From 9915672d41273f5b77f1b3c29b391ffb7732b84b Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 24 Nov 2010 09:15:27 -0800
Subject: af_unix: limit unix_tot_inflight
Vegard Nossum found a unix socket OOM was possible, posting an exploit
program.
My analysis is we can eat all LOWMEM memory before unix_gc() being
called from unix_release_sock(). Moreover, the thread blocked in
unix_gc() can consume huge amount of time to perform cleanup because of
huge working set.
One way to handle this is to have a sensible limit on unix_tot_inflight,
tested from wait_for_unix_gc() and to force a call to unix_gc() if this
limit is hit.
This solves the OOM and also reduce overall latencies, and should not
slowdown normal workloads.
Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/unix/garbage.c | 7 +++++++
1 file changed, 7 insertions(+)
(limited to 'net/unix/garbage.c')
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index c8df6fda0b1..40df93d1cf3 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -259,9 +259,16 @@ static void inc_inflight_move_tail(struct unix_sock *u)
}
static bool gc_in_progress = false;
+#define UNIX_INFLIGHT_TRIGGER_GC 16000
void wait_for_unix_gc(void)
{
+ /*
+ * If number of inflight sockets is insane,
+ * force a garbage collect right now.
+ */
+ if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
+ unix_gc();
wait_event(unix_gc_wait, gc_in_progress == false);
}
--
cgit v1.2.3-70-g09d2
From 25888e30319f8896fc656fc68643e6a078263060 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 25 Nov 2010 04:11:39 +0000
Subject: af_unix: limit recursion level
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Its easy to eat all kernel memory and trigger NMI watchdog, using an
exploit program that queues unix sockets on top of others.
lkml ref : http://lkml.org/lkml/2010/11/25/8
This mechanism is used in applications, one choice we have is to have a
recursion limit.
Other limits might be needed as well (if we queue other types of files),
since the passfd mechanism is currently limited by socket receive queue
sizes only.
Add a recursion_level to unix socket, allowing up to 4 levels.
Each time we send an unix socket through sendfd mechanism, we copy its
recursion level (plus one) to receiver. This recursion level is cleared
when socket receive queue is emptied.
Reported-by: Марк Коренберг <socketpair@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/net/af_unix.h | 2 ++
net/unix/af_unix.c | 37 ++++++++++++++++++++++++++++++++-----
net/unix/garbage.c | 2 +-
3 files changed, 35 insertions(+), 6 deletions(-)
(limited to 'net/unix/garbage.c')
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 90c9e2872f2..18e5c3f6758 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -10,6 +10,7 @@ extern void unix_inflight(struct file *fp);
extern void unix_notinflight(struct file *fp);
extern void unix_gc(void);
extern void wait_for_unix_gc(void);
+extern struct sock *unix_get_socket(struct file *filp);
#define UNIX_HASH_SIZE 256
@@ -56,6 +57,7 @@ struct unix_sock {
spinlock_t lock;
unsigned int gc_candidate : 1;
unsigned int gc_maybe_cycle : 1;
+ unsigned char recursion_level;
struct socket_wq peer_wq;
};
#define unix_sk(__sk) ((struct unix_sock *)__sk)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 3c95304a081..2268e679812 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1343,9 +1343,25 @@ static void unix_destruct_scm(struct sk_buff *skb)
sock_wfree(skb);
}
+#define MAX_RECURSION_LEVEL 4
+
static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
{
int i;
+ unsigned char max_level = 0;
+ int unix_sock_count = 0;
+
+ for (i = scm->fp->count - 1; i >= 0; i--) {
+ struct sock *sk = unix_get_socket(scm->fp->fp[i]);
+
+ if (sk) {
+ unix_sock_count++;
+ max_level = max(max_level,
+ unix_sk(sk)->recursion_level);
+ }
+ }
+ if (unlikely(max_level > MAX_RECURSION_LEVEL))
+ return -ETOOMANYREFS;
/*
* Need to duplicate file references for the sake of garbage
@@ -1356,9 +1372,11 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
if (!UNIXCB(skb).fp)
return -ENOMEM;
- for (i = scm->fp->count-1; i >= 0; i--)
- unix_inflight(scm->fp->fp[i]);
- return 0;
+ if (unix_sock_count) {
+ for (i = scm->fp->count - 1; i >= 0; i--)
+ unix_inflight(scm->fp->fp[i]);
+ }
+ return max_level;
}
static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool send_fds)
@@ -1393,6 +1411,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
struct sk_buff *skb;
long timeo;
struct scm_cookie tmp_scm;
+ int max_level;
if (NULL == siocb->scm)
siocb->scm = &tmp_scm;
@@ -1431,8 +1450,9 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
goto out;
err = unix_scm_to_skb(siocb->scm, skb, true);
- if (err)
+ if (err < 0)
goto out_free;
+ max_level = err + 1;
unix_get_secdata(siocb->scm, skb);
skb_reset_transport_header(skb);
@@ -1514,6 +1534,8 @@ restart:
if (sock_flag(other, SOCK_RCVTSTAMP))
__net_timestamp(skb);
skb_queue_tail(&other->sk_receive_queue, skb);
+ if (max_level > unix_sk(other)->recursion_level)
+ unix_sk(other)->recursion_level = max_level;
unix_state_unlock(other);
other->sk_data_ready(other, len);
sock_put(other);
@@ -1544,6 +1566,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
int sent = 0;
struct scm_cookie tmp_scm;
bool fds_sent = false;
+ int max_level;
if (NULL == siocb->scm)
siocb->scm = &tmp_scm;
@@ -1607,10 +1630,11 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
/* Only send the fds in the first buffer */
err = unix_scm_to_skb(siocb->scm, skb, !fds_sent);
- if (err) {
+ if (err < 0) {
kfree_skb(skb);
goto out_err;
}
+ max_level = err + 1;
fds_sent = true;
err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);
@@ -1626,6 +1650,8 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
goto pipe_err_free;
skb_queue_tail(&other->sk_receive_queue, skb);
+ if (max_level > unix_sk(other)->recursion_level)
+ unix_sk(other)->recursion_level = max_level;
unix_state_unlock(other);
other->sk_data_ready(other, size);
sent += size;
@@ -1845,6 +1871,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
unix_state_lock(sk);
skb = skb_dequeue(&sk->sk_receive_queue);
if (skb == NULL) {
+ unix_sk(sk)->recursion_level = 0;
if (copied >= target)
goto unlock;
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 40df93d1cf3..f89f83bf828 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -96,7 +96,7 @@ static DECLARE_WAIT_QUEUE_HEAD(unix_gc_wait);
unsigned int unix_tot_inflight;
-static struct sock *unix_get_socket(struct file *filp)
+struct sock *unix_get_socket(struct file *filp)
{
struct sock *u_sock = NULL;
struct inode *inode = filp->f_path.dentry->d_inode;
--
cgit v1.2.3-70-g09d2