This is a note to let you know that I've just added the patch titled
net: sched: disallow noqueue for qdisc classes
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-sched-disallow-noqueue-for-qdisc-classes.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 96398560f26aa07e8f2969d73c8197e6a6d10407 Mon Sep 17 00:00:00 2001
From: Frederick Lawler <fred@xxxxxxxxxxxxxx>
Date: Mon, 9 Jan 2023 10:39:06 -0600
Subject: net: sched: disallow noqueue for qdisc classes
From: Frederick Lawler <fred@xxxxxxxxxxxxxx>
commit 96398560f26aa07e8f2969d73c8197e6a6d10407 upstream.
While experimenting with applying noqueue to a classful queue discipline,
we discovered a NULL pointer dereference in the __dev_queue_xmit()
path that generates a kernel OOPS:
# dev=enp0s5
# tc qdisc replace dev $dev root handle 1: htb default 1
# tc class add dev $dev parent 1: classid 1:1 htb rate 10mbit
# tc qdisc add dev $dev parent 1:1 handle 10: noqueue
# ping -I $dev -w 1 -c 1 1.1.1.1
[ 2.172856] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 2.173217] #PF: supervisor instruction fetch in kernel mode
...
[ 2.178451] Call Trace:
[ 2.178577] <TASK>
[ 2.178686] htb_enqueue+0x1c8/0x370
[ 2.178880] dev_qdisc_enqueue+0x15/0x90
[ 2.179093] __dev_queue_xmit+0x798/0xd00
[ 2.179305] ? _raw_write_lock_bh+0xe/0x30
[ 2.179522] ? __local_bh_enable_ip+0x32/0x70
[ 2.179759] ? ___neigh_create+0x610/0x840
[ 2.179968] ? eth_header+0x21/0xc0
[ 2.180144] ip_finish_output2+0x15e/0x4f0
[ 2.180348] ? dst_output+0x30/0x30
[ 2.180525] ip_push_pending_frames+0x9d/0xb0
[ 2.180739] raw_sendmsg+0x601/0xcb0
[ 2.180916] ? _raw_spin_trylock+0xe/0x50
[ 2.181112] ? _raw_spin_unlock_irqrestore+0x16/0x30
[ 2.181354] ? get_page_from_freelist+0xcd6/0xdf0
[ 2.181594] ? sock_sendmsg+0x56/0x60
[ 2.181781] sock_sendmsg+0x56/0x60
[ 2.181958] __sys_sendto+0xf7/0x160
[ 2.182139] ? handle_mm_fault+0x6e/0x1d0
[ 2.182366] ? do_user_addr_fault+0x1e1/0x660
[ 2.182627] __x64_sys_sendto+0x1b/0x30
[ 2.182881] do_syscall_64+0x38/0x90
[ 2.183085] entry_SYSCALL_64_after_hwframe+0x63/0xcd
...
[ 2.187402] </TASK>
Previously in commit d66d6c3152e8 ("net: sched: register noqueue
qdisc"), NULL was set for the noqueue discipline on noqueue init
so that __dev_queue_xmit() falls through for the noqueue case. This
also sets a bypass of the enqueue NULL check in the
register_qdisc() function for the struct noqueue_disc_ops.
Classful queue disciplines make it past the NULL check in
__dev_queue_xmit() because the discipline is set to htb (in this case),
and then in the call to __dev_xmit_skb(), it calls into htb_enqueue()
which grabs a leaf node for a class and then calls qdisc_enqueue() by
passing in a queue discipline which assumes ->enqueue() is not set to NULL.
Fix this by not allowing classes to be assigned to the noqueue
discipline. Linux TC Notes states that classes cannot be set to
the noqueue discipline. [1] Let's enforce that here.
Links:
1. https://linux-tc-notes.sourceforge.net/tc/doc/sch_noqueue.txt
Fixes: d66d6c3152e8 ("net: sched: register noqueue qdisc")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Frederick Lawler <fred@xxxxxxxxxxxxxx>
Reviewed-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230109163906.706000-1-fred@xxxxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sched/sch_api.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1114,6 +1114,11 @@ skip:
return -ENOENT;
}
+ if (new && new->ops == &noqueue_qdisc_ops) {
+ NL_SET_ERR_MSG(extack, "Cannot assign noqueue to a class");
+ return -EINVAL;
+ }
+
err = cops->graft(parent, cl, new, &old, extack);
if (err)
return err;
Patches currently in stable-queue which might be from fred@xxxxxxxxxxxxxx are
queue-5.10/net-sched-disallow-noqueue-for-qdisc-classes.patch
