[syzbot ci] Re: tipc: bound reassembly size in tipc_buf_append()

[syzbot ci <syzbot+ci972ab65a3669be2c@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v1] tipc: bound reassembly size in tipc_buf_append()
https://lore.kernel.org/all/AoU-V5M5ZCKF37bLl8ILhgeNdsnCEaiaQNuWP4K56kRfJsnhkIexZ8tFRLq7uzGiA0qNqK6shXcSZ5E4hyV0-QI0ZWSuKiJzKvMrv3NfqCg=@proton.me
* [PATCH] tipc: bound reassembly size in tipc_buf_append()

and found the following issue:
general protection fault in tipc_buf_append

Full report is available here:
https://ci.syzbot.org/series/3856f5b1-55ca-4bc2-885e-034eb8af1bdf

***

general protection fault in tipc_buf_append

tree:      net-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base:      c4c470912125ec8a1a427a70f4085d8a731b00e4
arch:      amd64
compiler:  Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/28264169-6c3f-405e-9f6a-339572b43e52/config
syz repro: https://ci.syzbot.org/findings/e9e2a2a5-41e6-4866-89fc-45c75bfe992b/syz_repro

Oops: general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
CPU: 1 UID: 0 PID: 5915 Comm: syz.1.18 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:tipc_buf_append+0x389/0xa20 net/tipc/msg.c:153
Code: e9 b5 01 00 00 e8 97 ea 29 f6 48 8b 44 24 20 42 80 3c 30 00 48 8b 5c 24 28 74 08 48 89 df e8 8e 74 a1 f6 48 c7 03 00 00 00 00 <41> 0f b6 46 0e 84 c0 0f 85 ea 04 00 00 8b 1c 25 70 00 00 00 4d 8d
RSP: 0018:ffffc900039defa0 EFLAGS: 00010246
RAX: 1ffff9200073be13 RBX: ffffc900039df098 RCX: ffff88810d335a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88816af130c0
RBP: ffffc900039df078 R08: ffff8881ba5f6ee3 R09: 1ffff110374beddc
R10: dffffc0000000000 R11: ffffed10374beddd R12: 1ffff1102d5e2617
R13: 1ffff9200073bdfc R14: dffffc0000000000 R15: ffff88816af12ff0
FS:  00007fbe193e76c0(0000) GS:ffff8882a7809000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbe193e6ff8 CR3: 0000000117562000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 tipc_msg_reassemble+0x230/0x3b0 net/tipc/msg.c:807
 tipc_mcast_xmit+0x254/0x19e0 net/tipc/bcast.c:392
 tipc_sendmcast net/tipc/socket.c:887 [inline]
 __tipc_sendmsg+0x2074/0x2b60 net/tipc/socket.c:1470
 tipc_sendmsg+0x55/0x70 net/tipc/socket.c:1404
 sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800
 __sock_sendmsg net/socket.c:818 [inline]
 ____sys_sendmsg+0x54e/0x850 net/socket.c:2715
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2769
 __sys_sendmmsg+0x273/0x4e0 net/socket.c:2858
 __do_sys_sendmmsg net/socket.c:2885 [inline]
 __se_sys_sendmmsg net/socket.c:2882 [inline]
 __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2882
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbe185a8f19
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:00007fbe193e7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fbe18825fa0 RCX: 00007fbe185a8f19
RDX: 0000000000000300 RSI: 0000200000006740 RDI: 0000000000000003
RBP: 00007fbe18637f6d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbe18826038 R14: 00007fbe18825fa0 R15: 00007ffeceeefb38
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:tipc_buf_append+0x389/0xa20 net/tipc/msg.c:153
Code: e9 b5 01 00 00 e8 97 ea 29 f6 48 8b 44 24 20 42 80 3c 30 00 48 8b 5c 24 28 74 08 48 89 df e8 8e 74 a1 f6 48 c7 03 00 00 00 00 <41> 0f b6 46 0e 84 c0 0f 85 ea 04 00 00 8b 1c 25 70 00 00 00 4d 8d
RSP: 0018:ffffc900039defa0 EFLAGS: 00010246
RAX: 1ffff9200073be13 RBX: ffffc900039df098 RCX: ffff88810d335a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88816af130c0
RBP: ffffc900039df078 R08: ffff8881ba5f6ee3 R09: 1ffff110374beddc
R10: dffffc0000000000 R11: ffffed10374beddd R12: 1ffff1102d5e2617
R13: 1ffff9200073bdfc R14: dffffc0000000000 R15: ffff88816af12ff0
FS:  00007fbe193e76c0(0000) GS:ffff8882a7809000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbe193e6ff8 CR3: 0000000117562000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
   0:	e9 b5 01 00 00       	jmp    0x1ba
   5:	e8 97 ea 29 f6       	call   0xf629eaa1
   a:	48 8b 44 24 20       	mov    0x20(%rsp),%rax
   f:	42 80 3c 30 00       	cmpb   $0x0,(%rax,%r14,1)
  14:	48 8b 5c 24 28       	mov    0x28(%rsp),%rbx
  19:	74 08                	je     0x23
  1b:	48 89 df             	mov    %rbx,%rdi
  1e:	e8 8e 74 a1 f6       	call   0xf6a174b1
  23:	48 c7 03 00 00 00 00 	movq   $0x0,(%rbx)
* 2a:	41 0f b6 46 0e       	movzbl 0xe(%r14),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 ea 04 00 00    	jne    0x521
  37:	8b 1c 25 70 00 00 00 	mov    0x70,%ebx
  3e:	4d                   	rex.WRB
  3f:	8d                   	.byte 0x8d


***

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: syzbot@syzkaller.appspotmail.com

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