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Commit f7d88d24 authored by Elena Reshetova's avatar Elena Reshetova Committed by Greg Kroah-Hartman
Browse files

drivers, char: convert vma_data.refcnt from atomic_t to refcount_t 



refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 132c93d4

drivers/char/mspec.c

+5 −4
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#include <linux/string.h>

#include <linux/slab.h>

#include <linux/numa.h>

#include <linux/refcount.h>

#include <asm/page.h>

#include <asm/pgtable.h>

#include <linux/atomic.h>
@@ -89,7 +90,7 @@ static int is_sn2; 
 * protect in fork case where multiple tasks share the vma_data.

 */

struct vma_data {

	atomic_t refcnt;	/* Number of vmas sharing the data. */

	refcount_t refcnt;	/* Number of vmas sharing the data. */

	spinlock_t lock;	/* Serialize access to this structure. */

	int count;		/* Number of pages allocated. */

	enum mspec_page_type type; /* Type of pages allocated. */
@@ -144,7 +145,7 @@ mspec_open(struct vm_area_struct *vma) 
	struct vma_data *vdata;



	vdata = vma->vm_private_data;

	atomic_inc(&vdata->refcnt);

	refcount_inc(&vdata->refcnt);

}



/*
@@ -162,7 +163,7 @@ mspec_close(struct vm_area_struct *vma) 


	vdata = vma->vm_private_data;



	if (!atomic_dec_and_test(&vdata->refcnt))

	if (!refcount_dec_and_test(&vdata->refcnt))

		return;



	last_index = (vdata->vm_end - vdata->vm_start) >> PAGE_SHIFT;
@@ -274,7 +275,7 @@ mspec_mmap(struct file *file, struct vm_area_struct *vma, 
	vdata->vm_end = vma->vm_end;

	vdata->type = type;

	spin_lock_init(&vdata->lock);

	atomic_set(&vdata->refcnt, 1);

	refcount_set(&vdata->refcnt, 1);

	vma->vm_private_data = vdata;



	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;