[PATCH] MM, NUMA : sys_set_mempolicy() doesnt check if mode < 0

[Eric Dumazet]

MM, NUMA : sys_set_mempolicy() doesnt check if mode < 0

A kernel BUG() is triggered by a call to set_mempolicy() with a negative first argument.
This is because the mode is declared as an int, and the validity check doesnt check < 0 values.
Alternatively, mode could be declared as unsigned int or unsigned long.

Thank you
Eric
---------------------------------
Test program for x86_64:
---------------------------------
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <linux/unistd.h>

#define __NR_set_mempolicy      238
#define __sys_set_mempolicy(mode, nmask, maxnode) _syscall3(int, set_mempolicy, int, mode, unsigned long *, nmask, unsigned long, maxnode)
static __sys_set_mempolicy(mode, nmask, maxnode)

unsigned long nodes = 3;

int main()
{
int ret = set_mempolicy(-6, &nodes, 2);
printf("result=%d errno=%d\n", ret, errno);
return 0;
}


Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>

--- linux-2.6.13-rc4/mm/mempolicy.c	2005-07-29 00:44:44.000000000 +0200
+++ linux-2.6.13-rc4-ed/mm/mempolicy.c	2005-08-01 23:52:43.000000000 +0200
@@ -443,7 +443,7 @@
 	struct mempolicy *new;
 	DECLARE_BITMAP(nodes, MAX_NUMNODES);
 
-	if (mode > MPOL_MAX)
+	if ((unsigned int)mode > MPOL_MAX)
 		return -EINVAL;
 	err = get_nodes(nodes, nmask, maxnode, mode);
 	if (err)