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inet: frags: change inet_frag_kill() to defer refcount updates

Browse source 
In the following patch, we no longer assume inet_frag_kill()
callers own a reference.

Consuming two refcounts from inet_frag_kill() would lead in UAF.

Propagate the pointer to the refs that will be consumed later
by the final inet_frag_putn() call.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250312082250.1803501-4-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Eric Dumazet 2025-03-12 08:22:49 +00:00 • committed by Paolo Abeni
parent a2fb987c0e
commit eb0dfc0ef1
7 changed files with 53 additions and 49 deletions
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2
include/net/inet_frag.h
View file

@ -137,7 +137,7 @@ static inline void fqdir_pre_exit(struct fqdir *fqdir)
}
void fqdir_exit(struct fqdir *fqdir);
void inet_frag_kill(struct inet_frag_queue *q);
void inet_frag_kill(struct inet_frag_queue *q, int *refs);
void inet_frag_destroy(struct inet_frag_queue *q);
struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key);

2
include/net/ipv6_frag.h
View file

@ -78,7 +78,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
goto out;
fq->q.flags |= INET_FRAG_DROP;
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, &refs);
dev = dev_get_by_index_rcu(net, fq->iif);
if (!dev)

17
net/ieee802154/6lowpan/reassembly.c
View file

@ -31,7 +31,8 @@ static const char lowpan_frags_cache_name[] = "lowpan-frags";
static struct inet_frags lowpan_frags;
static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev, struct net_device *ldev);
struct sk_buff *prev, struct net_device *ldev,
int *refs);
static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
{
@ -54,7 +55,7 @@ static void lowpan_frag_expire(struct timer_list *t)
if (fq->q.flags & INET_FRAG_COMPLETE)
goto out;
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, &refs);
out:
spin_unlock(&fq->q.lock);
inet_frag_putn(&fq->q, refs);
@ -83,7 +84,8 @@ fq_find(struct net *net, const struct lowpan_802154_cb *cb,
}
static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
struct sk_buff *skb, u8 frag_type)
struct sk_buff *skb, u8 frag_type,
int *refs)
{
struct sk_buff *prev_tail;
struct net_device *ldev;
@ -144,7 +146,7 @@ static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
res = lowpan_frag_reasm(fq, skb, prev_tail, ldev);
res = lowpan_frag_reasm(fq, skb, prev_tail, ldev, refs);
skb->_skb_refdst = orefdst;
return res;
}
@ -163,11 +165,12 @@ err:
* the last and the first frames arrived and all the bits are here.
*/
static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *ldev)
struct sk_buff *prev_tail, struct net_device *ldev,
int *refs)
{
void *reasm_data;
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
if (!reasm_data)
@ -306,7 +309,7 @@ int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
int ret, refs = 1;
spin_lock(&fq->q.lock);
ret = lowpan_frag_queue(fq, skb, frag_type);
ret = lowpan_frag_queue(fq, skb, frag_type, &refs);
spin_unlock(&fq->q.lock);
inet_frag_putn(&fq->q, refs);

12
net/ipv4/inet_fragment.c
View file

@ -225,10 +225,10 @@ void fqdir_exit(struct fqdir *fqdir)
}
EXPORT_SYMBOL(fqdir_exit);
void inet_frag_kill(struct inet_frag_queue *fq)
void inet_frag_kill(struct inet_frag_queue *fq, int *refs)
{
if (del_timer(&fq->timer))
refcount_dec(&fq->refcnt);
(*refs)++;
if (!(fq->flags & INET_FRAG_COMPLETE)) {
struct fqdir *fqdir = fq->fqdir;
@ -243,7 +243,7 @@ void inet_frag_kill(struct inet_frag_queue *fq)
if (!READ_ONCE(fqdir->dead)) {
rhashtable_remove_fast(&fqdir->rhashtable, &fq->node,
fqdir->f->rhash_params);
refcount_dec(&fq->refcnt);
(*refs)++;
} else {
fq->flags |= INET_FRAG_HASH_DEAD;
}
@ -349,9 +349,11 @@ static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir,
*prev = rhashtable_lookup_get_insert_key(&fqdir->rhashtable, &q->key,
&q->node, f->rhash_params);
if (*prev) {
int refs = 2;
q->flags |= INET_FRAG_COMPLETE;
inet_frag_kill(q);
inet_frag_destroy(q);
inet_frag_kill(q, &refs);
inet_frag_putn(q, refs);
return NULL;
}
return q;

30
net/ipv4/ip_fragment.c
View file

@ -76,7 +76,8 @@ static u8 ip4_frag_ecn(u8 tos)
static struct inet_frags ip4_frags;
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev);
struct sk_buff *prev_tail, struct net_device *dev,
int *refs);
static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
@ -107,14 +108,6 @@ static void ip4_frag_free(struct inet_frag_queue *q)
inet_putpeer(qp->peer);
}
/* Kill ipq entry. It is not destroyed immediately,
* because caller (and someone more) holds reference count.
*/
static void ipq_kill(struct ipq *ipq)
{
inet_frag_kill(&ipq->q);
}
static bool frag_expire_skip_icmp(u32 user)
{
return user == IP_DEFRAG_AF_PACKET ||
@ -152,7 +145,7 @@ static void ip_expire(struct timer_list *t)
goto out;
qp->q.flags |= INET_FRAG_DROP;
ipq_kill(qp);
inet_frag_kill(&qp->q, &refs);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
@ -271,7 +264,7 @@ static int ip_frag_reinit(struct ipq *qp)
}
/* Add new segment to existing queue. */
static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb, int *refs)
{
struct net *net = qp->q.fqdir->net;
int ihl, end, flags, offset;
@ -291,7 +284,7 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
unlikely(ip_frag_too_far(qp)) &&
unlikely(err = ip_frag_reinit(qp))) {
ipq_kill(qp);
inet_frag_kill(&qp->q, refs);
goto err;
}
@ -375,10 +368,10 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
err = ip_frag_reasm(qp, skb, prev_tail, dev);
err = ip_frag_reasm(qp, skb, prev_tail, dev, refs);
skb->_skb_refdst = orefdst;
if (err)
inet_frag_kill(&qp->q);
inet_frag_kill(&qp->q, refs);
return err;
}
@ -395,7 +388,7 @@ insert_error:
err = -EINVAL;
__IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
discard_qp:
inet_frag_kill(&qp->q);
inet_frag_kill(&qp->q, refs);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
err:
kfree_skb_reason(skb, reason);
@ -409,7 +402,8 @@ static bool ip_frag_coalesce_ok(const struct ipq *qp)
/* Build a new IP datagram from all its fragments. */
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev)
struct sk_buff *prev_tail, struct net_device *dev,
int *refs)
{
struct net *net = qp->q.fqdir->net;
struct iphdr *iph;
@ -417,7 +411,7 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
int len, err;
u8 ecn;
ipq_kill(qp);
inet_frag_kill(&qp->q, refs);
ecn = ip_frag_ecn_table[qp->ecn];
if (unlikely(ecn == 0xff)) {
@ -495,7 +489,7 @@ int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
spin_lock(&qp->q.lock);
ret = ip_frag_queue(qp, skb);
ret = ip_frag_queue(qp, skb, &refs);
spin_unlock(&qp->q.lock);
inet_frag_putn(&qp->q, refs);

21
net/ipv6/netfilter/nf_conntrack_reasm.c
View file

@ -123,7 +123,8 @@ static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
#endif
static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev);
struct sk_buff *prev_tail, struct net_device *dev,
int *refs);
static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
{
@ -167,7 +168,8 @@ static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
const struct frag_hdr *fhdr, int nhoff)
const struct frag_hdr *fhdr, int nhoff,
int *refs)
{
unsigned int payload_len;
struct net_device *dev;
@ -221,7 +223,7 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
* this case. -DaveM
*/
pr_debug("end of fragment not rounded to 8 bytes.\n");
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
return -EPROTO;
}
if (end > fq->q.len) {
@ -287,7 +289,7 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
err = nf_ct_frag6_reasm(fq, skb, prev, dev);
err = nf_ct_frag6_reasm(fq, skb, prev, dev, refs);
skb->_skb_refdst = orefdst;
/* After queue has assumed skb ownership, only 0 or
@ -301,7 +303,7 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
return -EINPROGRESS;
insert_error:
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
err:
skb_dst_drop(skb);
return -EINVAL;
@ -315,13 +317,14 @@ err:
* the last and the first frames arrived and all the bits are here.
*/
static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev)
struct sk_buff *prev_tail, struct net_device *dev,
int *refs)
{
void *reasm_data;
int payload_len;
u8 ecn;
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
ecn = ip_frag_ecn_table[fq->ecn];
if (unlikely(ecn == 0xff))
@ -372,7 +375,7 @@ static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
return 0;
err:
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
return -EINVAL;
}
@ -483,7 +486,7 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
spin_lock_bh(&fq->q.lock);
ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff, &refs);
if (ret == -EPROTO) {
skb->transport_header = savethdr;
ret = 0;

18
net/ipv6/reassembly.c
View file

@ -68,7 +68,8 @@ static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
static struct inet_frags ip6_frags;
static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev);
struct sk_buff *prev_tail, struct net_device *dev,
int *refs);
static void ip6_frag_expire(struct timer_list *t)
{
@ -105,7 +106,7 @@ fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif)
static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
struct frag_hdr *fhdr, int nhoff,
u32 *prob_offset)
u32 *prob_offset, int *refs)
{
struct net *net = dev_net(skb_dst(skb)->dev);
int offset, end, fragsize;
@ -220,7 +221,7 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
err = ip6_frag_reasm(fq, skb, prev_tail, dev);
err = ip6_frag_reasm(fq, skb, prev_tail, dev, refs);
skb->_skb_refdst = orefdst;
return err;
}
@ -238,7 +239,7 @@ insert_error:
__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
IPSTATS_MIB_REASM_OVERLAPS);
discard_fq:
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
IPSTATS_MIB_REASMFAILS);
err:
@ -254,7 +255,8 @@ err:
* the last and the first frames arrived and all the bits are here.
*/
static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev)
struct sk_buff *prev_tail, struct net_device *dev,
int *refs)
{
struct net *net = fq->q.fqdir->net;
unsigned int nhoff;
@ -262,7 +264,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
int payload_len;
u8 ecn;
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
ecn = ip_frag_ecn_table[fq->ecn];
if (unlikely(ecn == 0xff))
@ -320,7 +322,7 @@ out_fail:
rcu_read_lock();
__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
rcu_read_unlock();
inet_frag_kill(&fq->q);
inet_frag_kill(&fq->q, refs);
return -1;
}
@ -386,7 +388,7 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
fq->iif = iif;
ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff,
&prob_offset);
&prob_offset, &refs);
spin_unlock(&fq->q.lock);
inet_frag_putn(&fq->q, refs);