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Commit 3434caec authored by Chuhong Yuan's avatar Chuhong Yuan Committed by Vasily Gorbik
Browse files

s390/extmem: use refcount_t for refcount 

Reference counters are preferred to use refcount_t instead of
atomic_t.
This is because the implementation of refcount_t can prevent
overflows and detect possible use-after-free.
So convert atomic_t ref counters to refcount_t.

Link: http://lkml.kernel.org/r/20190808071817.6595-1-hslester96@gmail.com


Signed-off-by: default avatarChuhong Yuan <hslester96@gmail.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent c4c37723

arch/s390/mm/extmem.c

+6 −5
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/memblock.h>

#include <linux/ctype.h>

#include <linux/ioport.h>

#include <linux/refcount.h>

#include <asm/diag.h>

#include <asm/page.h>

#include <asm/pgtable.h>
@@ -64,7 +65,7 @@ struct dcss_segment { 
	char res_name[16];

	unsigned long start_addr;

	unsigned long end;

	atomic_t ref_count;

	refcount_t ref_count;

	int do_nonshared;

	unsigned int vm_segtype;

	struct qrange range[6];
@@ -362,7 +363,7 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long 
	seg->start_addr = start_addr;

	seg->end = end_addr;

	seg->do_nonshared = do_nonshared;

	atomic_set(&seg->ref_count, 1);

	refcount_set(&seg->ref_count, 1);

	list_add(&seg->list, &dcss_list);

	*addr = seg->start_addr;

	*end  = seg->end;
@@ -422,7 +423,7 @@ segment_load (char *name, int do_nonshared, unsigned long *addr, 
		rc = __segment_load (name, do_nonshared, addr, end);

	else {

		if (do_nonshared == seg->do_nonshared) {

			atomic_inc(&seg->ref_count);

			refcount_inc(&seg->ref_count);

			*addr = seg->start_addr;

			*end  = seg->end;

			rc    = seg->vm_segtype;
@@ -468,7 +469,7 @@ segment_modify_shared (char *name, int do_nonshared) 
		rc = 0;

		goto out_unlock;

	}

	if (atomic_read (&seg->ref_count) != 1) {

	if (refcount_read(&seg->ref_count) != 1) {

		pr_warn("DCSS %s is in use and cannot be reloaded\n", name);

		rc = -EAGAIN;

		goto out_unlock;
@@ -544,7 +545,7 @@ segment_unload(char *name) 
		pr_err("Unloading unknown DCSS %s failed\n", name);

		goto out_unlock;

	}

	if (atomic_dec_return(&seg->ref_count) != 0)

	if (!refcount_dec_and_test(&seg->ref_count))

		goto out_unlock;

	release_resource(seg->res);

	kfree(seg->res);