linux-kernel - Re: [syzbot] [ocfs2?] kernel BUG in ocfs2_set_new_buffer

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Message-ID: <6901d6a4.050a0220.3344a1.041a.GAE@google.com>
Date: Wed, 29 Oct 2025 01:56:04 -0700
From: syzbot <syzbot+7aef76bdb53b83d62a9e@...kaller.appspotmail.com>
To: dmantipov@...dex.ru, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ocfs2?] kernel BUG in ocfs2_set_new_buffer_uptodate (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
UBSAN: signed-integer-overflow in ip_idents_reserve

================================================================================
UBSAN: signed-integer-overflow in ./arch/x86/include/asm/atomic.h:165:11
-936049278 + -1759288793 cannot be represented in type 'int'
CPU: 0 PID: 6874 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <IRQ>
 dump_stack+0xfd/0x16e lib/dump_stack.c:118
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:148
 handle_overflow+0x192/0x1b0 lib/ubsan.c:180
 arch_atomic_add_return arch/x86/include/asm/atomic.h:165 [inline]
 atomic_add_return include/asm-generic/atomic-instrumented.h:73 [inline]
 ip_idents_reserve+0x14a/0x170 net/ipv4/route.c:521
 __ip_select_ident+0xe4/0x1c0 net/ipv4/route.c:538
 iptunnel_xmit+0x466/0x7b0 net/ipv4/ip_tunnel_core.c:80
 udp_tunnel_xmit_skb+0x1ba/0x290 net/ipv4/udp_tunnel_core.c:190
 geneve_xmit_skb drivers/net/geneve.c:1004 [inline]
 geneve_xmit+0x1d05/0x2140 drivers/net/geneve.c:1117
 __netdev_start_xmit include/linux/netdevice.h:4824 [inline]
 netdev_start_xmit include/linux/netdevice.h:4838 [inline]
 xmit_one net/core/dev.c:3601 [inline]
 dev_hard_start_xmit+0x294/0x780 net/core/dev.c:3617
 __dev_queue_xmit+0x1678/0x28b0 net/core/dev.c:4203
 neigh_output include/net/neighbour.h:509 [inline]
 ip6_finish_output2+0x1020/0x1490 net/ipv6/ip6_output.c:130
 NF_HOOK+0x45/0x2c0 include/linux/netfilter.h:297
 mld_sendpack+0x5f9/0xa70 net/ipv6/mcast.c:1676
 mld_send_cr net/ipv6/mcast.c:1972 [inline]
 mld_ifc_timer_expire+0x7e1/0x990 net/ipv6/mcast.c:2471
 call_timer_fn+0x105/0x440 kernel/time/timer.c:1444
 expire_timers kernel/time/timer.c:1489 [inline]
 __run_timers+0x5d8/0x7a0 kernel/time/timer.c:1783
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1796
 __do_softirq+0x23c/0x8ae kernel/softirq.c:298
 asm_call_irq_on_stack+0xf/0x20
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
 do_softirq_own_stack+0x6d/0xb0 arch/x86/kernel/irq_64.c:77
 do_softirq+0xa9/0xf0 kernel/softirq.c:343
 __local_bh_enable_ip+0x10e/0x170 kernel/softirq.c:195
 rcu_read_unlock_bh include/linux/rcupdate.h:806 [inline]
 __dev_queue_xmit+0x1824/0x28b0 net/core/dev.c:4230
 __netlink_deliver_tap_skb net/netlink/af_netlink.c:297 [inline]
 __netlink_deliver_tap+0x50e/0x740 net/netlink/af_netlink.c:315
 netlink_deliver_tap+0x175/0x180 net/netlink/af_netlink.c:328
 __netlink_sendskb net/netlink/af_netlink.c:1257 [inline]
 netlink_sendskb+0x64/0x140 net/netlink/af_netlink.c:1266
 netlink_ack+0x8c0/0xc00 net/netlink/af_netlink.c:2473
 netlink_rcv_skb+0x1fc/0x390 net/netlink/af_netlink.c:2509
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x7b7/0x9b0 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x968/0xb50 net/netlink/af_netlink.c:1914
 sock_sendmsg_nosec net/socket.c:651 [inline]
 __sock_sendmsg+0x15c/0x170 net/socket.c:663
 __sys_sendto+0x323/0x430 net/socket.c:2005
 __do_sys_sendto net/socket.c:2017 [inline]
 __se_sys_sendto net/socket.c:2013 [inline]
 __x64_sys_sendto+0xda/0xf0 net/socket.c:2013
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x67/0xd1
RIP: 0033:0x7f2fd8c899e3
Code: 64 89 02 48 c7 c0 ff ff ff ff eb b7 66 2e 0f 1f 84 00 00 00 00 00 90 80 3d 81 7b 21 00 00 41 89 ca 74 14 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 75 c3 0f 1f 40 00 55 48 83 ec 30 44 89 4c 24
RSP: 002b:00007fff58713e38 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f2fd99fd620 RCX: 00007f2fd8c899e3
RDX: 0000000000000020 RSI: 00007f2fd99fd670 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007fff58713e54 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f2fd99fd670 R15: 0000000000000000
================================================================================


Tested on:

commit:         d3d0b4e2 Linux 5.10.245
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git linux-5.10.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12be9932580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=39182a54870857eb
dashboard link: https://syzkaller.appspot.com/bug?extid=7aef76bdb53b83d62a9e
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16911258580000