FAILED: patch "[PATCH] net/sched: ets: use old 'nbands' while purging unused classes" failed to apply to 6.1-stable tree

PATCH New [email protected] 2 participants 3 messages Aug 18, 2025 – Aug 19, 2025

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author maintainer

2025-08-18 11:06 UTC #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 87c6efc5ce9c126ae4a781bc04504b83780e3650
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025081855-silicon-oops-12df@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 87c6efc5ce9c126ae4a781bc04504b83780e3650 Mon Sep 17 00:00:00 2001
From: Davide Caratti <[email protected]>
Date: Tue, 12 Aug 2025 18:40:29 +0200
Subject: [PATCH] net/sched: ets: use old 'nbands' while purging unused classes

Shuang reported sch_ets test-case [1] crashing in ets_class_qlen_notify() after recent changes from Lion [2]. The problem is: in ets_qdisc_change() we purge unused DWRR queues; the value of 'q->nbands' is the new one, and the cleanup should be done with the old one. The problem is here since my first attempts to fix ets_qdisc_change(), but it surfaced again after the recent qdisc len accounting fixes. Fix it purging idle DWRR queues before assigning a new value of 'q->nbands', so that all purge operations find a consistent configuration:

- old 'q->nbands' because it's needed by ets_class_find()
- old 'q->nstrict' because it's needed by ets_class_is_strict()

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: Oops: 0000 [#1] SMP NOPTI
 CPU: 62 UID: 0 PID: 39457 Comm: tc Kdump: loaded Not tainted 6.12.0-116.el10.x86_64 #1 PREEMPT(voluntary)
 Hardware name: Dell Inc. PowerEdge R640/06DKY5, BIOS 2.12.2 07/09/2021
 RIP: 0010:__list_del_entry_valid_or_report+0x4/0x80
 Code: ff 4c 39 c7 0f 84 39 19 8e ff b8 01 00 00 00 c3 cc cc cc cc 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa <48> 8b 17 48 8b 4f 08 48 85 d2 0f 84 56 19 8e ff 48 85 c9 0f 84 ab
 RSP: 0018:ffffba186009f400 EFLAGS: 00010202
 RAX: 00000000000000d6 RBX: 0000000000000000 RCX: 0000000000000004
 RDX: ffff9f0fa29b69c0 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: ffffffffc12c2400 R08: 0000000000000008 R09: 0000000000000004
 R10: ffffffffffffffff R11: 0000000000000004 R12: 0000000000000000
 R13: ffff9f0f8cfe0000 R14: 0000000000100005 R15: 0000000000000000
 FS:  00007f2154f37480(0000) GS:ffff9f269c1c0000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 00000001530be001 CR4: 00000000007726f0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 55555554
 Call Trace:
  <TASK>
  ets_class_qlen_notify+0x65/0x90 [sch_ets]
  qdisc_tree_reduce_backlog+0x74/0x110
  ets_qdisc_change+0x630/0xa40 [sch_ets]
  __tc_modify_qdisc.constprop.0+0x216/0x7f0
  tc_modify_qdisc+0x7c/0x120
  rtnetlink_rcv_msg+0x145/0x3f0
  netlink_rcv_skb+0x53/0x100
  netlink_unicast+0x245/0x390
  netlink_sendmsg+0x21b/0x470
  ____sys_sendmsg+0x39d/0x3d0
  ___sys_sendmsg+0x9a/0xe0
  __sys_sendmsg+0x7a/0xd0
  do_syscall_64+0x7d/0x160
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7f2155114084
 Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d 25 f0 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89
 RSP: 002b:00007fff1fd7a988 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
 RAX: ffffffffffffffda RBX: 0000560ec063e5e0 RCX: 00007f2155114084
 RDX: 0000000000000000 RSI: 00007fff1fd7a9f0 RDI: 0000000000000003
 RBP: 00007fff1fd7aa60 R08: 0000000000000010 R09: 000000000000003f
 R10: 0000560ee9b3a010 R11: 0000000000000202 R12: 00007fff1fd7aae0
 R13: 000000006891ccde R14: 0000560ec063e5e0 R15: 00007fff1fd7aad0
  </TASK>

[1] https://lore.kernel.org/netdev/e08c7f4a6882f260011909a868311c6e9b54f3e4.1639153474.git.dcaratti@redhat.com/
[2] https://lore.kernel.org/netdev/[email protected]/

Cc [email protected]

Fixes 103406b38c60 ("net/sched: Always pass notifications when child class becomes empty")

Fixes c062f2a0b04d ("net/sched: sch_ets: don't remove idle classes from the round-robin list")

Fixes dcc68b4d8084 ("net: sch_ets: Add a new Qdisc")

Reported-by Li Shuang <[email protected]>

Closes https://issues.redhat.com/browse/RHEL-108026

Reviewed-by Petr Machata <[email protected]>

Co-developed-by Ivan Vecera <[email protected]>

Signed-off-by Ivan Vecera <[email protected]>

Signed-off-by Davide Caratti <[email protected]>

Link https://patch.msgid.link/7928ff6d17db47a2ae7cc205c44777b1f1950545.1755016081.git.dcaratti@redhat.com open here

Signed-off-by Jakub Kicinski <[email protected]>

net/sched/sch_ets.c +6 -5

index 037f764822b9..82635dd2cfa5 100644
@@ -651,6 +651,12 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,
 
 	sch_tree_lock(sch);
 
+	for (i = nbands; i < oldbands; i++) {
+		if (i >= q->nstrict && q->classes[i].qdisc->q.qlen)
+			list_del_init(&q->classes[i].alist);
+		qdisc_purge_queue(q->classes[i].qdisc);
+	}
+
 	WRITE_ONCE(q->nbands, nbands);
 	for (i = nstrict; i < q->nstrict; i++) {
 		if (q->classes[i].qdisc->q.qlen) {

@@ -658,11 +664,6 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,
 			q->classes[i].deficit = quanta[i];
 		}
 	}
-	for (i = q->nbands; i < oldbands; i++) {
-		if (i >= q->nstrict && q->classes[i].qdisc->q.qlen)
-			list_del_init(&q->classes[i].alist);
-		qdisc_purge_queue(q->classes[i].qdisc);
-	}
 	WRITE_ONCE(q->nstrict, nstrict);
 	memcpy(q->prio2band, priomap, sizeof(priomap));

Sasha Levin

maintainer

2025-08-19 11:52 UTC #1 lore raw

PATCH 1/2 net_sched: sch_ets: implement lockless ets_dump()

From: Eric Dumazet <[email protected]>

[ Upstream commit c5f1dde7f731e7bf2e7c169ca42cb4989fc2f8b9 ]

Instead of relying on RTNL, ets_dump() can use READ_ONCE() annotations, paired with WRITE_ONCE() ones in ets_change().

Signed-off-by Eric Dumazet <[email protected]>

Reviewed-by Simon Horman <[email protected]>

Signed-off-by David S. Miller <[email protected]>

Stable-dep-of: 87c6efc5ce9c ("net/sched: ets: use old 'nbands' while purging unused classes")

Signed-off-by Sasha Levin <[email protected]>

---
 net/sched/sch_ets.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

net/sched/sch_ets.c +14 ~~-11~~

index 3ee46f6e005d..93469bc337d6 100644
@@ -651,7 +651,7 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,
 
 	sch_tree_lock(sch);
 
-	q->nbands = nbands;
+	WRITE_ONCE(q->nbands, nbands);
 	for (i = nstrict; i < q->nstrict; i++) {
 		if (q->classes[i].qdisc->q.qlen) {
 			list_add_tail(&q->classes[i].alist, &q->active);

@@ -663,11 +663,11 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,
 			list_del_init(&q->classes[i].alist);
 		qdisc_purge_queue(q->classes[i].qdisc);
 	}
-	q->nstrict = nstrict;
+	WRITE_ONCE(q->nstrict, nstrict);
 	memcpy(q->prio2band, priomap, sizeof(priomap));
 
 	for (i = 0; i < q->nbands; i++)
-		q->classes[i].quantum = quanta[i];
+		WRITE_ONCE(q->classes[i].quantum, quanta[i]);
 
 	for (i = oldbands; i < q->nbands; i++) {
 		q->classes[i].qdisc = queues[i];

@@ -681,7 +681,7 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,
 	for (i = q->nbands; i < oldbands; i++) {
 		qdisc_put(q->classes[i].qdisc);
 		q->classes[i].qdisc = NULL;
-		q->classes[i].quantum = 0;
+		WRITE_ONCE(q->classes[i].quantum, 0);
 		q->classes[i].deficit = 0;
 		gnet_stats_basic_sync_init(&q->classes[i].bstats);
 		memset(&q->classes[i].qstats, 0, sizeof(q->classes[i].qstats));

@@ -738,6 +738,7 @@ static int ets_qdisc_dump(struct Qdisc *sch, struct sk_buff *skb)
 	struct ets_sched *q = qdisc_priv(sch);
 	struct nlattr *opts;
 	struct nlattr *nest;
+	u8 nbands, nstrict;
 	int band;
 	int prio;
 	int err;

@@ -750,21 +751,22 @@ static int ets_qdisc_dump(struct Qdisc *sch, struct sk_buff *skb)
 	if (!opts)
 		goto nla_err;
 
-	if (nla_put_u8(skb, TCA_ETS_NBANDS, q->nbands))
+	nbands = READ_ONCE(q->nbands);
+	if (nla_put_u8(skb, TCA_ETS_NBANDS, nbands))
 		goto nla_err;
 
-	if (q->nstrict &&
-	    nla_put_u8(skb, TCA_ETS_NSTRICT, q->nstrict))
+	nstrict = READ_ONCE(q->nstrict);
+	if (nstrict && nla_put_u8(skb, TCA_ETS_NSTRICT, nstrict))
 		goto nla_err;
 
-	if (q->nbands > q->nstrict) {
+	if (nbands > nstrict) {
 		nest = nla_nest_start(skb, TCA_ETS_QUANTA);
 		if (!nest)
 			goto nla_err;
 
-		for (band = q->nstrict; band < q->nbands; band++) {
+		for (band = nstrict; band < nbands; band++) {
 			if (nla_put_u32(skb, TCA_ETS_QUANTA_BAND,
-					q->classes[band].quantum))
+					READ_ONCE(q->classes[band].quantum)))
 				goto nla_err;
 		}

@@ -776,7 +778,8 @@ static int ets_qdisc_dump(struct Qdisc *sch, struct sk_buff *skb)
 		goto nla_err;
 
 	for (prio = 0; prio <= TC_PRIO_MAX; prio++) {
-		if (nla_put_u8(skb, TCA_ETS_PRIOMAP_BAND, q->prio2band[prio]))
+		if (nla_put_u8(skb, TCA_ETS_PRIOMAP_BAND,
+			       READ_ONCE(q->prio2band[prio])))
 			goto nla_err;
 	}

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