From: Eric Dumazet <eduma...@google.com>
[ 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 fa76ce7328b2 ("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: fa76ce7328b2 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: Yuchung Cheng <ych...@google.com>
---
include/net/inet_connection_sock.h | 20 ---------------
include/net/request_sock.h | 18 --------------
net/dccp/ipv4.c | 3 +-
net/dccp/ipv6.c | 3 +-
net/dccp/minisocks.c | 3 --
net/ipv4/inet_connection_sock.c | 34 +++++++++++++++++++++++++++
net/ipv4/tcp_ipv4.c | 3 +-
net/ipv4/tcp_minisocks.c | 7 +++--
net/ipv6/tcp_ipv6.c | 3 +-
9 files changed, 48 insertions(+), 46 deletions(-)
diff --git a/include/net/inet_connection_sock.h
b/include/net/inet_connection_sock.h
index 7b5887cd1172..48a815823587 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -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);
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index fe41f3ceb008..9f4265ce8892 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -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,
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 2b4f21d34df6..ccf4c5629b3c 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -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,
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 9d0551092c6c..5165571f397a 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -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,
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 5f566663e47f..30addee2dd03 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -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;
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 5c3dd6267ed3..8976ca423a07 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -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;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3571f2be4470..fc1c658ec6c1 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -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;
}
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 63d6311b5365..2c6abb40cf5f 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -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:
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ad51df85aa00..b6575d665568 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -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,
--
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