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Date: Sat, 15 Oct 2011 00:45:04 -0400
From: Matthew Daley <mattjd@...il.com>
To: netdev@...r.kernel.org
Cc: Eric Dumazet <eric.dumazet@...il.com>,
Andrew Hendry <andrew.hendry@...il.com>,
Matthew Daley <mattjd@...il.com>, stable <stable@...nel.org>
Subject: [PATCH 2/3] x25: Handle undersized/fragmented skbs
There are multiple locations in the X.25 packet layer where a skb is
assumed to be of at least a certain size and that all its data is
currently available at skb->data. These assumptions are not checked,
hence buffer overreads may occur. Use pskb_may_pull to check these
minimal size assumptions and ensure that data is available at skb->data
when necessary, as well as use skb_copy_bits where needed.
Signed-off-by: Matthew Daley <mattjd@...il.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Andrew Hendry <andrew.hendry@...il.com>
Cc: stable <stable@...nel.org>
---
net/x25/af_x25.c | 31 ++++++++++++++++++++++++-------
net/x25/x25_dev.c | 6 ++++++
net/x25/x25_facilities.c | 10 ++++++----
net/x25/x25_in.c | 40 +++++++++++++++++++++++++++++++++++-----
net/x25/x25_link.c | 3 +++
net/x25/x25_subr.c | 14 +++++++++++++-
6 files changed, 87 insertions(+), 17 deletions(-)
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index a4bd172..aa567b0 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -91,7 +91,7 @@ int x25_parse_address_block(struct sk_buff *skb,
int needed;
int rc;
- if (skb->len < 1) {
+ if (!pskb_may_pull(skb, 1)) {
/* packet has no address block */
rc = 0;
goto empty;
@@ -100,7 +100,7 @@ int x25_parse_address_block(struct sk_buff *skb,
len = *skb->data;
needed = 1 + (len >> 4) + (len & 0x0f);
- if (skb->len < needed) {
+ if (!pskb_may_pull(skb, needed)) {
/* packet is too short to hold the addresses it claims
to hold */
rc = -1;
@@ -951,10 +951,10 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
*
* Facilities length is mandatory in call request packets
*/
- if (skb->len < 1)
+ if (!pskb_may_pull(skb, 1))
goto out_clear_request;
len = skb->data[0] + 1;
- if (skb->len < len)
+ if (!pskb_may_pull(skb, len))
goto out_clear_request;
skb_pull(skb,len);
@@ -965,6 +965,13 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
goto out_clear_request;
/*
+ * Get all the call user data so it can be used in
+ * x25_find_listener and skb_copy_from_linear_data up ahead.
+ */
+ if (!pskb_may_pull(skb, skb->len))
+ goto out_clear_request;
+
+ /*
* Find a listener for the particular address/cud pair.
*/
sk = x25_find_listener(&source_addr,skb);
@@ -1172,6 +1179,9 @@ static int x25_sendmsg(struct kiocb *iocb, struct socket *sock,
* byte of the user data is the logical value of the Q Bit.
*/
if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
+ if (!pskb_may_pull(skb, 1))
+ goto out_kfree_skb;
+
qbit = skb->data[0];
skb_pull(skb, 1);
}
@@ -1250,7 +1260,9 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
struct x25_sock *x25 = x25_sk(sk);
struct sockaddr_x25 *sx25 = (struct sockaddr_x25 *)msg->msg_name;
size_t copied;
- int qbit;
+ int qbit, header_len = x25->neighbour->extended ?
+ X25_EXT_MIN_LEN : X25_STD_MIN_LEN;
+
struct sk_buff *skb;
unsigned char *asmptr;
int rc = -ENOTCONN;
@@ -1271,6 +1283,9 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
skb = skb_dequeue(&x25->interrupt_in_queue);
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ goto out_free_dgram;
+
skb_pull(skb, X25_STD_MIN_LEN);
/*
@@ -1291,10 +1306,12 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
if (!skb)
goto out;
+ if (!pskb_may_pull(skb, header_len))
+ goto out_free_dgram;
+
qbit = (skb->data[0] & X25_Q_BIT) == X25_Q_BIT;
- skb_pull(skb, x25->neighbour->extended ?
- X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
+ skb_pull(skb, header_len);
if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
asmptr = skb_push(skb, 1);
diff --git a/net/x25/x25_dev.c b/net/x25/x25_dev.c
index e547ca1..fa2b418 100644
--- a/net/x25/x25_dev.c
+++ b/net/x25/x25_dev.c
@@ -32,6 +32,9 @@ static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
unsigned short frametype;
unsigned int lci;
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ return 0;
+
frametype = skb->data[2];
lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
@@ -115,6 +118,9 @@ int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
goto drop;
}
+ if (!pskb_may_pull(skb, 1))
+ return 0;
+
switch (skb->data[0]) {
case X25_IFACE_DATA:
diff --git a/net/x25/x25_facilities.c b/net/x25/x25_facilities.c
index f77e4e7..36384a1 100644
--- a/net/x25/x25_facilities.c
+++ b/net/x25/x25_facilities.c
@@ -44,7 +44,7 @@
int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
{
- unsigned char *p = skb->data;
+ unsigned char *p;
unsigned int len;
*vc_fac_mask = 0;
@@ -60,14 +60,16 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
- if (skb->len < 1)
+ if (!pskb_may_pull(skb, 1))
return 0;
- len = *p++;
+ len = skb->data[0];
- if (len >= skb->len)
+ if (!pskb_may_pull(skb, 1 + len))
return -1;
+ p = skb->data + 1;
+
while (len > 0) {
switch (*p & X25_FAC_CLASS_MASK) {
case X25_FAC_CLASS_A:
diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
index 63488fd..a49cd4e 100644
--- a/net/x25/x25_in.c
+++ b/net/x25/x25_in.c
@@ -107,6 +107,8 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
/*
* Parse the data in the frame.
*/
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ goto out_clear;
skb_pull(skb, X25_STD_MIN_LEN);
len = x25_parse_address_block(skb, &source_addr,
@@ -130,9 +132,8 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
if (skb->len > X25_MAX_CUD_LEN)
goto out_clear;
- skb_copy_from_linear_data(skb,
- x25->calluserdata.cuddata,
- skb->len);
+ skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
+ skb->len);
x25->calluserdata.cudlength = skb->len;
}
if (!sock_flag(sk, SOCK_DEAD))
@@ -140,6 +141,9 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
break;
}
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
break;
@@ -167,6 +171,9 @@ static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametyp
switch (frametype) {
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
@@ -180,6 +187,11 @@ static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametyp
}
return 0;
+
+out_clear:
+ x25_write_internal(sk, X25_CLEAR_REQUEST);
+ x25_start_t23timer(sk);
+ return 0;
}
/*
@@ -209,6 +221,9 @@ static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametyp
break;
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
@@ -307,6 +322,12 @@ static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametyp
}
return queued;
+
+out_clear:
+ x25_write_internal(sk, X25_CLEAR_REQUEST);
+ x25->state = X25_STATE_2;
+ x25_start_t23timer(sk);
+ return 0;
}
/*
@@ -316,13 +337,13 @@ static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametyp
*/
static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
{
+ struct x25_sock *x25 = x25_sk(sk);
+
switch (frametype) {
case X25_RESET_REQUEST:
x25_write_internal(sk, X25_RESET_CONFIRMATION);
case X25_RESET_CONFIRMATION: {
- struct x25_sock *x25 = x25_sk(sk);
-
x25_stop_timer(sk);
x25->condition = 0x00;
x25->va = 0;
@@ -334,6 +355,9 @@ static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametyp
break;
}
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
@@ -343,6 +367,12 @@ static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametyp
}
return 0;
+
+out_clear:
+ x25_write_internal(sk, X25_CLEAR_REQUEST);
+ x25->state = X25_STATE_2;
+ x25_start_t23timer(sk);
+ return 0;
}
/* Higher level upcall for a LAPB frame */
diff --git a/net/x25/x25_link.c b/net/x25/x25_link.c
index 037958f..4acacf3 100644
--- a/net/x25/x25_link.c
+++ b/net/x25/x25_link.c
@@ -90,6 +90,9 @@ void x25_link_control(struct sk_buff *skb, struct x25_neigh *nb,
break;
case X25_DIAGNOSTIC:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 4))
+ break;
+
printk(KERN_WARNING "x25: diagnostic #%d - %02X %02X %02X\n",
skb->data[3], skb->data[4],
skb->data[5], skb->data[6]);
diff --git a/net/x25/x25_subr.c b/net/x25/x25_subr.c
index 24a342e..5170d52 100644
--- a/net/x25/x25_subr.c
+++ b/net/x25/x25_subr.c
@@ -269,7 +269,11 @@ int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
int *d, int *m)
{
struct x25_sock *x25 = x25_sk(sk);
- unsigned char *frame = skb->data;
+ unsigned char *frame;
+
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ return X25_ILLEGAL;
+ frame = skb->data;
*ns = *nr = *q = *d = *m = 0;
@@ -294,6 +298,10 @@ int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
if (frame[2] == X25_RR ||
frame[2] == X25_RNR ||
frame[2] == X25_REJ) {
+ if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
+ return X25_ILLEGAL;
+ frame = skb->data;
+
*nr = (frame[3] >> 1) & 0x7F;
return frame[2];
}
@@ -308,6 +316,10 @@ int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
if (x25->neighbour->extended) {
if ((frame[2] & 0x01) == X25_DATA) {
+ if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
+ return X25_ILLEGAL;
+ frame = skb->data;
+
*q = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
*d = (frame[0] & X25_D_BIT) == X25_D_BIT;
*m = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
--
1.7.2.5
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