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inet: fix possible panic in reqsk_queue_unlink()

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[ 3897.923145] BUG: unable to handle kernel NULL pointer dereference at
 0000000000000080
[ 3897.931025] IP: [<ffffffffa9f27686>] reqsk_timer_handler+0x1a6/0x243

There is a race when reqsk_timer_handler() and tcp_check_req() call
inet_csk_reqsk_queue_unlink() on the same req at the same time.

Before commit fa76ce7328 ("inet: get rid of central tcp/dccp listener
timer"), listener spinlock was held and race could not happen.

To solve this bug, we change reqsk_queue_unlink() to not assume req
must be found, and we return a status, to conditionally release a
refcount on the request sock.

This also means tcp_check_req() in non fastopen case might or not
consume req refcount, so tcp_v6_hnd_req() & tcp_v4_hnd_req() have
to properly handle this.

(Same remark for dccp_check_req() and its callers)

inet_csk_reqsk_queue_drop() is now too big to be inlined, as it is
called 4 times in tcp and 3 times in dccp.

Fixes: fa76ce7328 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-04-23 18:03:44 -07:00 committed by David S. Miller
parent 1d8dc3d3c8
commit b357a364c5
9 changed files with 48 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
include/net/inet_connection_sock.h
View File

@ -279,12 +279,6 @@ static inline void inet_csk_reqsk_queue_add(struct sock *sk,
void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
unsigned long timeout);
static inline void inet_csk_reqsk_queue_removed(struct sock *sk,
struct request_sock *req)
{
reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
}
static inline void inet_csk_reqsk_queue_added(struct sock *sk,
const unsigned long timeout)
{
@ -306,19 +300,7 @@ static inline int inet_csk_reqsk_queue_is_full(const struct sock *sk)
return reqsk_queue_is_full(&inet_csk(sk)->icsk_accept_queue);
}
static inline void inet_csk_reqsk_queue_unlink(struct sock *sk,
struct request_sock *req)
{
reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req);
}
static inline void inet_csk_reqsk_queue_drop(struct sock *sk,
struct request_sock *req)
{
inet_csk_reqsk_queue_unlink(sk, req);
inet_csk_reqsk_queue_removed(sk, req);
reqsk_put(req);
}
void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req);
void inet_csk_destroy_sock(struct sock *sk);
void inet_csk_prepare_forced_close(struct sock *sk);

18
include/net/request_sock.h
View File

@ -212,24 +212,6 @@ static inline int reqsk_queue_empty(struct request_sock_queue *queue)
return queue->rskq_accept_head == NULL;
}
static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
struct request_sock *req)
{
struct listen_sock *lopt = queue->listen_opt;
struct request_sock **prev;
spin_lock(&queue->syn_wait_lock);
prev = &lopt->syn_table[req->rsk_hash];
while (*prev != req)
prev = &(*prev)->dl_next;
*prev = req->dl_next;
spin_unlock(&queue->syn_wait_lock);
if (del_timer(&req->rsk_timer))
reqsk_put(req);
}
static inline void reqsk_queue_add(struct request_sock_queue *queue,
struct request_sock *req,
struct sock *parent,

3
net/dccp/ipv4.c
View File

@ -453,7 +453,8 @@ static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
iph->saddr, iph->daddr);
if (req) {
nsk = dccp_check_req(sk, skb, req);
reqsk_put(req);
if (!nsk)
reqsk_put(req);
return nsk;
}
nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,

3
net/dccp/ipv6.c
View File

@ -301,7 +301,8 @@ static struct sock *dccp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
&iph->daddr, inet6_iif(skb));
if (req) {
nsk = dccp_check_req(sk, skb, req);
reqsk_put(req);
if (!nsk)
reqsk_put(req);
return nsk;
}
nsk = __inet6_lookup_established(sock_net(sk), &dccp_hashinfo,

3
net/dccp/minisocks.c
View File

@ -186,8 +186,7 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
if (child == NULL)
goto listen_overflow;
inet_csk_reqsk_queue_unlink(sk, req);
inet_csk_reqsk_queue_removed(sk, req);
inet_csk_reqsk_queue_drop(sk, req);
inet_csk_reqsk_queue_add(sk, req, child);
out:
return child;

34
net/ipv4/inet_connection_sock.c
View File

@ -564,6 +564,40 @@ int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req)
}
EXPORT_SYMBOL(inet_rtx_syn_ack);
/* return true if req was found in the syn_table[] */
static bool reqsk_queue_unlink(struct request_sock_queue *queue,
struct request_sock *req)
{
struct listen_sock *lopt = queue->listen_opt;
struct request_sock **prev;
bool found = false;
spin_lock(&queue->syn_wait_lock);
for (prev = &lopt->syn_table[req->rsk_hash]; *prev != NULL;
prev = &(*prev)->dl_next) {
if (*prev == req) {
*prev = req->dl_next;
found = true;
break;
}
}
spin_unlock(&queue->syn_wait_lock);
if (del_timer(&req->rsk_timer))
reqsk_put(req);
return found;
}
void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req)
{
if (reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req)) {
reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
reqsk_put(req);
}
}
EXPORT_SYMBOL(inet_csk_reqsk_queue_drop);
static void reqsk_timer_handler(unsigned long data)
{
struct request_sock *req = (struct request_sock *)data;

3
net/ipv4/tcp_ipv4.c
View File

@ -1348,7 +1348,8 @@ static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
req = inet_csk_search_req(sk, th->source, iph->saddr, iph->daddr);
if (req) {
nsk = tcp_check_req(sk, skb, req, false);
reqsk_put(req);
if (!nsk)
reqsk_put(req);
return nsk;
}

7
net/ipv4/tcp_minisocks.c
View File

@ -755,10 +755,11 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
if (!child)
goto listen_overflow;
inet_csk_reqsk_queue_unlink(sk, req);
inet_csk_reqsk_queue_removed(sk, req);
inet_csk_reqsk_queue_drop(sk, req);
inet_csk_reqsk_queue_add(sk, req, child);
/* Warning: caller must not call reqsk_put(req);
* child stole last reference on it.
*/
return child;
listen_overflow:

3
net/ipv6/tcp_ipv6.c
View File

@ -946,7 +946,8 @@ static struct sock *tcp_v6_hnd_req(struct sock *sk, struct sk_buff *skb)
&ipv6_hdr(skb)->daddr, tcp_v6_iif(skb));
if (req) {
nsk = tcp_check_req(sk, skb, req, false);
reqsk_put(req);
if (!nsk)
reqsk_put(req);
return nsk;
}
nsk = __inet6_lookup_established(sock_net(sk), &tcp_hashinfo,