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authorEric Dumazet <eric.dumazet@gmail.com>2010-11-25 04:11:39 +0000
committerDavid S. Miller <davem@davemloft.net>2010-11-29 09:45:15 -0800
commit25888e30319f8896fc656fc68643e6a078263060 (patch)
treeae484d38b1250da885d3939dd9a97e667fbc871d
parent50a4205333c5e545551f1f82b3004ca635407c5c (diff)
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af_unix: limit recursion level
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>
-rw-r--r--include/net/af_unix.h2
-rw-r--r--net/unix/af_unix.c37
-rw-r--r--net/unix/garbage.c2
3 files changed, 35 insertions, 6 deletions
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;