linux-kernel - [syzbot] [can?] KMSAN: uninit-value in can

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Message-ID: <68bae75b.050a0220.192772.0190.GAE@google.com>
Date: Fri, 05 Sep 2025 06:36:27 -0700
From: syzbot <syzbot+4b8a1e4690e64b018227@...kaller.appspotmail.com>
To: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org, 
	mkl@...gutronix.de, socketcan@...tkopp.net, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [can?] KMSAN: uninit-value in can_receive (3)

Hello,

syzbot found the following issue on:

HEAD commit:    c3812b15000c Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=144ece64580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b9c31a1485dceb8e
dashboard link: https://syzkaller.appspot.com/bug?extid=4b8a1e4690e64b018227
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=177841f8580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=124ece64580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7736716fa3f9/disk-c3812b15.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/170d88657b1e/vmlinux-c3812b15.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b06f49d4c006/bzImage-c3812b15.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4b8a1e4690e64b018227@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in can_receive+0x219/0x5d0 net/can/af_can.c:654
 can_receive+0x219/0x5d0 net/can/af_can.c:654
 can_rcv+0x209/0x3a0 net/can/af_can.c:688
 __netif_receive_skb_one_core net/core/dev.c:5704 [inline]
 __netif_receive_skb+0x42b/0xa00 net/core/dev.c:5817
 process_backlog+0x4ad/0xa50 net/core/dev.c:6149
 __napi_poll+0xe7/0x980 net/core/dev.c:6902
 napi_poll net/core/dev.c:6971 [inline]
 net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093
 handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561
 __do_softirq+0x14/0x1a kernel/softirq.c:595
 do_softirq+0x9a/0x100 kernel/softirq.c:462
 __local_bh_enable_ip+0x9f/0xb0 kernel/softirq.c:389
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:919 [inline]
 __dev_queue_xmit+0x2758/0x57d0 net/core/dev.c:4493
 dev_queue_xmit include/linux/netdevice.h:3168 [inline]
 can_send+0xf1c/0x13b0 net/can/af_can.c:277
 isotp_sendmsg+0x1afc/0x2340 net/can/isotp.c:1087
 sock_sendmsg_nosec net/socket.c:711 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:726
 ____sys_sendmsg+0x903/0xb60 net/socket.c:2583
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2637
 __sys_sendmmsg+0x2ff/0x880 net/socket.c:2726
 __do_sys_sendmmsg net/socket.c:2753 [inline]
 __se_sys_sendmmsg net/socket.c:2750 [inline]
 __x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2750
 x64_sys_call+0x33c2/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4125 [inline]
 slab_alloc_node mm/slub.c:4168 [inline]
 __do_kmalloc_node mm/slub.c:4297 [inline]
 __kmalloc_node_track_caller_noprof+0x945/0x1240 mm/slub.c:4317
 kmalloc_reserve+0x23e/0x4a0 net/core/skbuff.c:609
 pskb_expand_head+0x226/0x1a60 net/core/skbuff.c:2275
 netif_skb_check_for_xdp net/core/dev.c:5081 [inline]
 netif_receive_generic_xdp net/core/dev.c:5112 [inline]
 do_xdp_generic+0x9e3/0x15a0 net/core/dev.c:5180
 __netif_receive_skb_core+0x25c3/0x6f10 net/core/dev.c:5524
 __netif_receive_skb_one_core net/core/dev.c:5702 [inline]
 __netif_receive_skb+0xca/0xa00 net/core/dev.c:5817
 process_backlog+0x4ad/0xa50 net/core/dev.c:6149
 __napi_poll+0xe7/0x980 net/core/dev.c:6902
 napi_poll net/core/dev.c:6971 [inline]
 net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093
 handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561
 __do_softirq+0x14/0x1a kernel/softirq.c:595

CPU: 1 UID: 0 PID: 5804 Comm: syz-executor907 Not tainted 6.13.0-rc7-syzkaller-00039-gc3812b15000c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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If the report is already addressed, let syzbot know by replying with:
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