ax25: unsigned cannot be less than 0 in ax25_ctl_ioctl()

PATCH Applied Roel Kluin 4 participants 8 messages Oct 10, 2009 – Oct 30, 2009

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Roel Kluin

author

2009-10-10 21:22 UTC #0 lore raw

PATCH 1/1 ax25: unsigned cannot be less than 0 in ax25_ctl_ioctl()

struct ax25_ctl_struct member `arg' is unsigned and cannot be less than 0.

Signed-off-by Roel Kluin <[email protected]>

---
If the ax25_ctl.arg limit is known to be lower, please suggest other values.

net/ax25/af_ax25.c +4 -4

index f454607..0d99704 100644
@@ -398,14 +398,14 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 		break;
 
 	case AX25_T1:
-		if (ax25_ctl.arg < 1)
+		if (ax25_ctl.arg < 1 || ax25_ctl.arg * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->rtt = (ax25_ctl.arg * HZ) / 2;
 		ax25->t1  = ax25_ctl.arg * HZ;
 		break;
 
 	case AX25_T2:
-		if (ax25_ctl.arg < 1)
+		if (ax25_ctl.arg < 1 || ax25_ctl.arg * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->t2 = ax25_ctl.arg * HZ;
 		break;

@@ -418,13 +418,13 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 		break;
 
 	case AX25_T3:
-		if (ax25_ctl.arg < 0)
+		if (ax25_ctl.arg * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->t3 = ax25_ctl.arg * HZ;
 		break;
 
 	case AX25_IDLE:
-		if (ax25_ctl.arg < 0)
+		if (ax25_ctl.arg * 60 * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->idle = ax25_ctl.arg * 60 * HZ;
 		break;

walter harms

2009-10-12 15:37 UTC #1 lore raw

what is about something like:

tmp_arg=ax25_ctl.arg * HZ;

if (arg == 0 || arg > ULONG_MAX )

		goto einval_put;

re,
wh

Quoted 50 lines · Roel Kluin

struct ax25_ctl_struct member `arg' is unsigned and cannot be less than 0.

Signed-off-by Roel Kluin <[email protected]>

---
If the ax25_ctl.arg limit is known to be lower, please suggest other values.

net/ax25/af_ax25.c +4 -5

index f454607..0d99704 100644
@@ -398,14 +398,14 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 		break;
 
 	case AX25_T1:
-		if (ax25_ctl.arg < 1)
+		if (ax25_ctl.arg < 1 || ax25_ctl.arg * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->rtt = (ax25_ctl.arg * HZ) / 2;
 		ax25->t1  = ax25_ctl.arg * HZ;
 		break;
 
 	case AX25_T2:
-		if (ax25_ctl.arg < 1)
+		if (ax25_ctl.arg < 1 || ax25_ctl.arg * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->t2 = ax25_ctl.arg * HZ;
 		break;

@@ -418,13 +418,13 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 		break;
 
 	case AX25_T3:
-		if (ax25_ctl.arg < 0)
+		if (ax25_ctl.arg * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->t3 = ax25_ctl.arg * HZ;
 		break;
 
 	case AX25_IDLE:
-		if (ax25_ctl.arg < 0)
+		if (ax25_ctl.arg * 60 * HZ > ULONG_MAX)
 			goto einval_put;
 		ax25->idle = ax25_ctl.arg * 60 * HZ;
 		break;
--

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Roel Kluin

author

2009-10-12 19:02 UTC #2 lore raw

struct ax25_ctl_struct member `arg' is unsigned and cannot be less than 0.

Signed-off-by Roel Kluin <[email protected]>

---

Quoted 5 lines

Quoted 2 lines
If the ax25_ctl.arg limit is known to be lower, please suggest other values.
what is about something like:

Quoted 7 lines

tmp_arg=ax25_ctl.arg * HZ;
if (arg == 0 || arg > ULONG_MAX )
		goto einval_put;
re,
wh

I'm not sure, I think this would only work if we made `arg' an unsigned long long.

How about this?

net/ax25/af_ax25.c +3 -4

index f454607..20ff0f3 100644
@@ -369,6 +369,9 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 	if (ax25_ctl.digi_count > AX25_MAX_DIGIS)
 		return -EINVAL;
 
+	if (ax25_ctl.arg * HZ > ULONG_MAX && ax25_ctl.cmd != AX25_KILL)
+		return -EINVAL;
+
 	digi.ndigi = ax25_ctl.digi_count;
 	for (k = 0; k < digi.ndigi; k++)
 		digi.calls[k] = ax25_ctl.digi_addr[k];

@@ -418,14 +421,10 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 		break;
 
 	case AX25_T3:
-		if (ax25_ctl.arg < 0)
-			goto einval_put;
 		ax25->t3 = ax25_ctl.arg * HZ;
 		break;
 
 	case AX25_IDLE:
-		if (ax25_ctl.arg < 0)
-			goto einval_put;
 		ax25->idle = ax25_ctl.arg * 60 * HZ;
 		break;

walter harms

2009-10-13 09:48 UTC #4 lore raw

Quoted 15 lines · Kevin Dawson

Quoted 7 lines · Roel Kluin
Quoted 4 lines
tmp_arg=ax25_ctl.arg * HZ;
  if (arg == 0 || arg >  ULONG_MAX )
        goto einval_put;
I'm not sure, I think this would only work if we made `arg' an unsigned long long.
That depends on the possible values of ax25_ctl.arg.
net/ax25/af_ax25.c static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg) · line 373
Quoted 2 lines
net/ax25/af_ax25.c +2 -0
+    if (ax25_ctl.arg * HZ > ULONG_MAX && ax25_ctl.cmd != AX25_KILL)
+        return -EINVAL;

Quoted 7 lines

Why the need to change arg before comparing it with a constant? Let the compiler do the work:
    if (ax25_ctl.arg > ULONG_MAX / HZ && ...
Kevin

i like this because it prevents a wrap around for stupid ax25_ctl.arg values but will not help when ax25_ctl.arg * HZ is used later. NTL i think HZ does not need to be constant these days but i am not an expert on that area.

re,
wh

Kevin Dawson

2009-10-13 21:50 UTC #5 lore raw

Quoted 8 lines · walter harms

Quoted 2 lines · Kevin Dawson
    if (ax25_ctl.arg > ULONG_MAX / HZ && ...
i like this because it prevents a wrap around for stupid ax25_ctl.arg values but will not help when ax25_ctl.arg * HZ is used later. NTL i think HZ does not need to be constant these days but i am not an expert on that area.

I don't have a kernel source tree at the moment, so I haven't seen where it's used, but the same size-limiting principle using divisions would apply whether you have constants, variables or function calls.

If ax25_ctl.arg * HZ is used later, one should arrange that the thread won't get that far if it has already been deemed an excessive value.

Kevin

Roel Kluin

author

2009-10-14 15:17 UTC #6 lore raw

In reply to Kevin Dawson

struct ax25_ctl_struct member `arg' is unsigned and cannot be less than 0.

Signed-off-by Roel Kluin <[email protected]>

---
Op 12-10-09 23:58, Kevin Dawson schreef:

Quoted 10 lines

Quoted 7 lines
Quoted 4 lines
tmp_arg=ax25_ctl.arg * HZ;
  if (arg == 0 || arg >  ULONG_MAX )
        goto einval_put;
I'm not sure, I think this would only work if we made `arg' an unsigned long long.
That depends on the possible values of ax25_ctl.arg.

Quoted 7 lines

Review
Quoted 2 lines
(quoted diff) +2 -0
+    if (ax25_ctl.arg * HZ > ULONG_MAX && ax25_ctl.cmd != AX25_KILL)
+        return -EINVAL;
Why the need to change arg before comparing it with a constant? Let the compiler do the work:
    if (ax25_ctl.arg > ULONG_MAX / HZ && ...

Ok, How about this then?

net/ax25/af_ax25.c +3 -4

index f454607..d923ac4 100644
@@ -369,6 +369,9 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 	if (ax25_ctl.digi_count > AX25_MAX_DIGIS)
 		return -EINVAL;
 
+	if (ax25_ctl.arg > ULONG_MAX / HZ && ax25_ctl.cmd != AX25_KILL)
+		return -EINVAL;
+
 	digi.ndigi = ax25_ctl.digi_count;
 	for (k = 0; k < digi.ndigi; k++)
 		digi.calls[k] = ax25_ctl.digi_addr[k];

@@ -418,14 +421,10 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
 		break;
 
 	case AX25_T3:
-		if (ax25_ctl.arg < 0)
-			goto einval_put;
 		ax25->t3 = ax25_ctl.arg * HZ;
 		break;
 
 	case AX25_IDLE:
-		if (ax25_ctl.arg < 0)
-			goto einval_put;
 		ax25->idle = ax25_ctl.arg * 60 * HZ;
 		break;

David Miller

maintainer Applied

2009-10-30 06:06 UTC #7 lore raw

From: Roel Kluin <[email protected]>
Date: Wed, 14 Oct 2009 17:26:30 +0200

Quoted 4 lines

struct ax25_ctl_struct member `arg' is unsigned and cannot be less than 0.
Signed-off-by Roel Kluin <[email protected]>

Applied to net-next-2.6