* [syzbot] [can?] WARNING in __netif_receive_skb_core
@ 2026-09-15 15:56 syzbot
2026-09-17 20:31 ` Forwarded: [PATCH] can: dev: fix missing skb header initialization in init_can_skb syzbot
2026-09-17 20:39 ` syzbot
0 siblings, 2 replies; 5+ messages in thread
From: syzbot @ 2026-09-15 15:56 UTC (permalink / raw)
To: dario.binacchi, linux-can, linux-kernel, mailhol, mkl, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 704340f1cd0d Merge tag 'x86_urgent_for_7.3-rc4' of git://g..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15a62471580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f
dashboard link: https://syzkaller.appspot.com/bug?extid=1aae11dc8d42ec1a87ec
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1580bc8e580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=169f9905580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/192c594c6096/disk-704340f1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/79d1488deb4b/vmlinux-704340f1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fd108c2b8ca0/bzImage-704340f1.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1aae11dc8d42ec1a87ec@syzkaller.appspotmail.com
------------[ cut here ]------------
1
WARNING: ./include/linux/skbuff.h:3003 at skb_reset_mac_len include/linux/skbuff.h:3003 [inline], CPU#0: kworker/u8:1/13
WARNING: ./include/linux/skbuff.h:3003 at __netif_receive_skb_core.constprop.0+0x1706/0x3530 net/core/dev.c:6061, CPU#0: kworker/u8:1/13
Modules linked in:
CPU: 0 UID: 0 PID: 13 Comm: kworker/u8:1 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Workqueue: events_unbound flush_to_ldisc
RIP: 0010:skb_reset_mac_len include/linux/skbuff.h:3003 [inline]
RIP: 0010:__netif_receive_skb_core.constprop.0+0x1706/0x3530 net/core/dev.c:6061
Code: de 4c 8b bc 24 e8 00 00 00 e8 86 f7 6b f8 85 db 0f 88 11 f2 ff ff 31 db 4d 8d af 81 00 00 00 e9 01 ed ff ff e8 fb fc 6b f8 90 <0f> 0b 90 31 db e9 43 eb ff ff e8 eb fc 6b f8 e8 66 af 4f f8 31 ff
RSP: 0018:ffffc90000007990 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000040 RCX: 0000000000000101
RDX: ffff88801f2a0000 RSI: ffffffff89a02015 RDI: ffff88801f2a0000
RBP: 000000000000ffff R08: 0000000000000003 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000001 R12: ffff888075f88140
R13: ffffc90000007c10 R14: ffff888075f88140 R15: ffff888075f88140
FS: 0000000000000000(0000) GS:ffff888123b59000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd21e26870 CR3: 00000000729f5000 CR4: 00000000003526f0
Call Trace:
<IRQ>
__netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:6262
__netif_receive_skb+0x1f/0x120 net/core/dev.c:6377
process_backlog+0x487/0x1600 net/core/dev.c:6728
__napi_poll.constprop.0+0xaf/0x450 net/core/dev.c:7787
napi_poll net/core/dev.c:7850 [inline]
net_rx_action+0xa40/0xf20 net/core/dev.c:8007
handle_softirqs+0x1e6/0x9d0 kernel/softirq.c:645
do_softirq kernel/softirq.c:546 [inline]
do_softirq+0xaf/0xf0 kernel/softirq.c:533
</IRQ>
<TASK>
__local_bh_enable_ip+0xff/0x120 kernel/softirq.c:473
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx net/core/dev.c:5837 [inline]
netif_rx+0x93/0xb0 net/core/dev.c:5826
slcan_bump_err drivers/net/can/slcan/slcan-core.c:448 [inline]
slcan_bump drivers/net/can/slcan/slcan-core.c:463 [inline]
slcan_unesc drivers/net/can/slcan/slcan-core.c:476 [inline]
slcan_receive_buf+0x1a66/0x1f30 drivers/net/can/slcan/slcan-core.c:807
tty_ldisc_receive_buf+0x15a/0x1a0 drivers/tty/tty_buffer.c:398
tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
receive_buf drivers/tty/tty_buffer.c:452 [inline]
flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
process_scheduled_works kernel/workqueue.c:3479 [inline]
worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
kthread+0x373/0x450 kernel/kthread.c:436
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Forwarded: [PATCH] can: dev: fix missing skb header initialization in init_can_skb
2026-09-15 15:56 [syzbot] [can?] WARNING in __netif_receive_skb_core syzbot
@ 2026-09-17 20:31 ` syzbot
2026-09-17 20:39 ` syzbot
1 sibling, 0 replies; 5+ messages in thread
From: syzbot @ 2026-09-17 20:31 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] can: dev: fix missing skb header initialization in init_can_skb
Author: shaunakkdatar@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
__alloc_skb() sets skb->mac_header to (typeof(skb->mac_header))~0U via
__finalize_skb_around(). skb_reset_mac_len() checks if the value has been
updated via the skb_mac_header_was_set() and fires
DEBUG_NET_WARN_ON_ONCE(1) if not.
init_can_skb() previously included three header reset calls:
skb_reset_mac_header(skb)
skb_reset_network_header(skb)
skb_reset_transport_header(skb)
Commit 9f10374bb024 ("can: remove private CAN skb headroom
infrastructure") dropped these calls which leads to the skb->mac_header
retaining the original value.
Restore the three missing calls in the init_can_skb().
Fixes: 9f10374bb024 ("can: remove private CAN skb headroom infrastructure")
Reported-by: syzbot+1aae11dc8d42ec1a87ec@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1aae11dc8d42ec1a87ec
Signed-off-by: Shaunak Datar <shaunakkdatar@gmail.com>
---
drivers/net/can/dev/skb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 95fcdc1026f8..9cbddc1edd41 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -210,6 +210,9 @@ static void init_can_skb(struct sk_buff *skb)
{
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
+ skb_reset_mac_header(skb);
+ skb_reset_network_header(skb);
+ skb_reset_transport_header(skb);
}
struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
--
2.53.0
^ permalink raw reply [flat|nested] 5+ messages in thread* Forwarded: [PATCH] can: dev: fix missing skb header initialization in init_can_skb
2026-09-15 15:56 [syzbot] [can?] WARNING in __netif_receive_skb_core syzbot
2026-09-17 20:31 ` Forwarded: [PATCH] can: dev: fix missing skb header initialization in init_can_skb syzbot
@ 2026-09-17 20:39 ` syzbot
1 sibling, 0 replies; 5+ messages in thread
From: syzbot @ 2026-09-17 20:39 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] can: dev: fix missing skb header initialization in init_can_skb
Author: shaunakkdatar@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
__alloc_skb() sets skb->mac_header to (typeof(skb->mac_header))~0U via
__finalize_skb_around(). skb_reset_mac_len() checks if the value has been
updated via the skb_mac_header_was_set() and fires
DEBUG_NET_WARN_ON_ONCE(1) if not.
init_can_skb() previously included three header reset calls:
skb_reset_mac_header(skb)
skb_reset_network_header(skb)
skb_reset_transport_header(skb)
Commit 9f10374bb024 ("can: remove private CAN skb headroom
infrastructure") dropped these calls which leads to the skb->mac_header
retaining the original value.
Restore the three missing calls in the init_can_skb().
Fixes: 9f10374bb024 ("can: remove private CAN skb headroom infrastructure")
Reported-by: syzbot+1aae11dc8d42ec1a87ec@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1aae11dc8d42ec1a87ec
Signed-off-by: Shaunak Datar <shaunakkdatar@gmail.com>
---
drivers/net/can/dev/skb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 95fcdc1026f8..9cbddc1edd41 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -210,6 +210,9 @@ static void init_can_skb(struct sk_buff *skb)
{
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
+ skb_reset_mac_header(skb);
+ skb_reset_network_header(skb);
+ skb_reset_transport_header(skb);
}
struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
--
2.53.0
^ permalink raw reply [flat|nested] 5+ messages in thread
[parent not found: <20260917203124.753286-1-shaunakkdatar@gmail.com>]
[parent not found: <20260917203850.753752-1-shaunakkdatar@gmail.com>]
end of thread, other threads:[~2026-09-18 7:02 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2026-09-15 15:56 [syzbot] [can?] WARNING in __netif_receive_skb_core syzbot
2026-09-17 20:31 ` Forwarded: [PATCH] can: dev: fix missing skb header initialization in init_can_skb syzbot
2026-09-17 20:39 ` syzbot
[not found] <20260917203124.753286-1-shaunakkdatar@gmail.com>
2026-09-18 6:48 ` [syzbot] [can?] WARNING in __netif_receive_skb_core syzbot
[not found] <20260917203850.753752-1-shaunakkdatar@gmail.com>
2026-09-18 7:02 ` syzbot
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