_frag_queue {
@@ -84,7 +90,7 @@ struct inet_frag_queue { 
	int			meat;

	__u8			flags;

	u16			max_size;

	struct netns_frags      *net;

	struct fqdir		*fqdir;

	struct rcu_head		rcu;

};
@@ -103,16 +109,30 @@ struct inet_frags { 
int inet_frags_init(struct inet_frags *);

void inet_frags_fini(struct inet_frags *);



static inline int inet_frags_init_net(struct netns_frags *nf)

static inline int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f,

			     struct net *net)

{

	atomic_long_set(&nf->mem, 0);

	return rhashtable_init(&nf->rhashtable, &nf->f->rhash_params);

	struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL);

	int res;



	if (!fqdir)

		return -ENOMEM;

	fqdir->f = f;

	fqdir->net = net;

	res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params);

	if (res < 0) {

		kfree(fqdir);

		return res;

	}

void inet_frags_exit_net(struct netns_frags *nf);

	*fqdirp = fqdir;

	return 0;

}



void fqdir_exit(struct fqdir *fqdir);



void inet_frag_kill(struct inet_frag_queue *q);

void inet_frag_destroy(struct inet_frag_queue *q);

struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, void *key);

struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key);



/* Free all skbs in the queue; return the sum of their truesizes. */

unsigned int inet_frag_rbtree_purge(struct rb_root *root);
@@ -125,19 +145,19 @@ static inline void inet_frag_put(struct inet_frag_queue *q) 


/* Memory Tracking Functions. */



static inline long frag_mem_limit(const struct netns_frags *nf)

static inline long frag_mem_limit(const struct fqdir *fqdir)

{

	return atomic_long_read(&nf->mem);

	return atomic_long_read(&fqdir->mem);

}



static inline void sub_frag_mem_limit(struct netns_frags *nf, long val)

static inline void sub_frag_mem_limit(struct fqdir *fqdir, long val)

{

	atomic_long_sub(val, &nf->mem);

	atomic_long_sub(val, &fqdir->mem);

}



static inline void add_frag_mem_limit(struct netns_frags *nf, long val)

static inline void add_frag_mem_limit(struct fqdir *fqdir, long val)

{

	atomic_long_add(val, &nf->mem);

	atomic_long_add(val, &fqdir->mem);

}



/* RFC 3168 support :

include/net/netns/ieee802154_6lowpan.h

+1 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ struct netns_sysctl_lowpan { 


struct netns_ieee802154_lowpan {

	struct netns_sysctl_lowpan sysctl;

	struct netns_frags	frags;

	struct fqdir		*fqdir;

};



#endif

include/net/netns/ipv4.h

+1 −1
Original line number Diff line number Diff line
@@ -72,7 +72,7 @@ struct netns_ipv4 { 


	struct inet_peer_base	*peers;

	struct sock  * __percpu	*tcp_sk;

	struct netns_frags	frags;

	struct fqdir		*fqdir;

#ifdef CONFIG_NETFILTER

	struct xt_table		*iptable_filter;

	struct xt_table		*iptable_mangle;

include/net/netns/ipv6.h

+2 −2
Original line number Diff line number Diff line
@@ -58,7 +58,7 @@ struct netns_ipv6 { 
	struct ipv6_devconf	*devconf_all;

	struct ipv6_devconf	*devconf_dflt;

	struct inet_peer_base	*peers;

	struct netns_frags	frags;

	struct fqdir		*fqdir;

#ifdef CONFIG_NETFILTER

	struct xt_table		*ip6table_filter;

	struct xt_table		*ip6table_mangle;
@@ -116,7 +116,7 @@ struct netns_ipv6 { 


#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)

struct netns_nf_frag {

	struct netns_frags	frags;

	struct fqdir	*fqdir;

};

#endif

net/ieee802154/6lowpan/reassembly.c

+16 −20
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ fq_find(struct net *net, const struct lowpan_802154_cb *cb, 
	key.src = *src;

	key.dst = *dst;



	q = inet_frag_find(&ieee802154_lowpan->frags, &key);

	q = inet_frag_find(ieee802154_lowpan->fqdir, &key);

	if (!q)

		return NULL;
@@ -139,7 +139,7 @@ static int lowpan_frag_queue(struct lowpan_frag_queue *fq, 
		fq->q.flags |= INET_FRAG_FIRST_IN;



	fq->q.meat += skb->len;

	add_frag_mem_limit(fq->q.net, skb->truesize);

	add_frag_mem_limit(fq->q.fqdir, skb->truesize);



	if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&

	    fq->q.meat == fq->q.len) {
@@ -326,23 +326,18 @@ err: 
static struct ctl_table lowpan_frags_ns_ctl_table[] = {

	{

		.procname	= "6lowpanfrag_high_thresh",

		.data		= &init_net.ieee802154_lowpan.frags.high_thresh,

		.maxlen		= sizeof(unsigned long),

		.mode		= 0644,

		.proc_handler	= proc_doulongvec_minmax,

		.extra1		= &init_net.ieee802154_lowpan.frags.low_thresh

	},

	{

		.procname	= "6lowpanfrag_low_thresh",

		.data		= &init_net.ieee802154_lowpan.frags.low_thresh,

		.maxlen		= sizeof(unsigned long),

		.mode		= 0644,

		.proc_handler	= proc_doulongvec_minmax,

		.extra2		= &init_net.ieee802154_lowpan.frags.high_thresh

	},

	{

		.procname	= "6lowpanfrag_time",

		.data		= &init_net.ieee802154_lowpan.frags.timeout,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_jiffies,
@@ -377,17 +372,17 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net) 
		if (table == NULL)

			goto err_alloc;



		table[0].data = &ieee802154_lowpan->frags.high_thresh;

		table[0].extra1 = &ieee802154_lowpan->frags.low_thresh;

		table[1].data = &ieee802154_lowpan->frags.low_thresh;

		table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;

		table[2].data = &ieee802154_lowpan->frags.timeout;



		/* Don't export sysctls to unprivileged users */

		if (net->user_ns != &init_user_ns)

			table[0].procname = NULL;

	}



	table[0].data	= &ieee802154_lowpan->fqdir->high_thresh;

	table[0].extra1	= &ieee802154_lowpan->fqdir->low_thresh;

	table[1].data	= &ieee802154_lowpan->fqdir->low_thresh;

	table[1].extra2	= &ieee802154_lowpan->fqdir->high_thresh;

	table[2].data	= &ieee802154_lowpan->fqdir->timeout;



	hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);

	if (hdr == NULL)

		goto err_reg;
@@ -454,17 +449,18 @@ static int __net_init lowpan_frags_init_net(struct net *net) 
		net_ieee802154_lowpan(net);

	int res;



	ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;

	ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;

	ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;

	ieee802154_lowpan->frags.f = &lowpan_frags;



	res = inet_frags_init_net(&ieee802154_lowpan->frags);

	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);

	if (res < 0)

		return res;



	ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;

	ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;

	ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;



	res = lowpan_frags_ns_sysctl_register(net);

	if (res < 0)

		inet_frags_exit_net(&ieee802154_lowpan->frags);

		fqdir_exit(ieee802154_lowpan->fqdir);

	return res;

}
@@ -474,7 +470,7 @@ static void __net_exit lowpan_frags_exit_net(struct net *net) 
		net_ieee802154_lowpan(net);



	lowpan_frags_ns_sysctl_unregister(net);

	inet_frags_exit_net(&ieee802154_lowpan->frags);

	fqdir_exit(ieee802154_lowpan->fqdir);

}



static struct pernet_operations lowpan_frags_ops = {

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