On 10/31/2017 12:01 PM, Yisheng Xie wrote:

On 2017/10/31 17:30, Vlastimil Babka wrote:

quoted

On 10/27/2017 12:14 PM, Yisheng Xie wrote:

quoted

+	/*
+	 * When the user specified more nodes than supported just check
+	 * if the non supported part is all zero.
+	 *
+	 * If maxnode have more longs than MAX_NUMNODES, check
+	 * the bits in that area first. And then go through to
+	 * check the rest bits which equal or bigger than MAX_NUMNODES.
+	 * Otherwise, just check bits [MAX_NUMNODES, maxnode).
+	 */
 	if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
 		for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
-			unsigned long t;
 			if (get_user(t, nmask + k))
 				return -EFAULT;
 			if (k == nlongs - 1) {

@@ -1294,6 +1301,16 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
 		endmask = ~0UL;
 	}
 
+	if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) {
+		unsigned long valid_mask = endmask;
+
+		valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1);

I'm not sure if the combination with endmask works in this case:

0      BITS_PER_LONG  2xBITS_PER_LONG
|____________|____________|
       |             |
  MAX_NUMNODES      maxnode

endmask will contain bits between 0 and maxnode

In the case, BITS_TO_LONGS(maxnode) > BITS_TO_LONGS(MAX_NUMNODES), right?
And after checking BITS_PER_LONG to 2xBITS_PER_LONG，endmask will set to
"~0UL". e.g. endmask will be 0xffff ffff ffff ffff if
unsigned long is 64bit.

Then the valid_mask will just contain bits MAX_NUMNODES to BITS_PER_LONG.

Ugh, right. I missed that. This code is not simple...

Thanks
Yisheng Xie

quoted

but here we want to check bits between MAX_NUMNODES and BITS_PER_LONG
and endmask should not be mixed up with that?


Vlastimil

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