net: dccp: initialize (addr,port) listening hashtable [Linux 5.0]

net: dccp: initialize (addr,port) listening hashtable [Linux 5.0]

This Linux kernel change "net: dccp: initialize (addr,port) listening hashtable" is included in the Linux 5.0 release. This change is authored by Peter Oskolkov <posk [at]> on Sun Dec 16 15:42:48 2018 -0800. The commit for this change in Linux stable tree is eedbbb0 (patch).

net: dccp: initialize (addr,port) listening hashtable

Commit d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
removes port-only listener lookups. This caused segfaults in DCCP
lookups because DCCP did not initialize the (addr,port) hashtable.

This patch adds said initialization.

The only non-trivial issue here is the size of the new hashtable.
It seemed reasonable to make it match the size of the port-only
hashtable (= INET_LHTABLE_SIZE) that was used previously. Other
parameters to inet_hashinfo2_init() match those used in TCP.

V2 changes: marked inet_hashinfo2_init as an exported symbol
so that DCCP compiles when configured as a module.

Tested: syzcaller issues fixed; the second patch in the patchset
        tests that DCCP lookups work correctly.

Fixes: d9fbc7f6431f "net: tcp: prefer listeners bound to an address"
Reported-by: syzcaller <>
Signed-off-by: Peter Oskolkov <>
Signed-off-by: David S. Miller <>

There are 4 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/dccp/proto.c           | 3 +++
 net/ipv4/inet_hashtables.c | 1 +
 2 files changed, 4 insertions(+)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 658cd32b..be0b223 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1141,6 +1141,9 @@ static int __init dccp_init(void)
        goto out_fail;
    rc = -ENOBUFS;
+   inet_hashinfo2_init(&dccp_hashinfo, "dccp_listen_portaddr_hash",
+               INET_LHTABLE_SIZE, 21,  /* one slot per 2 MB*/
+               0, 64 * 1024);
    dccp_hashinfo.bind_bucket_cachep =
                  sizeof(struct inet_bind_bucket), 0,
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index cd03ab4..2445614 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -785,6 +785,7 @@ void __init inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
        h->lhash2[i].count = 0;

 int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)

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