[syzbot ci] Re: misc chandef cleanups

[syzbot ci]

syzbot ci has tested the following series

[v3] misc chandef cleanups
https://lore.kernel.org/all/20260312045804.3629...@morsemicro.com
* [PATCH wireless-next v3 1/3] wifi: mac80211: don't use cfg80211_chandef_create() for default chandef
* [PATCH wireless-next v3 2/3] wifi: cfg80211: restrict cfg80211_chandef_create() to only HT-based bands
* [PATCH wireless-next v3 3/3] wifi: cfg80211: check non-S1G width with S1G chandef

and found the following issue:
WARNING in cfg80211_chandef_create

Full report is available here:
https://ci.syzbot.org/series/ce6fc7d6-d8d4-4d00-a746-db78cba13e47

***

WARNING in cfg80211_chandef_create

tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 80234b5ab240f52fa45d201e899e207b9265ef91
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/0a18d006-45de-4bb2-a6e2-2cbb788bd2f5/config
C repro: https://ci.syzbot.org/findings/c279480a-56a9-4a59-b533-0033d65eca62/c_repro
syz repro: https://ci.syzbot.org/findings/c279480a-56a9-4a59-b533-0033d65eca62/syz_repro

netlink: 8 bytes leftover after parsing attributes in process `syz.0.17'.
------------[ cut here ]------------
chan->band == NL80211_BAND_60GHZ || chan->band == NL80211_BAND_S1GHZ
WARNING: net/wireless/chan.c:35 at cfg80211_chandef_create+0x99/0x3d0 net/wireless/chan.c:34, CPU#1: syz.0.17/5951
Modules linked in:
CPU: 1 UID: 0 PID: 5951 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:cfg80211_chandef_create+0x99/0x3d0 net/wireless/chan.c:34
Code: 8b 26 4c 89 e7 48 c7 c6 40 d6 e3 8f e8 a0 7d bd f6 49 83 fc 04 74 0d 41 83 fc 02 75 12 e8 0f 78 bd f6 eb 05 e8 08 78 bd f6 90 <0f> 0b 90 eb 05 e8 fd 77 bd f6 89 ef 48 c7 c6 60 d6 e3 8f e8 6f 7d
RSP: 0018:ffffc900054fef78 EFLAGS: 00010293
RAX: ffffffff8b0825a8 RBX: ffffc900054ff0e0 RCX: ffff888112b5ba80
RDX: 0000000000000000 RSI: ffffffff8fe3d640 RDI: 0000000000000004
RBP: 0000000000000002 R08: ffff888112b5ba80 R09: 0000000000000002
R10: 0000000000000004 R11: 0000000000000000 R12: 0000000000000004
R13: dffffc0000000000 R14: ffff888111c65998 R15: ffffc900054ff0e8
FS: 000055558dcaa500(0000) GS:ffff8882a9463000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f14d1588095 CR3: 000000010668a000 CR4: 00000000000006f0
Call Trace:
<TASK>
_nl80211_parse_chandef+0x438/0x1160 net/wireless/nl80211.c:3616
__nl80211_set_channel+0x1fe/0x850 net/wireless/nl80211.c:3736
nl80211_set_wiphy+0x116b/0x2fa0 net/wireless/nl80211.c:-1
genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0ea239c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe7ad20a38 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f0ea2615fa0 RCX: 00007f0ea239c799
RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000003
RBP: 00007f0ea2432bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0ea2615fac R14: 00007f0ea2615fa0 R15: 00007f0ea2615fa0
</TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syz...@syzkaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzk...@googlegroups.com.

[Johannes Berg]

On Fri, 2026-03-13 at 01:45 -0700, syzbot ci wrote:
> syzbot ci has tested the following series
>
> [v3] misc chandef cleanups
> https://lore.kernel.org/all/20260312045804.3629...@morsemicro.com
> * [PATCH wireless-next v3 1/3] wifi: mac80211: don't use cfg80211_chandef_create() for default chandef
> * [PATCH wireless-next v3 2/3] wifi: cfg80211: restrict cfg80211_chandef_create() to only HT-based bands
> * [PATCH wireless-next v3 3/3] wifi: cfg80211: check non-S1G width with S1G chandef
>
> and found the following issue:
> WARNING in cfg80211_chandef_create
>
> Full report is available here:
> https://ci.syzbot.org/series/ce6fc7d6-d8d4-4d00-a746-db78cba13e47
>
> ***
>
> WARNING in cfg80211_chandef_create

D'oh, just after I apply it.

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 3e867930e253..7314312ec567 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -3634,8 +3634,6 @@ static int _nl80211_parse_chandef(struct cfg80211_registered_device *rdev,
case NL80211_CHAN_HT20:
case NL80211_CHAN_HT40PLUS:
case NL80211_CHAN_HT40MINUS:
- cfg80211_chandef_create(chandef, chandef->chan,
- chantype);
/* user input for center_freq is incorrect */
if (attrs[NL80211_ATTR_CENTER_FREQ1] &&
chandef->center_freq1 != nla_get_u32(attrs[NL80211_ATTR_CENTER_FREQ1])) {
@@ -3652,6 +3650,11 @@ static int _nl80211_parse_chandef(struct cfg80211_registered_device *rdev,
"center frequency 2 can't be used");
return -EINVAL;
}
+ if (chandef->chan->band == NL80211_BAND_60GHZ ||
+ chandef->chan->band == NL80211_BAND_S1GHZ)
+ return -EINVAL;
+ cfg80211_chandef_create(chandef, chandef->chan,
+ chantype);
break;
default:
NL_SET_ERR_MSG_ATTR(extack,


I think?

johannes

[Lachlan Hodges]

On Fri, Mar 13, 2026 at 10:05:15AM +0100, Johannes Berg wrote:
> On Fri, 2026-03-13 at 01:45 -0700, syzbot ci wrote:
> > syzbot ci has tested the following series
> >
> > [v3] misc chandef cleanups
> > https://lore.kernel.org/all/20260312045804.3629...@morsemicro.com
> > * [PATCH wireless-next v3 1/3] wifi: mac80211: don't use cfg80211_chandef_create() for default chandef
> > * [PATCH wireless-next v3 2/3] wifi: cfg80211: restrict cfg80211_chandef_create() to only HT-based bands
> > * [PATCH wireless-next v3 3/3] wifi: cfg80211: check non-S1G width with S1G chandef
> >
> > and found the following issue:
> > WARNING in cfg80211_chandef_create
> >
> > Full report is available here:
> > https://ci.syzbot.org/series/ce6fc7d6-d8d4-4d00-a746-db78cba13e47
> >
> > ***
> >
> > WARNING in cfg80211_chandef_create
>
> D'oh, just after I apply it.

That didn't take long ^.^

I'm probably misunderstanding - but cfg80211_chandef_create() modifies
chandef->center_freq1 if you have a HT40+/- chantype wouldn't you
wanna do that before you validate against the CENTER_FREQ1 attribute?
Since in the generic init code above it sets cf1 to the control freq?

[...]
chandef->center_freq1 = KHZ_TO_MHZ(control_freq);
[...]

where it wouldn't match for HT40-/+ since im guessing the CF1 sent
down should be what it would be _after_ being set by
cfg80211_create_chandef() based on the chantype? Or am i missing
something?

lachlan

[Johannes Berg]

Oh, yeah, oops.

> Since in the generic init code above it sets cf1 to the control freq?
>
> [...]
> chandef->center_freq1 = KHZ_TO_MHZ(control_freq);
> [...]
>
> where it wouldn't match for HT40-/+ since im guessing the CF1 sent
> down should be what it would be _after_ being set by
> cfg80211_create_chandef() based on the chantype? Or am i missing
> something?

No, I just didn't think about it. I moved it because I thought I'd do
this differently, but this validation can just come first anyway.

johannes