mbind(): fix leak of never putback pages
KOSAKI Motohiro [Mon, 26 Oct 2009 23:49:58 +0000 (16:49 -0700)]
If mbind() receives an invalid address, do_mbind leaks a page.  The
following test program detects this leak.

This patch fixes it.

migrate_efault.c
=======================================
 #include <numaif.h>
 #include <numa.h>
 #include <sys/mman.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <stdlib.h>
 #include <string.h>

static unsigned long pagesize;

static void* make_hole_mapping(void)
{

void* addr;

addr = mmap(NULL, pagesize*3, PROT_READ|PROT_WRITE,
    MAP_ANON|MAP_PRIVATE, 0, 0);
if (addr == MAP_FAILED)
return NULL;

/* make page populate */
memset(addr, 0, pagesize*3);

/* make memory hole */
munmap(addr+pagesize, pagesize);

return addr;
}

int main(int argc, char** argv)
{
void* addr;
int ch;
int node;
struct bitmask *nmask = numa_allocate_nodemask();
int err;
int node_set = 0;

while ((ch = getopt(argc, argv, "n:")) != -1){
switch (ch){
case 'n':
node = strtol(optarg, NULL, 0);
numa_bitmask_setbit(nmask, node);
node_set = 1;
break;
default:
;
}
}
argc -= optind;
argv += optind;

if (!node_set)
numa_bitmask_setbit(nmask, 0);

pagesize = getpagesize();

addr = make_hole_mapping();

err = mbind(addr, pagesize*3, MPOL_BIND, nmask->maskp, nmask->size, MPOL_MF_MOVE_ALL);
if (err)
perror("mbind ");

return 0;
}
=======================================

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

index 7dd9d9f..d49956d 100644 (file)
@@ -1058,7 +1058,8 @@ static long do_mbind(unsigned long start, unsigned long len,
 
                if (!err && nr_failed && (flags & MPOL_MF_STRICT))
                        err = -EIO;
-       }
+       } else
+               putback_lru_pages(&pagelist);
 
        up_write(&mm->mmap_sem);
        mpol_put(new);