Skip to contentSkip to conversation

FAILED: patch "[PATCH] batman-adv: tp_meter: fix race condition in send error" failed to apply to 6.1-stable tree

PATCH Applied [email protected] 3 participants 5 messages May 28 – Jun 3

Subsystems (2)
Stable branch Batman advanced
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 6.1-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-6.1.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 '2026052833-easing-gerbil-ae19@gregkh' --subject-prefix 'PATCH 6.1.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;
maintainer
#1 lore raw

PATCH 1/2 batman-adv: tp_meter: fix tp_vars reference leak in receiver shutdown

commit 77098e4bea37af51d3962efa88a5af2ea5e1ac57 upstream.

The receiver shutdown timer handler, batadv_tp_receiver_shutdown(), is responsible for releasing the tp_vars reference it holds. However, the existing logic for coordinating this release with batadv_tp_stop_all() was flawed.

timer_shutdown_sync() guarantees the timer will not fire again after it returns, but it returns non-zero only when the timer was pending at the time of the call. If the timer had already expired (and batadv_tp_stop_all() would unsucessfully try to rearm itself), batadv_tp_stop_all() skips its batadv_tp_vars_put(), and batadv_tp_receiver_shutdown() fails to put its own reference as well.

Fix this by introducing a new atomic variable receiving that is set to 1 when the receiver is initialized and cleared atomically with atomic_xchg() by whichever side claims it first. Only the side that observes the transition from 1 to 0 is responsible for releasing the tp_vars timer reference, eliminating the uncertainty.

Cc [email protected]
Fixes 3d3cf6a7314a ("batman-adv: stop tp_meter sessions during mesh teardown")
Signed-off-by Sven Eckelmann <[email protected]>
---
 net/batman-adv/tp_meter.c | 13 +++++++++++--
 net/batman-adv/types.h    |  3 +++
 2 files changed, 14 insertions(+), 2 deletions(-)
net/batman-adv/tp_meter.c +11 -2
index 72652894e9d78..6cb1820fa4a4a 100644
@@ -8,6 +8,7 @@
 #include "main.h"
 
 #include <linux/atomic.h>
+#include <linux/bug.h>
 #include <linux/build_bug.h>
 #include <linux/byteorder/generic.h>
 #include <linux/cache.h>

@@ -1157,6 +1158,9 @@ static void batadv_tp_receiver_shutdown(struct timer_list *t)
 	spin_unlock_bh(&tp_vars->unacked_lock);
 
 	/* drop reference of timer */
+	if (WARN_ON(atomic_xchg(&tp_vars->receiving, 0) != 1))
+		return;
+
 	batadv_tp_vars_put(tp_vars);
 }
 

@@ -1375,6 +1379,7 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
 
 	ether_addr_copy(tp_vars->other_end, icmp->orig);
 	tp_vars->role = BATADV_TP_RECEIVER;
+	atomic_set(&tp_vars->receiving, 1);
 	memcpy(tp_vars->session, icmp->session, sizeof(tp_vars->session));
 	tp_vars->last_recv = BATADV_TP_FIRST_SEQ;
 	tp_vars->bat_priv = bat_priv;

@@ -1547,8 +1552,12 @@ void batadv_tp_stop_all(struct batadv_priv *bat_priv)
 			break;
 		case BATADV_TP_RECEIVER:
 			batadv_tp_list_detach(tp_var);
-			if (timer_shutdown_sync(&tp_var->timer))
-				batadv_tp_vars_put(tp_var);
+			timer_shutdown_sync(&tp_var->timer);
+
+			if (atomic_xchg(&tp_var->receiving, 0) != 1)
+				break;
+
+			batadv_tp_vars_put(tp_var);
 			break;
 		}
net/batman-adv/types.h +3 -0
index d755377b573c2..7ee337d72ebb0 100644
@@ -1391,6 +1391,9 @@ struct batadv_tp_vars {
 	/** @sending: sending binary semaphore: 1 if sending, 0 is not */
 	atomic_t sending;
 
+	/** @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;
Signature · 1 line
2.47.3
maintainer
#2 lore raw

PATCH 2/2 batman-adv: tp_meter: fix race condition in send error reporting

commit 71dce47f0758537fff78fddb5fb0d4632d29b29f upstream.

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]> # 6.6.x: 5c1bf8d batman-adv: tp_meter: fix tp_vars reference leak in receiver shutdown
Cc <[email protected]> # 6.6.x
Fixes 33a3bb4a3345 ("batman-adv: throughput meter implementation")
Signed-off-by Sven Eckelmann <[email protected]>
---
 net/batman-adv/tp_meter.c | 40 ++++++++++++++++++++++++---------------
 net/batman-adv/types.h    | 10 +++++-----
 2 files changed, 30 insertions(+), 20 deletions(-)
net/batman-adv/tp_meter.c +25 -15
index 6cb1820fa4a4a..d72880dd1c643 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 = from_timer(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 7ee337d72ebb0..a115212decf4f 100644
@@ -1388,15 +1388,15 @@ 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;
Signature · 1 line
2.47.3
maintainer
#3 lore raw

Re: [PATCH 6.1.y 2/2] batman-adv: tp_meter: fix race condition in send error reporting

Quoted 2 lines · On Friday, 29 May 2026 21:49:08 CEST Sven Eckelmann wrote:
Cc <[email protected]> # 6.6.x: 5c1bf8d batman-adv: tp_meter: fix tp_vars reference leak in receiver shutdown
Cc <[email protected]> # 6.6.x

Grml, meant 6.1.x. But I've sent the required patch too.

Btw. if these dependencies between patches annd the correct order causes
headaches: I have everything in
https://git.open-mesh.org/batadv.git/log/?h=batadv/lts/6.1 (and similar branches) and can easily rebase them on top of stable-rc.git/queue/6.1 and sent the remaining patches out as a patchset for a specific stable kernel (like 6.1).

Regards,
Sven

maintainer Applied
#4 lore raw

Re: [PATCH 6.1.y 1/2] batman-adv: tp_meter: fix tp_vars reference leak in receiver shutdown

In reply to Sven Eckelmann

Queued for 5.10.y, thanks.

Signature · 2 lines
Thanks,
Sasha