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Subject[PATCH] misc: sgi-gru: Convert from atomic_t to refcount_t on gru_thread_state->ts_refcnt
Date
refcount_t type and corresponding API can protect refcounters from
accidental underflow and overflow and further use-after-free situations.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
drivers/misc/sgi-gru/grumain.c | 6 +++---
drivers/misc/sgi-gru/grutables.h | 3 ++-
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index 40ac59dd018c..9afda47efbf2 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -282,7 +282,7 @@ static void gru_unload_mm_tracker(struct gru_state *gru,
*/
void gts_drop(struct gru_thread_state *gts)
{
- if (gts && atomic_dec_return(&gts->ts_refcnt) == 0) {
+ if (gts && refcount_dec_and_test(&gts->ts_refcnt)) {
if (gts->ts_gms)
gru_drop_mmu_notifier(gts->ts_gms);
kfree(gts);
@@ -323,7 +323,7 @@ struct gru_thread_state *gru_alloc_gts(struct vm_area_struct *vma,

STAT(gts_alloc);
memset(gts, 0, sizeof(struct gru_thread_state)); /* zero out header */
- atomic_set(&gts->ts_refcnt, 1);
+ refcount_set(&gts->ts_refcnt, 1);
mutex_init(&gts->ts_ctxlock);
gts->ts_cbr_au_count = cbr_au_count;
gts->ts_dsr_au_count = dsr_au_count;
@@ -888,7 +888,7 @@ struct gru_state *gru_assign_gru_context(struct gru_thread_state *gts)
gts->ts_gru = gru;
gts->ts_blade = gru->gs_blade_id;
gts->ts_ctxnum = gru_assign_context_number(gru);
- atomic_inc(&gts->ts_refcnt);
+ refcount_inc(&gts->ts_refcnt);
gru->gs_gts[gts->ts_ctxnum] = gts;
spin_unlock(&gru->gs_lock);

diff --git a/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h
index 5ce8f3081e96..e4c067c61251 100644
--- a/drivers/misc/sgi-gru/grutables.h
+++ b/drivers/misc/sgi-gru/grutables.h
@@ -129,6 +129,7 @@
*
*/

+#include <linux/refcount.h>
#include <linux/rmap.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
@@ -358,7 +359,7 @@ struct gru_thread_state {
enabled */
int ts_ctxnum; /* context number where the
context is loaded */
- atomic_t ts_refcnt; /* reference count GTS */
+ refcount_t ts_refcnt; /* reference count GTS */
unsigned char ts_dsr_au_count;/* Number of DSR resources
required for contest */
unsigned char ts_cbr_au_count;/* Number of CBR resources
--
2.7.4
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