KASAN: slab-use-after-free Read in rtnl_fill_ifinfo

Status: upstream: reported on 2026/08/02 13:05
Reported-by: syzbot+ee0a83ffd5ebd6b71833@syzkaller.appspotmail.com
First crash: 54d, last: 39d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in rtnl_fill_ifinfo 19 3 39d 45d 0/3 upstream: reported on 2026/08/11 03:45
upstream general protection fault in rtnl_fill_ifinfo net 2 2 630d 645d 0/29 closed as invalid on 2025/02/03 10:48

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in strlen+0x57/0x70 lib/string.c:425
Read of size 1 at addr ffff888079008b40 by task kworker/u4:8/2903

CPU: 0 PID: 2903 Comm: kworker/u4:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound linkwatch_event
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 strlen+0x57/0x70 lib/string.c:425
 nla_put_string+0x19/0x30 include/net/netlink.h:1566
 rtnl_fill_ifinfo+0x1ca8/0x1e50 net/core/rtnetlink.c:1943
 rtmsg_ifinfo_build_skb+0x18b/0x260 net/core/rtnetlink.c:4084
 rtmsg_ifinfo_event net/core/rtnetlink.c:4118 [inline]
 rtmsg_ifinfo+0x8c/0x1a0 net/core/rtnetlink.c:4127
 netdev_state_change+0xfe/0x170 net/core/dev.c:1423
 linkwatch_do_dev+0x10d/0x160 net/core/link_watch.c:191
 __linkwatch_run_queue+0x417/0x670 net/core/link_watch.c:244
 linkwatch_event+0x4c/0x60 net/core/link_watch.c:287
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Allocated by task 14789:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb4/0x230 mm/slab_common.c:1027
 kvasprintf+0xec/0x1a0 lib/kasprintf.c:25
 kobject_set_name_vargs+0x61/0x110 lib/kobject.c:274
 dev_set_name+0xe3/0x140 drivers/base/core.c:3488
 usb_add_gadget+0x475/0x6f0 drivers/usb/gadget/udc/core.c:1448
 usb_add_gadget_udc_release+0x19c/0x1f0 drivers/usb/gadget/udc/core.c:1506
 dummy_udc_probe+0x68a/0x780 drivers/usb/gadget/udc/dummy_hcd.c:1120
 platform_probe+0x13b/0x1c0 drivers/base/platform.c:1376
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x247/0xae0 drivers/base/dd.c:717
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:879
 device_driver_attach+0xe0/0x1d0 drivers/base/dd.c:1206
 bind_store+0x1cc/0x210 drivers/base/bus.c:267
 kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 15725:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 kobject_cleanup lib/kobject.c:695 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x260/0x450 lib/kobject.c:737
 platform_remove+0x6d/0xe0 drivers/base/platform.c:1396
 device_remove drivers/base/dd.c:626 [inline]
 __device_release_driver drivers/base/dd.c:1351 [inline]
 device_release_driver_internal+0x408/0x6f0 drivers/base/dd.c:1374
 unbind_store+0x1a1/0x1d0 drivers/base/bus.c:244
 kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888079008b40
 which belongs to the cache kmalloc-16 of size 16
The buggy address is located 0 bytes inside of
 freed 16-byte region [ffff888079008b40, ffff888079008b50)

The buggy address belongs to the physical page:
page:ffffea0001e40200 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888079008760 pfn:0x79008
flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff888017c413c0 ffffea0001916390 ffffea0000c06490
raw: ffff888079008760 0000000000800009 00000001ffffffff 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 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 12475, tgid 12475 (syz-executor), ts 892835708153, free_ts 892755388523
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 __alloc_pages_node include/linux/gfp.h:237 [inline]
 alloc_slab_page+0x4f/0x180 mm/slub.c:1883
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node+0xa6/0x240 mm/slab_common.c:1014
 kmalloc_node include/linux/slab.h:620 [inline]
 kvmalloc_node+0x70/0x180 mm/util.c:617
 xt_jumpstack_alloc net/netfilter/x_tables.c:1377 [inline]
 xt_replace_table+0x185/0x750 net/netfilter/x_tables.c:1416
 __do_replace+0x169/0x9a0 net/ipv4/netfilter/ip_tables.c:1062
 do_replace net/ipv4/netfilter/ip_tables.c:1139 [inline]
 do_ipt_set_ctl+0xb38/0xe00 net/ipv4/netfilter/ip_tables.c:1632
 nf_setsockopt+0x263/0x280 net/netfilter/nf_sockopt.c:101
 do_sock_setsockopt+0x175/0x1a0 net/socket.c:2322
 __sys_setsockopt net/socket.c:2345 [inline]
 __do_sys_setsockopt net/socket.c:2354 [inline]
 __se_sys_setsockopt net/socket.c:2351 [inline]
 __x64_sys_setsockopt+0x182/0x200 net/socket.c:2351
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2505
 release_pages+0x208a/0x2300 mm/swap.c:1022
 tlb_batch_pages_flush mm/mmu_gather.c:99 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:294 [inline]
 tlb_flush_mmu+0x379/0x510 mm/mmu_gather.c:301
 tlb_finish_mmu+0xf4/0x220 mm/mmu_gather.c:425
 exit_mmap+0x428/0xb90 mm/mmap.c:3315
 __mmput+0x118/0x3a0 kernel/fork.c:1362
 exit_mm+0x23f/0x340 kernel/exit.c:576
 do_exit+0x909/0x2530 kernel/exit.c:877
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 get_signal+0x12a6/0x1390 kernel/signal.c:2911
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82

Memory state around the buggy address:
 ffff888079008a00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
 ffff888079008a80: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
>ffff888079008b00: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc
                                           ^
 ffff888079008b80: fa fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
 ffff888079008c00: fb fb fc fc fa fb fc fc fb fb fc fc fb fb fc fc
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/17 19:07 linux-6.6.y d27334b2888c 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in rtnl_fill_ifinfo
2026/08/17 19:05 linux-6.6.y d27334b2888c 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in rtnl_fill_ifinfo
2026/08/11 03:44 linux-6.6.y d27334b2888c 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in rtnl_fill_ifinfo
2026/08/02 13:04 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in rtnl_fill_ifinfo
* Struck through repros no longer work on HEAD.