FAILED: patch "[PATCH] batman-adv: tp_meter: fix race condition in send error" failed to apply to 5.10-stable tree

PATCH New [email protected] 2 participants 2 messages May 28 – May 29

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author maintainer

2026-05-28 11:56 UTC #0 lore raw

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 71dce47f0758537fff78fddb5fb0d4632d29b29f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026052834-wad-startle-2b67@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 71dce47f0758537fff78fddb5fb0d4632d29b29f Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <[email protected]>
Date: Wed, 13 May 2026 23:38:54 +0200
Subject: [PATCH] batman-adv: tp_meter: fix race condition in send error
reporting

batadv_tp_sender_shutdown() previously used two separate variables to track session state: sending (an atomic flag indicating whether the session was active) and reason (a plain enum storing the stop reason). This introduced a race window between the two writes: after sending was cleared to 0, batadv_tp_send() could observe the stopped state and call batadv_tp_sender_end() before reason was written, causing the wrong stop reason to be reported to the caller.

Fix this by consolidating both variables into a single atomic send_result, which holds 0 while the session is running and the stop reason once it ends.

Cc [email protected]

Fixes 33a3bb4a3345 ("batman-adv: throughput meter implementation")

Signed-off-by Sven Eckelmann <[email protected]>

net/batman-adv/tp_meter.c +25 ~~-15~~

index 1fd1526059d8..3ce6d9b2c9f3 100644
@@ -413,11 +413,14 @@ static void batadv_tp_sender_cleanup(struct batadv_tp_vars *tp_vars)
 static void batadv_tp_sender_end(struct batadv_priv *bat_priv,
 				 struct batadv_tp_vars *tp_vars)
 {
+	enum batadv_tp_meter_reason reason;
 	u32 session_cookie;
 
+	reason = atomic_read(&tp_vars->send_result);
+
 	batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
 		   "Test towards %pM finished..shutting down (reason=%d)\n",
-		   tp_vars->other_end, tp_vars->reason);
+		   tp_vars->other_end, reason);
 
 	batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
 		   "Last timing stats: SRTT=%ums RTTVAR=%ums RTO=%ums\n",

@@ -430,7 +433,7 @@ static void batadv_tp_sender_end(struct batadv_priv *bat_priv,
 	session_cookie = batadv_tp_session_cookie(tp_vars->session,
 						  tp_vars->icmp_uid);
 
-	batadv_tp_batctl_notify(tp_vars->reason,
+	batadv_tp_batctl_notify(reason,
 				tp_vars->other_end,
 				bat_priv,
 				tp_vars->start_time,

@@ -446,10 +449,18 @@ static void batadv_tp_sender_end(struct batadv_priv *bat_priv,
 static void batadv_tp_sender_shutdown(struct batadv_tp_vars *tp_vars,
 				      enum batadv_tp_meter_reason reason)
 {
-	if (atomic_xchg(&tp_vars->sending, 0) != 1)
-		return;
+	atomic_cmpxchg(&tp_vars->send_result, 0, reason);
+}
 
-	tp_vars->reason = reason;
+/**
+ * batadv_tp_sender_stopped() - check if tp session was stopped with reason
+ * @tp_vars: the private data of the current TP meter session
+ *
+ * Return: whether stop reason was found
+ */
+static bool batadv_tp_sender_stopped(struct batadv_tp_vars *tp_vars)
+{
+	return atomic_read(&tp_vars->send_result) != 0;
 }
 
 /**

@@ -479,7 +490,7 @@ static void batadv_tp_reset_sender_timer(struct batadv_tp_vars *tp_vars)
 	/* most of the time this function is invoked while normal packet
 	 * reception...
 	 */
-	if (unlikely(atomic_read(&tp_vars->sending) == 0))
+	if (unlikely(batadv_tp_sender_stopped(tp_vars)))
 		/* timer ref will be dropped in batadv_tp_sender_cleanup */
 		return;

@@ -499,7 +510,7 @@ static void batadv_tp_sender_timeout(struct timer_list *t)
 	struct batadv_tp_vars *tp_vars = timer_container_of(tp_vars, t, timer);
 	struct batadv_priv *bat_priv = tp_vars->bat_priv;
 
-	if (atomic_read(&tp_vars->sending) == 0)
+	if (batadv_tp_sender_stopped(tp_vars))
 		return;
 
 	/* if the user waited long enough...shutdown the test */

@@ -661,7 +672,7 @@ static void batadv_tp_recv_ack(struct batadv_priv *bat_priv,
 	if (unlikely(tp_vars->role != BATADV_TP_SENDER))
 		goto out;
 
-	if (unlikely(atomic_read(&tp_vars->sending) == 0))
+	if (unlikely(batadv_tp_sender_stopped(tp_vars)))
 		goto out;
 
 	/* old ACK? silently drop it.. */

@@ -827,21 +838,21 @@ static int batadv_tp_send(void *arg)
 
 	if (unlikely(tp_vars->role != BATADV_TP_SENDER)) {
 		err = BATADV_TP_REASON_DST_UNREACHABLE;
-		tp_vars->reason = err;
+		batadv_tp_sender_shutdown(tp_vars, err);
 		goto out;
 	}
 
 	orig_node = batadv_orig_hash_find(bat_priv, tp_vars->other_end);
 	if (unlikely(!orig_node)) {
 		err = BATADV_TP_REASON_DST_UNREACHABLE;
-		tp_vars->reason = err;
+		batadv_tp_sender_shutdown(tp_vars, err);
 		goto out;
 	}
 
 	primary_if = batadv_primary_if_get_selected(bat_priv);
 	if (unlikely(!primary_if)) {
 		err = BATADV_TP_REASON_DST_UNREACHABLE;
-		tp_vars->reason = err;
+		batadv_tp_sender_shutdown(tp_vars, err);
 		goto out;
 	}

@@ -860,7 +871,7 @@ static int batadv_tp_send(void *arg)
 	queue_delayed_work(batadv_event_workqueue, &tp_vars->finish_work,
 			   msecs_to_jiffies(tp_vars->test_length));
 
-	while (atomic_read(&tp_vars->sending) != 0) {
+	while (!batadv_tp_sender_stopped(tp_vars)) {
 		if (unlikely(!batadv_tp_avail(tp_vars, payload_len))) {
 			batadv_tp_wait_available(tp_vars, payload_len);
 			continue;

@@ -883,8 +894,7 @@ static int batadv_tp_send(void *arg)
 				   "Meter: %s() cannot send packets (%d)\n",
 				   __func__, err);
 			/* ensure nobody else tries to stop the thread now */
-			if (atomic_xchg(&tp_vars->sending, 0) == 1)
-				tp_vars->reason = err;
+			batadv_tp_sender_shutdown(tp_vars, err);
 			break;
 		}

@@ -1006,7 +1016,7 @@ void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
 	ether_addr_copy(tp_vars->other_end, dst);
 	kref_init(&tp_vars->refcount);
 	tp_vars->role = BATADV_TP_SENDER;
-	atomic_set(&tp_vars->sending, 1);
+	atomic_set(&tp_vars->send_result, 0);
 	memcpy(tp_vars->session, session_id, sizeof(session_id));
 	tp_vars->icmp_uid = icmp_uid;

net/batman-adv/types.h +5 -5

index c8c3e8064f00..fb0e4cb89d79 100644
@@ -1320,15 +1320,15 @@ struct batadv_tp_vars {
 	/** @role: receiver/sender modi */
 	enum batadv_tp_meter_role role;
 
-	/** @sending: sending binary semaphore: 1 if sending, 0 is not */
-	atomic_t sending;
+	/**
+	 * @send_result: 0 when sending is ongoing and otherwise
+	 * enum batadv_tp_meter_reason
+	 */
+	atomic_t send_result;
 
 	/** @receiving: receiving binary semaphore: 1 if receiving, 0 is not */
 	atomic_t receiving;
 
-	/** @reason: reason for a stopped session */
-	enum batadv_tp_meter_reason reason;
-
 	/** @finish_work: work item for the finishing procedure */
 	struct delayed_work finish_work;

Sven Eckelmann

maintainer

2026-05-29 20:14 UTC #1 lore raw

PATCH 1/1 batman-adv: tp_meter: fix race condition in send error reporting

commit 71dce47f0758537fff78fddb5fb0d4632d29b29f upstream.