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KASAN: use-after-free Read in qdisc_pkt_len_segs_init

Status: upstream: reported on 2026/04/14 11:58
Subsystems: bridge
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+83181a31faf9455499c5@syzkaller.appspotmail.com
First crash: 55d, last: 8h47m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
b9289223-bc19-435d-811a-1918fdda196b assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ KASAN: use-after-free Read in qdisc_pkt_len_segs_init 2026/05/30 12:58 2026/05/30 12:58 2026/05/30 14:27 6b4a844333e83556da95d61d7f207e7ef5cd4bc6
50cbb0ef-9a10-445c-9fa3-0feddbddceb6 assessment-security 💥 KASAN: use-after-free Read in qdisc_pkt_len_segs_init 2026/05/14 10:14 2026/05/14 10:14 2026/05/14 10:15 6ccb967e465e832a7bfd7a116ad00d52a0923a5d failed to run ["git" "pull" "origin" "HEAD" "--depth=1" "--allow-unrelated-histories"]: exit status 128 From /app/workdir/repo/linux * branch HEAD -> FETCH_HEAD Updating files: 28% (26313/93691) Updating files: 29% (27171/93691) Updating files: 30% (28108/93691) Updating files: 31% (29045/93691) Updating files: 32% (29982/93691) Updating files: 33% (30919/93691) Updating files: 34% (31855/93691) Updating files: 35% (32792/93691) Updating files: 36% (33729/93691) Updating files: 36% (34201/93691) Updating files: 37% (34666/93691) Updating files: 38% (35603/93691) Updating files: 39% (36540/93691) Updating files: 39% (37255/93691) Updating files: 39% (37353/93691) error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_3_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_3_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_11_5_0_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_11_5_0_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_12_0_0_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_12_0_0_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_12_1_0_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_12_1_0_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_default.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_1_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_1_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_2_1_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_2_1_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_4_1_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_4_1_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_4_2_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_4_2_sh_mask.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_4_3_offset.h error: unable to write file drivers/gpu/drm/amd/include/asic_reg/gc/gc_9_4_3_sh_mask.h fatal: cannot create directory at 'drivers/gpu/drm/amd/include/asic_reg/gca': No space left on device
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[syzbot] Monthly bridge report (May 2026) 0 (1) 2026/05/08 20:32
[PATCH net v2] net: iptunnel: fix stale transport header after GRE/TEB decap 5 (5) 2026/04/24 02:04
[PATCH net v1 1/2] net: tunnel: fix stale transport header after GRE/TEB decap 1 (1) 2026/04/16 03:46
[syzbot] [bridge?] KASAN: use-after-free Read in qdisc_pkt_len_segs_init 0 (1) 2026/04/14 11:58

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __tcp_hdrlen include/linux/tcp.h:31 [inline]
BUG: KASAN: use-after-free in qdisc_pkt_len_segs_init+0x7f8/0xa30 net/core/dev.c:4140
Read of size 2 at addr ffff888153c3edf4 by task syz.6.1983/13471

CPU: 0 UID: 0 PID: 13471 Comm: syz.6.1983 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 __tcp_hdrlen include/linux/tcp.h:31 [inline]
 qdisc_pkt_len_segs_init+0x7f8/0xa30 net/core/dev.c:4140
 sch_handle_ingress net/core/dev.c:4477 [inline]
 __netif_receive_skb_core+0x13bd/0x3170 net/core/dev.c:6053
 __netif_receive_skb_list_core+0x24d/0x810 net/core/dev.c:6277
 __netif_receive_skb_list net/core/dev.c:6344 [inline]
 netif_receive_skb_list_internal+0x995/0xcf0 net/core/dev.c:6435
 gro_normal_list include/net/gro.h:523 [inline]
 gro_flush_normal include/net/gro.h:531 [inline]
 napi_complete_done+0x299/0x730 net/core/dev.c:6803
 gro_cell_poll+0x5a9/0x5d0 net/core/gro_cells.c:74
 __napi_poll+0xae/0x340 net/core/dev.c:7733
 napi_poll net/core/dev.c:7796 [inline]
 net_rx_action+0x627/0xf70 net/core/dev.c:7953
 handle_softirqs+0x22a/0x840 kernel/softirq.c:622
 do_softirq+0x76/0xd0 kernel/softirq.c:523
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 tun_rx_batched+0x617/0x790 drivers/net/tun.c:-1
 tun_get_user+0x2bbc/0x43e0 drivers/net/tun.c:1955
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:2001
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61d/0xb90 fs/read_write.c:688
 ksys_write+0x150/0x270 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc1a1b9ce59
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:00007fc1a2a1e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc1a1e15fa0 RCX: 00007fc1a1b9ce59
RDX: 000000000000fdef RSI: 0000200000000440 RDI: 0000000000000003
RBP: 00007fc1a1c32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc1a1e16038 R14: 00007fc1a1e15fa0 R15: 00007ffe1a965cc8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x153c3e
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 ffffea00054f0f88 ffffea00054f0f88 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff888153c3ec80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888153c3ed00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888153c3ed80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff888153c3ee00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888153c3ee80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (46):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/02 03:50 upstream e43ffb69e043 1095583b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/07 18:18 upstream 19cbc75c56c0 e358bca5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/07 06:54 upstream 5862221fdded f250db59 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/06 20:46 upstream adc1e5c6203c cbcd9ea0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/26 21:18 upstream 897d54018cc9 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/21 16:42 upstream b4e07588e743 0b6ab7ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/24 05:44 upstream 4cbfe4502e3d c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/21 17:22 upstream 8bc67e4db64a e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/21 16:21 upstream 8bc67e4db64a e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/16 12:06 upstream 6916d5703ddf a15a64a6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/23 08:15 upstream 2a4c0c11c019 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/19 07:16 upstream eb5249b12507 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/30 01:15 upstream 9215e74f228f 6b4a8443 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/23 05:03 upstream cca95436be15 c69befb3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/15 05:12 upstream 66182ca873a4 6ccb967e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/06 00:42 upstream 9207d47f966b 26da2c66 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/05 09:13 upstream a293ec25d59d 114c483e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/04 21:45 upstream c7e4e4d5f7dc a898ba9c .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/04 09:56 upstream 6d35786de281 85f1bcf2 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/01 12:21 upstream 26fd6bff2c05 753c55b9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/24 14:08 upstream dd6c438c3e64 629ff21a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/24 13:29 upstream dd6c438c3e64 629ff21a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/17 02:41 upstream 3cd8b194bf34 de0a551d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/22 13:25 net 68993ced0f61 e16cf9f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/08 11:17 net fcee7d82f27d 5633175a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/08 02:15 net 41ae14071cd7 e358bca5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/07 22:15 net 41ae14071cd7 e358bca5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/06/04 06:41 net-next a87533a80831 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/06/03 03:43 net-next cfa5274a5dc2 3c0d2131 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/06/02 22:10 net-next 51e4eca2d360 62fe1528 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/29 20:02 net-next 841559836550 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/23 06:30 net-next bde2a04d9b6f c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/12 00:56 net-next 63751099502d d168f260 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/05 00:32 net-next 98878ed91b68 a898ba9c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/01 14:33 net-next edf4bee4215a 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/26 21:59 net-next e728258debd5 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/24 10:28 net-next e728258debd5 9cfb3ca7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/18 13:32 net-next 1f5ffc672165 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/13 00:48 net-next 17ad4759a082 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/12 20:25 net-next 17ad4759a082 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/04/10 01:30 net-next 9700282a7ec7 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: use-after-free Read in qdisc_pkt_len_segs_init
2026/05/26 01:27 upstream e8c2f9fdadee c69befb3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 BUG: unable to handle kernel paging request in qdisc_pkt_len_segs_init
2026/05/26 01:27 upstream e8c2f9fdadee c69befb3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 BUG: unable to handle kernel paging request in qdisc_pkt_len_segs_init
2026/04/25 07:10 upstream 27d128c1cff6 9c2d0995 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 BUG: unable to handle kernel paging request in qdisc_pkt_len_segs_init
2026/04/24 00:33 upstream 2e6803928193 629ff21a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 BUG: unable to handle kernel paging request in qdisc_pkt_len_segs_init
* Struck through repros no longer work on HEAD.