Subject: [syzbot] [net?] general protection fault in ife_tlv_meta_encode

From: syzbot <[email-masked]>
Date: Wed, 21 Jan 2026 05:35:25 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    c03e9c42ae8f Merge tag 'dma-mapping-6.19-2026-01-20' of gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12ce73fa580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf914f193dffde3bd3c
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c03e9c42.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b6abca6c0155/vmlinux-c03e9c42.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1bcd936b6484/bzImage-c03e9c42.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 3 UID: 0 PID: 8990 Comm: syz.0.696 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:ife_tlv_meta_encode+0x41/0xa0 net/ife/ife.c:166
Code: 89 d5 53 89 f3 c1 e3 10 e8 8c ed 71 f6 0f b7 c5 4c 89 ea 44 8d 78 07 83 c0 04 48 c1 ea 03 09 c3 48 b8 00 00 00 00 00 fc ff df <0f> b6 14 02 4c 89 e8 0f cb 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75
RSP: 0018:ffffc900038cf238 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000010008 RCX: ffffc900038cf290
RDX: 0000000000000000 RSI: ffffffff8b4c7434 RDI: 0000000000000000
RBP: 0000000000000004 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000001000 R11: 000000000000001e R12: ffffc900038cf290
R13: 0000000000000000 R14: 0000000000000004 R15: 000000000000000b
FS:  0000000000000000(0000) GS:ffff8880979f6000(0063) knlGS:00000000f544db40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f544cfac CR3: 000000006a9f4000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 ife_encode_meta_u32+0x153/0x180 net/sched/act_ife.c:101
 tcf_ife_encode net/sched/act_ife.c:841 [inline]
 tcf_ife_act+0x1022/0x1de0 net/sched/act_ife.c:877
 tc_act include/net/tc_wrapper.h:130 [inline]
 tcf_action_exec+0x1c0/0xa20 net/sched/act_api.c:1152
 tcf_exts_exec include/net/pkt_cls.h:349 [inline]
 mall_classify+0x1a0/0x2a0 net/sched/cls_matchall.c:42
 tc_classify include/net/tc_wrapper.h:197 [inline]
 __tcf_classify net/sched/cls_api.c:1764 [inline]
 tcf_classify+0x7f2/0x1380 net/sched/cls_api.c:1860
 multiq_classify net/sched/sch_multiq.c:39 [inline]
 multiq_enqueue+0xe0/0x510 net/sched/sch_multiq.c:66
 dev_qdisc_enqueue+0x45/0x250 net/core/dev.c:4147
 __dev_xmit_skb net/core/dev.c:4262 [inline]
 __dev_queue_xmit+0x2998/0x46c0 net/core/dev.c:4798
 dev_queue_xmit include/linux/netdevice.h:3381 [inline]
 packet_xmit+0x23e/0x350 net/packet/af_packet.c:275
 packet_snd net/packet/af_packet.c:3076 [inline]
 packet_sendmsg+0x26e3/0x54a0 net/packet/af_packet.c:3108
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa5d/0xc30 net/socket.c:2592
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2646
 __sys_sendmsg+0x16d/0x220 net/socket.c:2678
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe8/0x680 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf705d579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f544d55c EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00000000800000c0
RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ife_tlv_meta_encode+0x41/0xa0 net/ife/ife.c:166
Code: 89 d5 53 89 f3 c1 e3 10 e8 8c ed 71 f6 0f b7 c5 4c 89 ea 44 8d 78 07 83 c0 04 48 c1 ea 03 09 c3 48 b8 00 00 00 00 00 fc ff df <0f> b6 14 02 4c 89 e8 0f cb 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75
RSP: 0018:ffffc900038cf238 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000010008 RCX: ffffc900038cf290
RDX: 0000000000000000 RSI: ffffffff8b4c7434 RDI: 0000000000000000
RBP: 0000000000000004 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000001000 R11: 000000000000001e R12: ffffc900038cf290
R13: 0000000000000000 R14: 0000000000000004 R15: 000000000000000b
FS:  0000000000000000(0000) GS:ffff8880979f6000(0063) knlGS:00000000f544db40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f544cfac CR3: 000000006a9f4000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	89 d5                	mov    %edx,%ebp
   2:	53                   	push   %rbx
   3:	89 f3                	mov    %esi,%ebx
   5:	c1 e3 10             	shl    $0x10,%ebx
   8:	e8 8c ed 71 f6       	call   0xf671ed99
   d:	0f b7 c5             	movzwl %bp,%eax
  10:	4c 89 ea             	mov    %r13,%rdx
  13:	44 8d 78 07          	lea    0x7(%rax),%r15d
  17:	83 c0 04             	add    $0x4,%eax
  1a:	48 c1 ea 03          	shr    $0x3,%rdx
  1e:	09 c3                	or     %eax,%ebx
  20:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  27:	fc ff df
* 2a:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2e:	4c 89 e8             	mov    %r13,%rax
  31:	0f cb                	bswap  %ebx
  33:	83 e0 07             	and    $0x7,%eax
  36:	83 c0 03             	add    $0x3,%eax
  39:	38 d0                	cmp    %dl,%al
  3b:	7c 04                	jl     0x41
  3d:	84 d2                	test   %dl,%dl
  3f:	75                   	.byte 0x75

---
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