From: Anton Volkov <avolkov@ispras.ru>
To: isdn@linux-pingi.de
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
ldv-project@linuxtesting.org, khoroshilov@ispras.ru
Subject: [PATCH] hysdn: fix to a race condition in put_log_buffer
Date: Fri, 28 Jul 2017 17:53:51 +0300 [thread overview]
Message-ID: <fd42b4de-416a-4e1b-046a-378aa66f7486@ispras.ru> (raw)
In-Reply-To: <2f35ddaf-88d9-e848-f83b-3001b36b2883@linux-pingi.de>
The synchronization type that was used earlier to guard the loop that
deletes unused log buffers may have lead to a situation that prevents
any thread from going through the loop.
The patch deletes previously used synchronization mechanism and moves
the loop under the spin_lock so the similar cases won't be feasible in
the future.
Found by by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Anton Volkov <avolkov@ispras.ru>
---
drivers/isdn/hysdn/hysdn_proclog.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)
diff --git a/drivers/isdn/hysdn/hysdn_proclog.c
b/drivers/isdn/hysdn/hysdn_proclog.c
index 7b5fd8fb1761..b152c6ca444b 100644
--- a/drivers/isdn/hysdn/hysdn_proclog.c
+++ b/drivers/isdn/hysdn/hysdn_proclog.c
@@ -44,7 +44,6 @@ struct procdata {
char log_name[15]; /* log filename */
struct log_data *log_head, *log_tail; /* head and tail for queue */
int if_used; /* open count for interface */
- int volatile del_lock; /* lock for delete operations */
unsigned char logtmp[LOG_MAX_LINELEN];
wait_queue_head_t rd_queue;
};
@@ -102,7 +101,6 @@ put_log_buffer(hysdn_card *card, char *cp)
{
struct log_data *ib;
struct procdata *pd = card->proclog;
- int i;
unsigned long flags;
if (!pd)
@@ -126,21 +124,20 @@ put_log_buffer(hysdn_card *card, char *cp)
else
pd->log_tail->next = ib; /* follows existing messages */
pd->log_tail = ib; /* new tail */
- i = pd->del_lock++; /* get lock state */
- spin_unlock_irqrestore(&card->hysdn_lock, flags);
/* delete old entrys */
- if (!i)
- while (pd->log_head->next) {
- if ((pd->log_head->usage_cnt <= 0) &&
- (pd->log_head->next->usage_cnt <= 0)) {
- ib = pd->log_head;
- pd->log_head = pd->log_head->next;
- kfree(ib);
- } else
- break;
- } /* pd->log_head->next */
- pd->del_lock--; /* release lock level */
+ while (pd->log_head->next) {
+ if ((pd->log_head->usage_cnt <= 0) &&
+ (pd->log_head->next->usage_cnt <= 0)) {
+ ib = pd->log_head;
+ pd->log_head = pd->log_head->next;
+ kfree(ib);
+ } else
+ break;
+ } /* pd->log_head->next */
+
+ spin_unlock_irqrestore(&card->hysdn_lock, flags);
+
wake_up_interruptible(&(pd->rd_queue)); /* announce new entry */
} /* put_log_buffer */
--
2.11.0
next prev parent reply other threads:[~2017-07-28 14:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-27 16:19 Possible race in hysdn.ko Anton Volkov
2017-07-28 4:46 ` isdn
2017-07-28 14:53 ` Anton Volkov [this message]
2017-08-01 0:22 ` [PATCH] hysdn: fix to a race condition in put_log_buffer David Miller
2017-08-03 11:33 ` Anton Volkov
2017-08-03 12:03 ` Sergei Shtylyov
2017-08-07 12:54 ` [PATCH v2] " Anton Volkov
2017-08-07 18:25 ` David Miller
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