Skip to contentSkip to conversation

sunrpc: safely reallow resvport min/max inversion

PATCH New J. Bruce Fields 1 participant 3 messages Sep 17, 2018 – Oct 19, 2018 2 messages not in the archive

Subsystems (3)
Networking NFS client NFS server
lore
Share & tools
lore

A message that is not in the archive (sent off-list or not yet received): [email protected]

A message that is not in the archive (sent off-list or not yet received): [email protected]

J. Bruce Fields

author
#2 lore raw

From: "J. Bruce Fields" <[email protected]>

Commits ffb6ca33b04b and e08ea3a96fc7 prevent setting xprt_min_resvport greater than xprt_max_resvport, but may also break simple code that sets one parameter then the other, if the new range does not overlap the old.

Also it looks racy to me, unless there's some serialization I'm not seeing. Granted it would probably require malicious privileged processes (unless there's a chance these might eventually be settable in unprivileged containers), but still it seems better not to let userspace panic the kernel.

Simpler seems to be to allow setting the parameters to whatever you want but interpret xprt_min_resvport > xprt_max_resvport as the empty range.

Untested.

Fixes ffb6ca33b04b "sunrpc: Prevent resvport min/max inversion..."
Fixes e08ea3a96fc7 "sunrpc: Prevent rexvport min/max inversion..."
Signed-off-by J. Bruce Fields <[email protected]>
---
 net/sunrpc/xprtsock.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

Whoops, I sent this before but just noticed that I failed to cc the list, then that I mispelled the address. Argh.

net/sunrpc/xprtsock.c +18 -16
index 9e1c5024aba9..5d59de92b5a1 100644
@@ -129,7 +129,7 @@ static struct ctl_table xs_tunables_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &xprt_min_resvport_limit,
-		.extra2		= &xprt_max_resvport
+		.extra2		= &xprt_max_resvport_limit
 	},
 	{
 		.procname	= "max_resvport",

@@ -137,7 +137,7 @@ static struct ctl_table xs_tunables_table[] = {
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &xprt_min_resvport,
+		.extra1		= &xprt_min_resvport_limit,
 		.extra2		= &xprt_max_resvport_limit
 	},
 	{

@@ -1773,11 +1773,17 @@ static void xs_udp_timer(struct rpc_xprt *xprt, struct rpc_task *task)
 	spin_unlock_bh(&xprt->transport_lock);
 }
 
-static unsigned short xs_get_random_port(void)
+static int xs_get_random_port(void)
 {
-	unsigned short range = xprt_max_resvport - xprt_min_resvport + 1;
-	unsigned short rand = (unsigned short) prandom_u32() % range;
-	return rand + xprt_min_resvport;
+	unsigned short min = xprt_min_resvport, max = xprt_max_resvport;
+	unsigned short range;
+	unsigned short rand;
+
+	if (max < min)
+		return -EADDRINUSE;
+	range = max - min + 1;
+	rand = (unsigned short) prandom_u32() % range;
+	return rand + min;
 }
 
 /**

@@ -1833,9 +1839,9 @@ static void xs_set_srcport(struct sock_xprt *transport, struct socket *sock)
 		transport->srcport = xs_sock_getport(sock);
 }
 
-static unsigned short xs_get_srcport(struct sock_xprt *transport)
+static int xs_get_srcport(struct sock_xprt *transport)
 {
-	unsigned short port = transport->srcport;
+	int port = transport->srcport;
 
 	if (port == 0 && transport->xprt.resvport)
 		port = xs_get_random_port();

@@ -1856,7 +1862,7 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 {
 	struct sockaddr_storage myaddr;
 	int err, nloop = 0;
-	unsigned short port = xs_get_srcport(transport);
+	int port = xs_get_srcport(transport);
 	unsigned short last;
 
 	/*

@@ -1874,8 +1880,8 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 	 * transport->xprt.resvport == 1) xs_get_srcport above will
 	 * ensure that port is non-zero and we will bind as needed.
 	 */
-	if (port == 0)
-		return 0;
+	if (port <= 0)
+		return port;
 
 	memcpy(&myaddr, &transport->srcaddr, transport->xprt.addrlen);
 	do {

@@ -3317,12 +3323,8 @@ static int param_set_uint_minmax(const char *val,
 
 static int param_set_portnr(const char *val, const struct kernel_param *kp)
 {
-	if (kp->arg == &xprt_min_resvport)
-		return param_set_uint_minmax(val, kp,
-			RPC_MIN_RESVPORT,
-			xprt_max_resvport);
 	return param_set_uint_minmax(val, kp,
-			xprt_min_resvport,
+			RPC_MIN_RESVPORT,
 			RPC_MAX_RESVPORT);
 }
Signature · 1 line
2.17.1
author
#3 lore raw

I didn't get any feedback on this patch. Maybe the problem was this:

Quoted 12 lines · J. Bruce Fields

From: "J. Bruce Fields" <[email protected]>

Commits ffb6ca33b04b and e08ea3a96fc7 prevent setting xprt_min_resvport greater than xprt_max_resvport, but may also break simple code that sets one parameter then the other, if the new range does not overlap the old.

Also it looks racy to me, unless there's some serialization I'm not seeing. Granted it would probably require malicious privileged processes (unless there's a chance these might eventually be settable in unprivileged containers), but still it seems better not to let userspace panic the kernel.

Quoted 4 lines

Simpler seems to be to allow setting the parameters to whatever you want but interpret xprt_min_resvport > xprt_max_resvport as the empty range.

Untested.

So, I've booted to it and verified that I can set min_resvport and max_resvport, and that mount fails when min_resvport > max_resvport.

I'll resend.

--b.

Quoted 104 lines
Fixes ffb6ca33b04b "sunrpc: Prevent resvport min/max inversion..."
Fixes e08ea3a96fc7 "sunrpc: Prevent rexvport min/max inversion..."
Signed-off-by J. Bruce Fields <[email protected]>
---
 net/sunrpc/xprtsock.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

Whoops, I sent this before but just noticed that I failed to cc the list, then that I mispelled the address. Argh.

net/sunrpc/xprtsock.c +18 -16
index 9e1c5024aba9..5d59de92b5a1 100644
@@ -129,7 +129,7 @@ static struct ctl_table xs_tunables_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &xprt_min_resvport_limit,
-		.extra2		= &xprt_max_resvport
+		.extra2		= &xprt_max_resvport_limit
 	},
 	{
 		.procname	= "max_resvport",

@@ -137,7 +137,7 @@ static struct ctl_table xs_tunables_table[] = {
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &xprt_min_resvport,
+		.extra1		= &xprt_min_resvport_limit,
 		.extra2		= &xprt_max_resvport_limit
 	},
 	{

@@ -1773,11 +1773,17 @@ static void xs_udp_timer(struct rpc_xprt *xprt, struct rpc_task *task)
 	spin_unlock_bh(&xprt->transport_lock);
 }
 
-static unsigned short xs_get_random_port(void)
+static int xs_get_random_port(void)
 {
-	unsigned short range = xprt_max_resvport - xprt_min_resvport + 1;
-	unsigned short rand = (unsigned short) prandom_u32() % range;
-	return rand + xprt_min_resvport;
+	unsigned short min = xprt_min_resvport, max = xprt_max_resvport;
+	unsigned short range;
+	unsigned short rand;
+
+	if (max < min)
+		return -EADDRINUSE;
+	range = max - min + 1;
+	rand = (unsigned short) prandom_u32() % range;
+	return rand + min;
 }
 
 /**

@@ -1833,9 +1839,9 @@ static void xs_set_srcport(struct sock_xprt *transport, struct socket *sock)
 		transport->srcport = xs_sock_getport(sock);
 }
 
-static unsigned short xs_get_srcport(struct sock_xprt *transport)
+static int xs_get_srcport(struct sock_xprt *transport)
 {
-	unsigned short port = transport->srcport;
+	int port = transport->srcport;
 
 	if (port == 0 && transport->xprt.resvport)
 		port = xs_get_random_port();

@@ -1856,7 +1862,7 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 {
 	struct sockaddr_storage myaddr;
 	int err, nloop = 0;
-	unsigned short port = xs_get_srcport(transport);
+	int port = xs_get_srcport(transport);
 	unsigned short last;
 
 	/*

@@ -1874,8 +1880,8 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 	 * transport->xprt.resvport == 1) xs_get_srcport above will
 	 * ensure that port is non-zero and we will bind as needed.
 	 */
-	if (port == 0)
-		return 0;
+	if (port <= 0)
+		return port;
 
 	memcpy(&myaddr, &transport->srcaddr, transport->xprt.addrlen);
 	do {

@@ -3317,12 +3323,8 @@ static int param_set_uint_minmax(const char *val,
 
 static int param_set_portnr(const char *val, const struct kernel_param *kp)
 {
-	if (kp->arg == &xprt_min_resvport)
-		return param_set_uint_minmax(val, kp,
-			RPC_MIN_RESVPORT,
-			xprt_max_resvport);
 	return param_set_uint_minmax(val, kp,
-			xprt_min_resvport,
+			RPC_MIN_RESVPORT,
 			RPC_MAX_RESVPORT);
 }
Signature · 1 line
2.17.1
author
#4 lore raw

PATCH 1/1 sunrpc: safely reallow resvport min/max inversion

From: "J. Bruce Fields" <[email protected]>

Commits ffb6ca33b04b and e08ea3a96fc7 prevent setting xprt_min_resvport greater than xprt_max_resvport, but may also break simple code that sets one parameter then the other, if the new range does not overlap the old.

Also it looks racy to me, unless there's some serialization I'm not seeing. Granted it would probably require malicious privileged processes (unless there's a chance these might eventually be settable in unprivileged containers), but still it seems better not to let userspace panic the kernel.

Simpler seems to be to allow setting the parameters to whatever you want but interpret xprt_min_resvport > xprt_max_resvport as the empty range.

Fixes ffb6ca33b04b "sunrpc: Prevent resvport min/max inversion..."
Fixes e08ea3a96fc7 "sunrpc: Prevent rexvport min/max inversion..."
Signed-off-by J. Bruce Fields <[email protected]>
---
 net/sunrpc/xprtsock.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)
net/sunrpc/xprtsock.c +18 -16
index 6b7539c0466e..58219d7de91f 100644
@@ -129,7 +129,7 @@ static struct ctl_table xs_tunables_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &xprt_min_resvport_limit,
-		.extra2		= &xprt_max_resvport
+		.extra2		= &xprt_max_resvport_limit
 	},
 	{
 		.procname	= "max_resvport",

@@ -137,7 +137,7 @@ static struct ctl_table xs_tunables_table[] = {
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &xprt_min_resvport,
+		.extra1		= &xprt_min_resvport_limit,
 		.extra2		= &xprt_max_resvport_limit
 	},
 	{

@@ -1773,11 +1773,17 @@ static void xs_udp_timer(struct rpc_xprt *xprt, struct rpc_task *task)
 	spin_unlock_bh(&xprt->transport_lock);
 }
 
-static unsigned short xs_get_random_port(void)
+static int xs_get_random_port(void)
 {
-	unsigned short range = xprt_max_resvport - xprt_min_resvport + 1;
-	unsigned short rand = (unsigned short) prandom_u32() % range;
-	return rand + xprt_min_resvport;
+	unsigned short min = xprt_min_resvport, max = xprt_max_resvport;
+	unsigned short range;
+	unsigned short rand;
+
+	if (max < min)
+		return -EADDRINUSE;
+	range = max - min + 1;
+	rand = (unsigned short) prandom_u32() % range;
+	return rand + min;
 }
 
 /**

@@ -1833,9 +1839,9 @@ static void xs_set_srcport(struct sock_xprt *transport, struct socket *sock)
 		transport->srcport = xs_sock_getport(sock);
 }
 
-static unsigned short xs_get_srcport(struct sock_xprt *transport)
+static int xs_get_srcport(struct sock_xprt *transport)
 {
-	unsigned short port = transport->srcport;
+	int port = transport->srcport;
 
 	if (port == 0 && transport->xprt.resvport)
 		port = xs_get_random_port();

@@ -1856,7 +1862,7 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 {
 	struct sockaddr_storage myaddr;
 	int err, nloop = 0;
-	unsigned short port = xs_get_srcport(transport);
+	int port = xs_get_srcport(transport);
 	unsigned short last;
 
 	/*

@@ -1874,8 +1880,8 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 	 * transport->xprt.resvport == 1) xs_get_srcport above will
 	 * ensure that port is non-zero and we will bind as needed.
 	 */
-	if (port == 0)
-		return 0;
+	if (port <= 0)
+		return port;
 
 	memcpy(&myaddr, &transport->srcaddr, transport->xprt.addrlen);
 	do {

@@ -3317,12 +3323,8 @@ static int param_set_uint_minmax(const char *val,
 
 static int param_set_portnr(const char *val, const struct kernel_param *kp)
 {
-	if (kp->arg == &xprt_min_resvport)
-		return param_set_uint_minmax(val, kp,
-			RPC_MIN_RESVPORT,
-			xprt_max_resvport);
 	return param_set_uint_minmax(val, kp,
-			xprt_min_resvport,
+			RPC_MIN_RESVPORT,
 			RPC_MAX_RESVPORT);
 }
Signature · 1 line
2.17.2