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Subject[PATCH] mmaper_kern.c fixes [buffer overruns]
	* copy_from_user() can fail; ->write() must check its return
value.
* severe buffer overruns both in ->read() and ->write() - lseek
to the end (i.e. to mmapper_size) and
if(count + *ppos > mmapper_size)
count = count + *ppos - mmapper_size;
will do absolutely nothing. Then it will call
copy_to_user(buf,&v_buf[*ppos],count);
with obvious results (similar for ->write()).
Fixed by turning read to simple_read_from_buffer() and by doing
normal limiting of count in ->write().
* gratitious lock_kernel() in ->mmap() - it's useless there.
* lots of gratitious includes.

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
----
diff -urN RC13-rc7-base/arch/um/drivers/mmapper_kern.c current/arch/um/drivers/mmapper_kern.c
--- RC13-rc7-base/arch/um/drivers/mmapper_kern.c 2005-06-17 15:48:29.000000000 -0400
+++ current/arch/um/drivers/mmapper_kern.c 2005-08-27 01:25:20.000000000 -0400
@@ -9,19 +9,11 @@
*
*/

-#include <linux/types.h>
-#include <linux/kdev_t.h>
-#include <linux/time.h>
-#include <linux/devfs_fs_kernel.h>
+#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
-#include <linux/slab.h>
-#include <linux/init.h>
-#include <linux/smp_lock.h>
#include <linux/miscdevice.h>
#include <asm/uaccess.h>
-#include <asm/irq.h>
-#include <asm/pgtable.h>
#include "mem_user.h"
#include "user_util.h"

@@ -31,35 +23,22 @@
static char *v_buf = NULL;

static ssize_t
-mmapper_read(struct file *file, char *buf, size_t count, loff_t *ppos)
+mmapper_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
- if(*ppos > mmapper_size)
- return -EINVAL;
-
- if(count + *ppos > mmapper_size)
- count = count + *ppos - mmapper_size;
-
- if(count < 0)
- return -EINVAL;
-
- copy_to_user(buf,&v_buf[*ppos],count);
-
- return count;
+ return simple_read_from_buffer(buf, count, ppos, v_buf, mmapper_size);
}

static ssize_t
-mmapper_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
+mmapper_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
- if(*ppos > mmapper_size)
+ if (*ppos > mmapper_size)
return -EINVAL;

- if(count + *ppos > mmapper_size)
- count = count + *ppos - mmapper_size;
-
- if(count < 0)
- return -EINVAL;
+ if (count > mmapper_size - *ppos)
+ count = mmapper_size - *ppos;

- copy_from_user(&v_buf[*ppos],buf,count);
+ if (copy_from_user(&v_buf[*ppos], buf, count))
+ return -EFAULT;

return count;
}
@@ -77,7 +56,6 @@
int ret = -EINVAL;
int size;

- lock_kernel();
if (vma->vm_pgoff != 0)
goto out;

@@ -92,7 +70,6 @@
goto out;
ret = 0;
out:
- unlock_kernel();
return ret;
}

-
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