Re: [PATCH] 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 <redacted>
---

quoted

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

what is about something like:

 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?

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index f454607..20ff0f3 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c

@@ -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;
 

Roel Kluin wrote:

quoted

 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.

+	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 && ...

Kevin

Kevin Dawson schrieb:

Roel Kluin wrote:

quoted

quoted

 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

+    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 && ...

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

walter harms wrote:

Kevin Dawson schrieb:

quoted

    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

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

Signed-off-by: Roel Kluin <redacted>
---
Op 12-10-09 23:58, Kevin Dawson schreef:

quoted

quoted

 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

+    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?

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index f454607..d923ac4 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c

@@ -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;
 

From: Roel Kluin <redacted>
Date: Wed, 14 Oct 2009 17:26:30 +0200

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

Signed-off-by: Roel Kluin <redacted>

Applied to net-next-2.6