make /dev/kmem a config option
Make /dev/kmem a config option; /dev/kmem is VERY rarely used, and when
used, it's generally for no good (rootkits tend to be the most common
users). With this config option, users have the choice to disable
/dev/kmem, saving some size as well.
A patch to disable /dev/kmem has been in the Fedora and RHEL kernels for
4+ years now without any known problems or legit users of /dev/kmem.
[akpm@linux-foundation.org: make CONFIG_DEVKMEM default to y]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index e83623e..934ffaf 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -364,6 +364,7 @@
return 0;
}
+#ifdef CONFIG_DEVKMEM
static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
{
unsigned long pfn;
@@ -384,6 +385,7 @@
vma->vm_pgoff = pfn;
return mmap_mem(file, vma);
}
+#endif
#ifdef CONFIG_CRASH_DUMP
/*
@@ -422,6 +424,7 @@
extern long vread(char *buf, char *addr, unsigned long count);
extern long vwrite(char *buf, char *addr, unsigned long count);
+#ifdef CONFIG_DEVKMEM
/*
* This function reads the *virtual* memory as seen by the kernel.
*/
@@ -626,6 +629,7 @@
*ppos = p;
return virtr + wrote;
}
+#endif
#ifdef CONFIG_DEVPORT
static ssize_t read_port(struct file * file, char __user * buf,
@@ -803,6 +807,7 @@
.get_unmapped_area = get_unmapped_area_mem,
};
+#ifdef CONFIG_DEVKMEM
static const struct file_operations kmem_fops = {
.llseek = memory_lseek,
.read = read_kmem,
@@ -811,6 +816,7 @@
.open = open_kmem,
.get_unmapped_area = get_unmapped_area_mem,
};
+#endif
static const struct file_operations null_fops = {
.llseek = null_lseek,
@@ -889,11 +895,13 @@
filp->f_mapping->backing_dev_info =
&directly_mappable_cdev_bdi;
break;
+#ifdef CONFIG_DEVKMEM
case 2:
filp->f_op = &kmem_fops;
filp->f_mapping->backing_dev_info =
&directly_mappable_cdev_bdi;
break;
+#endif
case 3:
filp->f_op = &null_fops;
break;
@@ -942,7 +950,9 @@
const struct file_operations *fops;
} devlist[] = { /* list of minor devices */
{1, "mem", S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
+#ifdef CONFIG_DEVKMEM
{2, "kmem", S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
+#endif
{3, "null", S_IRUGO | S_IWUGO, &null_fops},
#ifdef CONFIG_DEVPORT
{4, "port", S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},