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authorZach Brown <zach.brown@oracle.com>2006-04-10 16:05:34 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2006-04-11 17:21:05 -0700
commitf6596f9d2b4f0255f6cd68c76b85fe4cec6352af (patch)
tree6e95cca360198b2e546904d17760ba71d1dc5ee8 /net/ipv6/reassembly.c
parenta145410dccdb44f81d3b56763ef9b6f721f4e47c (diff)
downloadlwn-f6596f9d2b4f0255f6cd68c76b85fe4cec6352af.tar.gz
lwn-f6596f9d2b4f0255f6cd68c76b85fe4cec6352af.zip
[IPv6] reassembly: Always compute hash under the fragment lock.
This closes a race where an ipq6hashfn() caller could get a hash value and race with the cycling of the random seed. By the time they got to the read_lock they'd have a stale hash value and might not find previous fragments of their datagram. This matches the previous patch to IPv4. Signed-off-by: Zach Brown <zach.brown@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/reassembly.c')
-rw-r--r--net/ipv6/reassembly.c18
1 files changed, 12 insertions, 6 deletions
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index b67a45fb93e9..eef985e010ea 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -121,6 +121,10 @@ static __inline__ void fq_unlink(struct frag_queue *fq)
write_unlock(&ip6_frag_lock);
}
+/*
+ * callers should be careful not to use the hash value outside the ipfrag_lock
+ * as doing so could race with ipfrag_hash_rnd being recalculated.
+ */
static unsigned int ip6qhashfn(u32 id, struct in6_addr *saddr,
struct in6_addr *daddr)
{
@@ -324,15 +328,16 @@ out:
/* Creation primitives. */
-static struct frag_queue *ip6_frag_intern(unsigned int hash,
- struct frag_queue *fq_in)
+static struct frag_queue *ip6_frag_intern(struct frag_queue *fq_in)
{
struct frag_queue *fq;
+ unsigned int hash;
#ifdef CONFIG_SMP
struct hlist_node *n;
#endif
write_lock(&ip6_frag_lock);
+ hash = ip6qhashfn(fq_in->id, &fq_in->saddr, &fq_in->daddr);
#ifdef CONFIG_SMP
hlist_for_each_entry(fq, n, &ip6_frag_hash[hash], list) {
if (fq->id == fq_in->id &&
@@ -362,7 +367,7 @@ static struct frag_queue *ip6_frag_intern(unsigned int hash,
static struct frag_queue *
-ip6_frag_create(unsigned int hash, u32 id, struct in6_addr *src, struct in6_addr *dst)
+ip6_frag_create(u32 id, struct in6_addr *src, struct in6_addr *dst)
{
struct frag_queue *fq;
@@ -379,7 +384,7 @@ ip6_frag_create(unsigned int hash, u32 id, struct in6_addr *src, struct in6_addr
spin_lock_init(&fq->lock);
atomic_set(&fq->refcnt, 1);
- return ip6_frag_intern(hash, fq);
+ return ip6_frag_intern(fq);
oom:
IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
@@ -391,9 +396,10 @@ fq_find(u32 id, struct in6_addr *src, struct in6_addr *dst)
{
struct frag_queue *fq;
struct hlist_node *n;
- unsigned int hash = ip6qhashfn(id, src, dst);
+ unsigned int hash;
read_lock(&ip6_frag_lock);
+ hash = ip6qhashfn(id, src, dst);
hlist_for_each_entry(fq, n, &ip6_frag_hash[hash], list) {
if (fq->id == id &&
ipv6_addr_equal(src, &fq->saddr) &&
@@ -405,7 +411,7 @@ fq_find(u32 id, struct in6_addr *src, struct in6_addr *dst)
}
read_unlock(&ip6_frag_lock);
- return ip6_frag_create(hash, id, src, dst);
+ return ip6_frag_create(id, src, dst);
}