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KASAN: slab-out-of-bounds Read in fib6_add_rt2node

Status: upstream: reported C repro on 2026/02/11 17:43
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+707d6a5da1ab9e0c6f9d@syzkaller.appspotmail.com
Fix commit: ipv6: Fix out-of-bound access in fib6_add_rt2node().
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 12d, last: 4h25m
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH v1 net] ipv6: Fix out-of-bound access in fib6_add_rt2node(). 4 (4) 2026/02/13 20:30
[syzbot] [net?] KASAN: slab-out-of-bounds Read in fib6_add_rt2node 0 (1) 2026/02/11 17:43
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: global-out-of-bounds Read in fib6_add_rt2node net 17 3 260d 264d 0/29 closed as invalid on 2025/07/02 15:51
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/02/09 18:36 16m kuniyu@google.com patch upstream log
2026/02/08 01:03 17m kuniyu@google.com patch upstream log

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in fib6_add_rt2node+0x349c/0x3500 net/ipv6/ip6_fib.c:1142
Read of size 1 at addr ffff8880384ba6de by task syz.0.18/5500

CPU: 0 UID: 0 PID: 5500 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 fib6_add_rt2node+0x349c/0x3500 net/ipv6/ip6_fib.c:1142
 fib6_add_rt2node_nh net/ipv6/ip6_fib.c:1363 [inline]
 fib6_add+0x910/0x18c0 net/ipv6/ip6_fib.c:1531
 __ip6_ins_rt net/ipv6/route.c:1351 [inline]
 ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3957
 inet6_rtm_newroute+0x268/0x19e0 net/ipv6/route.c:5660
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9316b9aeb9
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:00007ffd8809b678 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f9316e15fa0 RCX: 00007f9316b9aeb9
RDX: 0000000000000000 RSI: 0000200000004380 RDI: 0000000000000003
RBP: 00007f9316c08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9316e15fac R14: 00007f9316e15fa0 R15: 00007f9316e15fa0
 </TASK>

Allocated by task 5499:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5657 [inline]
 __kmalloc_noprof+0x40c/0x7e0 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 fib6_info_alloc+0x30/0xf0 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x142/0x860 net/ipv6/route.c:3820
 ip6_route_add+0x49/0x1b0 net/ipv6/route.c:3949
 inet6_rtm_newroute+0x268/0x19e0 net/ipv6/route.c:5660
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880384ba600
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 22 bytes to the right of
 allocated 200-byte region [ffff8880384ba600, ffff8880384ba6c8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x384ba
ksm flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000000 ffff88801a841b40 ffffea0000c2c780 dead000000000007
raw: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 27805093247, free_ts 22714174709
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3a0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xd82/0x1760 mm/slub.c:4656
 __slab_alloc+0x65/0x100 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kvmalloc_node_noprof+0x673/0x8d0 mm/slub.c:7144
 v4l2_ctrl_new+0x9d5/0x1790 drivers/media/v4l2-core/v4l2-ctrls-core.c:2112
 v4l2_ctrl_new_std+0x24e/0x300 drivers/media/v4l2-core/v4l2-ctrls-core.c:2266
 handler_new_ref+0x153/0x9c0 drivers/media/v4l2-core/v4l2-ctrls-core.c:1853
 v4l2_ctrl_add_handler+0x19f/0x290 drivers/media/v4l2-core/v4l2-ctrls-core.c:2416
 vivid_create_controls+0x2fdc/0x3bd0 drivers/media/test-drivers/vivid/vivid-ctrls.c:2044
 vivid_create_instance drivers/media/test-drivers/vivid/vivid-core.c:1933 [inline]
 vivid_probe+0x4261/0x72b0 drivers/media/test-drivers/vivid/vivid-core.c:2095
 platform_probe+0xf9/0x190 drivers/base/platform.c:1446
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x267/0xaf0 drivers/base/dd.c:661
page last free pid 36 tgid 36 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xbf8/0xd70 mm/page_alloc.c:2973
 vfree+0x25a/0x400 mm/vmalloc.c:3466
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3385
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340
 worker_thread+0xda6/0x1360 kernel/workqueue.c:3421
 kthread+0x726/0x8b0 kernel/kthread.c:463
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff8880384ba580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880384ba600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880384ba680: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
                                                    ^
 ffff8880384ba700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880384ba780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (35):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/07 06:13 upstream 2687c848e578 f20fc9f9 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/18 13:52 upstream 2961f841b025 39751c21 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/10 04:21 upstream 8a5203c630c6 4ab09a02 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/08 15:58 upstream e7aa57247700 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 11:55 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 11:55 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 11:55 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 11:53 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/06 17:01 upstream b7ff7151e653 97745f52 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/18 08:03 upstream 2961f841b025 39751c21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/17 12:56 upstream 970296997869 e439b951 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/17 12:40 upstream 970296997869 e439b951 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/17 08:39 upstream 970296997869 e439b951 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/17 07:34 upstream 970296997869 e439b951 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/16 19:02 upstream 0f2acd3148e0 5d52cba5 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/14 13:58 upstream 770aaedb461a 1e62d198 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/13 20:20 upstream cee73b1e840c 1e62d198 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/13 08:38 upstream 7449f86bafcd 6a673c50 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/13 00:42 upstream 37a93dd5c49b 504cb1bf .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/11 19:04 upstream 192c0159402e 75707236 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/11 15:53 upstream 192c0159402e 75707236 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/11 08:36 upstream dc855b77719f 441e25b7 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/11 07:15 upstream dc855b77719f 441e25b7 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/10 21:34 upstream 72c395024dac a076df6f .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/10 14:46 upstream 72c395024dac a076df6f .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/10 06:25 upstream 8a5203c630c6 4ab09a02 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/10 05:35 upstream 8a5203c630c6 4ab09a02 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/09 13:50 upstream 05f7e89ab973 df949cd9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/09 07:19 upstream e98f34af6116 4c131dc4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/08 17:14 upstream e7aa57247700 4c131dc4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/08 16:12 upstream e7aa57247700 4c131dc4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/08 07:17 upstream e7aa57247700 4c131dc4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 13:31 upstream 2687c848e578 f20fc9f9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 10:47 upstream 2687c848e578 f20fc9f9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
2026/02/07 04:54 upstream 2687c848e578 f20fc9f9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Read in fib6_add_rt2node
* Struck through repros no longer work on HEAD.