Partial MFC of r342125:

Fix bugs in plugable CC algorithm and siftr sysctls. Use the sysctl_handle_int() handler to write out the old value and read the new value into a temporary variable. Use the temporary variable for any checks of values rather than using the CAST_PTR_INT() macro on req->newptr. The prior usage read directly from userspace memory if the sysctl() was called correctly. This is unsafe and doesn't work at all on some architectures (at least i386.) In some cases, the code could also be tricked into reading from kernel memory and leaking limited information about the contents or crashing the system. This was true for CDG, newreno, and siftr on all platforms and true for i386 in all cases. The impact of this bug is largest in VIMAGE jails which have been configured to allow writing to these sysctls. Per discussion with the security officer, we will not be issuing an advisory for this issue as root access and a non-default config are required to be impacted. Changes to sys/netinet/cc/cc_newreno.c are not merged as the sysctl's had not previously been merged. Reviewed by: markj, bz Discussed with: gordon (security officer) Security: kernel information leak, local DoS (both require root) Differential Revision: https://reviews.freebsd.org/D18443
HardenedBSD · Dec 18, 2018 · f445d2a · f445d2a
1 parent db4e6f3
commit f445d2a
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Showing 6 changed files with 49 additions and 51 deletions.
diff --git a/sys/netinet/cc/cc_cdg.c b/sys/netinet/cc/cc_cdg.c
@@ -78,8 +78,6 @@ __FBSDID("$FreeBSD$");
 
 #define	CDG_VERSION "0.1"
 
-#define	CAST_PTR_INT(X) (*((int*)(X)))
-
 /* Private delay-gradient induced congestion control signal. */
 #define	CC_CDG_DELAY 0x01000000
 
@@ -356,22 +354,37 @@ cdg_cb_destroy(struct cc_var *ccv)
 static int
 cdg_beta_handler(SYSCTL_HANDLER_ARGS)
 {
+	int error;
+	uint32_t new;
+
+	new = *(uint32_t *)arg1;
+	error = sysctl_handle_int(oidp, &new, 0, req);
+	if (error == 0 && req->newptr != NULL) {
+		if (new == 0 || new > 100)
+			error = EINVAL;
+		else
+			*(uint32_t *)arg1 = new;
+	}
 
-	if (req->newptr != NULL &&
-	    (CAST_PTR_INT(req->newptr) == 0 || CAST_PTR_INT(req->newptr) > 100))
-		return (EINVAL);
-
-	return (sysctl_handle_int(oidp, arg1, arg2, req));
+	return (error);
 }
 
 static int
 cdg_exp_backoff_scale_handler(SYSCTL_HANDLER_ARGS)
 {
+	int error;
+	uint32_t new;
+
+	new = *(uint32_t *)arg1;
+	error = sysctl_handle_int(oidp, &new, 0, req);
+	if (error == 0 && req->newptr != NULL) {
+		if (new < 1)
+			error = EINVAL;
+		else
+			*(uint32_t *)arg1 = new;
+	}
 
-	if (req->newptr != NULL && CAST_PTR_INT(req->newptr) < 1)
-		return (EINVAL);
-
-	return (sysctl_handle_int(oidp, arg1, arg2, req));
+	return (error);
 }
 
 static inline unsigned long

diff --git a/sys/netinet/cc/cc_chd.c b/sys/netinet/cc/cc_chd.c
@@ -76,8 +76,6 @@ __FBSDID("$FreeBSD$");
 
 #include <netinet/khelp/h_ertt.h>
 
-#define	CAST_PTR_INT(X)	(*((int*)(X)))
-
 /*
  * Private signal type for rate based congestion signal.
  * See <netinet/cc.h> for appropriate bit-range to use for private signals.
@@ -420,7 +418,7 @@ chd_loss_fair_handler(SYSCTL_HANDLER_ARGS)
 	new = V_chd_loss_fair;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) > 1)
+		if (new > 1)
 			error = EINVAL;
 		else
 			V_chd_loss_fair = new;
@@ -438,8 +436,7 @@ chd_pmax_handler(SYSCTL_HANDLER_ARGS)
 	new = V_chd_pmax;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) == 0 ||
-		    CAST_PTR_INT(req->newptr) > 100)
+		if (new == 0 || new > 100)
 			error = EINVAL;
 		else
 			V_chd_pmax = new;
@@ -457,7 +454,7 @@ chd_qthresh_handler(SYSCTL_HANDLER_ARGS)
 	new = V_chd_qthresh;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) <= V_chd_qmin)
+		if (new <= V_chd_qmin)
 			error = EINVAL;
 		else
 			V_chd_qthresh = new;

diff --git a/sys/netinet/cc/cc_dctcp.c b/sys/netinet/cc/cc_dctcp.c
@@ -56,8 +56,6 @@ __FBSDID("$FreeBSD$");
 #include <netinet/cc/cc.h>
 #include <netinet/cc/cc_module.h>
 
-#define	CAST_PTR_INT(X)	(*((int*)(X)))
-
 #define MAX_ALPHA_VALUE 1024
 static VNET_DEFINE(uint32_t, dctcp_alpha) = 0;
 #define V_dctcp_alpha	    VNET(dctcp_alpha)
@@ -401,7 +399,7 @@ dctcp_alpha_handler(SYSCTL_HANDLER_ARGS)
 	new = V_dctcp_alpha;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) > 1)
+		if (new > 1)
 			error = EINVAL;
 		else {
 			if (new > MAX_ALPHA_VALUE)
@@ -423,7 +421,7 @@ dctcp_shift_g_handler(SYSCTL_HANDLER_ARGS)
 	new = V_dctcp_shift_g;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) > 1)
+		if (new > 1)
 			error = EINVAL;
 		else
 			V_dctcp_shift_g = new;
@@ -441,7 +439,7 @@ dctcp_slowstart_handler(SYSCTL_HANDLER_ARGS)
 	new = V_dctcp_slowstart;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) > 1)
+		if (new > 1)
 			error = EINVAL;
 		else
 			V_dctcp_slowstart = new;

diff --git a/sys/netinet/cc/cc_hd.c b/sys/netinet/cc/cc_hd.c
@@ -77,8 +77,6 @@ __FBSDID("$FreeBSD$");
 
 #include <netinet/khelp/h_ertt.h>
 
-#define	CAST_PTR_INT(X)	(*((int*)(X)))
-
 /* Largest possible number returned by random(). */
 #define	RANDOM_MAX	INT_MAX
 
@@ -186,8 +184,7 @@ hd_pmax_handler(SYSCTL_HANDLER_ARGS)
 	new = V_hd_pmax;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) == 0 ||
-		    CAST_PTR_INT(req->newptr) > 100)
+		if (new == 0 || new > 100)
 			error = EINVAL;
 		else
 			V_hd_pmax = new;
@@ -205,7 +202,7 @@ hd_qmin_handler(SYSCTL_HANDLER_ARGS)
 	new = V_hd_qmin;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) > V_hd_qthresh)
+		if (new > V_hd_qthresh)
 			error = EINVAL;
 		else
 			V_hd_qmin = new;
@@ -223,8 +220,7 @@ hd_qthresh_handler(SYSCTL_HANDLER_ARGS)
 	new = V_hd_qthresh;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) < 1 ||
-		    CAST_PTR_INT(req->newptr) < V_hd_qmin)
+		if (new == 0 || new < V_hd_qmin)
 			error = EINVAL;
 		else
 			V_hd_qthresh = new;

diff --git a/sys/netinet/cc/cc_vegas.c b/sys/netinet/cc/cc_vegas.c
@@ -77,8 +77,6 @@ __FBSDID("$FreeBSD$");
 
 #include <netinet/khelp/h_ertt.h>
 
-#define	CAST_PTR_INT(X)	(*((int*)(X)))
-
 /*
  * Private signal type for rate based congestion signal.
  * See <netinet/cc.h> for appropriate bit-range to use for private signals.
@@ -260,8 +258,7 @@ vegas_alpha_handler(SYSCTL_HANDLER_ARGS)
 	new = V_vegas_alpha;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) < 1 ||
-		    CAST_PTR_INT(req->newptr) > V_vegas_beta)
+		if (new == 0 || new > V_vegas_beta)
 			error = EINVAL;
 		else
 			V_vegas_alpha = new;
@@ -279,8 +276,7 @@ vegas_beta_handler(SYSCTL_HANDLER_ARGS)
 	new = V_vegas_beta;
 	error = sysctl_handle_int(oidp, &new, 0, req);
 	if (error == 0 && req->newptr != NULL) {
-		if (CAST_PTR_INT(req->newptr) < 1 ||
-		    CAST_PTR_INT(req->newptr) < V_vegas_alpha)
+		if (new == 0 || new < V_vegas_alpha)
 			 error = EINVAL;
 		else
 			V_vegas_beta = new;

diff --git a/sys/netinet/siftr.c b/sys/netinet/siftr.c
@@ -150,8 +150,6 @@ __FBSDID("$FreeBSD$");
 #endif
 
 /* useful macros */
-#define CAST_PTR_INT(X) (*((int*)(X)))
-
 #define UPPER_SHORT(X)	(((X) & 0xFFFF0000) >> 16)
 #define LOWER_SHORT(X)	((X) & 0x0000FFFF)
 
@@ -1440,22 +1438,22 @@ siftr_manage_ops(uint8_t action)
 static int
 siftr_sysctl_enabled_handler(SYSCTL_HANDLER_ARGS)
 {
-	if (req->newptr == NULL)
-		goto skip;
-
-	/* If the value passed in isn't 0 or 1, return an error. */
-	if (CAST_PTR_INT(req->newptr) != 0 && CAST_PTR_INT(req->newptr) != 1)
-		return (1);
-
-	/* If we are changing state (0 to 1 or 1 to 0). */
-	if (CAST_PTR_INT(req->newptr) != siftr_enabled )
-		if (siftr_manage_ops(CAST_PTR_INT(req->newptr))) {
-			siftr_manage_ops(SIFTR_DISABLE);
-			return (1);
+	int error;
+	uint32_t new;
+
+	new = siftr_enabled;
+	error = sysctl_handle_int(oidp, &new, 0, req);
+	if (error != 0 && req->newptr != NULL) {
+		if (new > 1)
+			return (EINVAL);
+		else if (new != siftr_enabled) {
+			error = siftr_manage_ops(new);
+			if (error != 0)
+				siftr_manage_ops(SIFTR_DISABLE);
 		}
+	}
 
-skip:
-	return (sysctl_handle_int(oidp, arg1, arg2, req));
+	return (error);
 }