Re: [Patch 0/2] powerpc: avoid userspace poking to legacy ioports

Hi Ben,

On Thu, 14 Feb 2008 07:42:54 +1100, Benjamin Herrenschmidt wrote:

On Wed, 2008-02-13 at 18:35 +0100, Christian Krafft wrote:

quoted

sensors_detect crashes kernel on PowerPC, as it pokes directly to memory.

For the records, sensors-detect accesses I/O ports, not memory.

quoted

This patch adds a check_legacy_ioports to read_port and write_port.
It will now return ENXIO, instead of oopsing.

Signed-off-by: Christian Krafft <redacted>

The problem is that this prevents using /proc/ioports to access PCI
IO space, which might be useful.

Maybe Christian's patch can be improved to not do the check on these?
As long as /dev/port exists, it seems reasonable that the kernel should
behave, no matter what I/O ports are accessed from user-space.

I hate that sensors_detect.. or for that matter any other userland code
that pokes random ports like that. It should die.

What do you propose as a replacement?

And how is userland code poking at random ports different from kernel
code poking at random ports? We could move sensors-detect inside the
kernel (and I have some plan to do that) but I fail to see how this
would solve this particular problem.

quoted

Index: linux.git/drivers/char/mem.c
===================================================================

--- linux.git.orig/drivers/char/mem.c
+++ linux.git/drivers/char/mem.c

@@ -566,8 +566,13 @@ static ssize_t read_port(struct file * f
 	char __user *tmp = buf;
 
 	if (!access_ok(VERIFY_WRITE, buf, count))
-		return -EFAULT; 
+		return -EFAULT;
+
 	while (count-- > 0 && i < 65536) {
+#ifdef CONFIG_PPC_MERGE
+		if (check_legacy_ioport(i))
+			return -ENXIO;
+#endif
 		if (__put_user(inb(i),tmp) < 0) 
 			return -EFAULT;  
 		i++;

@@ -585,6 +590,7 @@ static ssize_t write_port(struct file * 
 
 	if (!access_ok(VERIFY_READ,buf,count))
 		return -EFAULT;
+
 	while (count-- > 0 && i < 65536) {
 		char c;
 		if (__get_user(c, tmp)) {

@@ -592,6 +598,10 @@ static ssize_t write_port(struct file * 
 				break;
 			return -EFAULT; 
 		}
+#ifdef CONFIG_PPC_MERGE
+		if (check_legacy_ioport(i))
+			return -ENXIO;
+#endif
 		outb(c,i);
 		i++;
 		tmp++;

-- 
Jean Delvare