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KASAN: use-after-free Read in seq_printf

Status: premoderation: reported on 2025/06/08 22:35
Reported-by: syzbot+ee2ae69099aa204983a2@syzkaller.appspotmail.com
First crash: 102d, last: 20h57m
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in seq_printf fs 19 5 130d 235d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 4h58m 4h57m 0/2 premoderation: reported on 2025/09/18 23:28
upstream KMSAN: uninit-value in seq_printf (2) fs 7 C 99 1191d 1458d 0/29 auto-closed as invalid on 2022/09/30 02:43
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 723d 828d 23/29 fixed on 2023/09/28 17:51
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf 17 1 3d18h 3d18h 0/2 premoderation: reported on 2025/09/15 09:58

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:641 [inline]
BUG: KASAN: use-after-free in string+0x21f/0x2b0 lib/vsprintf.c:723
Read of size 1 at addr ffff88810f459cb9 by task syz.4.2705/10177

CPU: 0 PID: 10177 Comm: syz.4.2705 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 string_nocheck lib/vsprintf.c:641 [inline]
 string+0x21f/0x2b0 lib/vsprintf.c:723
 vsnprintf+0xf20/0x1960 lib/vsprintf.c:2689
 seq_vprintf fs/seq_file.c:398 [inline]
 seq_printf+0x175/0x260 fs/seq_file.c:413
 input_devices_seq_show+0x1a6/0x650 drivers/input/input.c:1186
 seq_read_iter+0x93f/0xd30 fs/seq_file.c:272
 seq_read+0x3cc/0x4d0 fs/seq_file.c:162
 pde_read fs/proc/inode.c:321 [inline]
 proc_reg_read+0x1c4/0x2b0 fs/proc/inode.c:333
 vfs_read+0x1fe/0xa10 fs/read_write.c:494
 ksys_read+0x140/0x240 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f8d56a8cba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8d554d4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f8d56cd4090 RCX: 00007f8d56a8cba9
RDX: 0000000000002020 RSI: 0000200000004100 RDI: 0000000000000006
RBP: 00007f8d56b0fe19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8d56cd4128 R14: 00007f8d56cd4090 R15: 00007ffefabef358

Allocated by task 6662:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xda/0x110 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x1a7/0x330 mm/slub.c:4038
 __kmalloc_node include/linux/slab.h:418 [inline]
 kmalloc_node include/linux/slab.h:575 [inline]
 kvmalloc_node+0x88/0x130 mm/util.c:612
 kvmalloc include/linux/mm.h:833 [inline]
 kvzalloc include/linux/mm.h:841 [inline]
 netif_alloc_netdev_queues net/core/dev.c:9911 [inline]
 alloc_netdev_mqs+0x61e/0xc80 net/core/dev.c:10577
 loopback_net_init+0x39/0x150 drivers/net/loopback.c:211
 ops_init+0x1ba/0x4a0 net/core/net_namespace.c:144
 setup_net+0x36d/0xb50 net/core/net_namespace.c:345
 copy_net_ns+0x314/0x520 net/core/net_namespace.c:486
 create_new_namespaces+0x3a2/0x650 kernel/nsproxy.c:110
 copy_namespaces+0x1d1/0x220 kernel/nsproxy.c:179
 copy_process+0x11b8/0x32c0 kernel/fork.c:2271
 kernel_clone+0x23f/0x940 kernel/fork.c:2650
 __do_sys_clone kernel/fork.c:2776 [inline]
 __se_sys_clone kernel/fork.c:2760 [inline]
 __x64_sys_clone+0x176/0x1d0 kernel/fork.c:2760
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 kvfree_call_rcu+0x10c/0x620 kernel/rcu/tree.c:3539
 inet6_ifa_finish_destroy+0x129/0x1b0 net/ipv6/addrconf.c:1001
 in6_ifa_put include/net/addrconf.h:459 [inline]
 addrconf_ifdown+0x1193/0x1800 net/ipv6/addrconf.c:3924
 addrconf_notify+0x3bd/0xe90 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
 call_netdevice_notifiers_info net/core/dev.c:2054 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2066 [inline]
 call_netdevice_notifiers net/core/dev.c:2080 [inline]
 __dev_notify_flags+0x28f/0x500 net/core/dev.c:-1
 dev_change_flags+0xe8/0x1a0 net/core/dev.c:8610
 do_setlink+0xbb4/0x3ab0 net/core/rtnetlink.c:2732
 rtnl_group_changelink net/core/rtnetlink.c:3251 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3420 [inline]
 rtnl_newlink+0xd32/0x1640 net/core/rtnetlink.c:3530
 rtnetlink_rcv_msg+0x9db/0xb90 net/core/rtnetlink.c:5610
 netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2503
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5628
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x88d/0xb30 net/netlink/af_netlink.c:1914
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 ____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2376
 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2430
 __sys_sendmsg net/socket.c:2459 [inline]
 __do_sys_sendmsg net/socket.c:2468 [inline]
 __se_sys_sendmsg net/socket.c:2466 [inline]
 __x64_sys_sendmsg+0x1e2/0x2a0 net/socket.c:2466
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 insert_work+0x52/0x310 kernel/workqueue.c:1352
 __queue_work+0x923/0xca0 kernel/workqueue.c:1518
 __queue_delayed_work+0x188/0x200 kernel/workqueue.c:1672
 mod_delayed_work_on+0x7b/0xd0 kernel/workqueue.c:1746
 mod_delayed_work include/linux/workqueue.h:545 [inline]
 addrconf_mod_dad_work+0x7d/0x120 net/ipv6/addrconf.c:333
 addrconf_dad_start+0x96/0xd0 net/ipv6/addrconf.c:4104
 inet6_addr_add+0x5e5/0x950 net/ipv6/addrconf.c:3035
 inet6_rtm_newaddr+0x684/0x930 net/ipv6/addrconf.c:4961
 rtnetlink_rcv_msg+0x9db/0xb90 net/core/rtnetlink.c:5610
 netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2503
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5628
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x88d/0xb30 net/netlink/af_netlink.c:1914
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 __sys_sendto+0x41d/0x580 net/socket.c:2006
 __do_sys_sendto net/socket.c:2018 [inline]
 __se_sys_sendto net/socket.c:2014 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2014
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810f459c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 185 bytes inside of
 512-byte region [ffff88810f459c00, ffff88810f459e00)
The buggy address belongs to the page:
page:ffffea00043d1600 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88810f458000 pfn:0x10f458
head:ffffea00043d1600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea00041cf108 ffffea0004f28608 ffff888100043080
raw: ffff88810f458000 0000000000100004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 1585, ts 67020887447, free_ts 67013805359
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc+0x201/0x330 mm/slub.c:4034
 __kmalloc_node include/linux/slab.h:418 [inline]
 kmalloc_node include/linux/slab.h:575 [inline]
 kzalloc_node include/linux/slab.h:675 [inline]
 qdisc_alloc+0x79/0x740 net/sched/sch_generic.c:861
 qdisc_create_dflt+0x6b/0x3a0 net/sched/sch_generic.c:924
 attach_one_default_qdisc net/sched/sch_generic.c:1087 [inline]
 netdev_for_each_tx_queue include/linux/netdevice.h:2321 [inline]
 attach_default_qdiscs net/sched/sch_generic.c:1105 [inline]
 dev_activate+0x292/0x11c0 net/sched/sch_generic.c:1164
 __dev_open+0x3aa/0x4c0 net/core/dev.c:1551
 __dev_change_flags+0x20a/0x6a0 net/core/dev.c:8534
 dev_change_flags+0x88/0x1a0 net/core/dev.c:8605
 do_setlink+0xbb4/0x3ab0 net/core/rtnetlink.c:2732
 __rtnl_newlink net/core/rtnetlink.c:3410 [inline]
 rtnl_newlink+0x1292/0x1640 net/core/rtnetlink.c:3530
 rtnetlink_rcv_msg+0x9db/0xb90 net/core/rtnetlink.c:5610
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x7fc/0x820 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5431 [inline]
 __free_pages+0xdd/0x380 mm/page_alloc.c:5440
 __free_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab mm/slub.c:1920 [inline]
 unfreeze_partials+0x15f/0x190 mm/slub.c:2415
 put_cpu_partial+0xc1/0x180 mm/slub.c:2451
 __slab_free+0x2c9/0x3a0 mm/slub.c:3100
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x111/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x165/0x2e0 mm/slub.c:2965
 kmem_cache_alloc_node include/linux/slab.h:423 [inline]
 __alloc_skb+0x9e/0x520 net/core/skbuff.c:200
 alloc_skb include/linux/skbuff.h:1126 [inline]
 nlmsg_new include/net/netlink.h:953 [inline]
 rtmsg_ifinfo_build_skb+0x7c/0x180 net/core/rtnetlink.c:3844
 rtmsg_ifinfo_event net/core/rtnetlink.c:3880 [inline]
 rtmsg_ifinfo+0x7a/0x130 net/core/rtnetlink.c:3889

Memory state around the buggy address:
 ffff88810f459b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810f459c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810f459c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff88810f459d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810f459d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
netlink: 28 bytes leftover after parsing attributes in process `syz.4.2705'.
netlink: 96 bytes leftover after parsing attributes in process `syz.4.2705'.

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/18 07:29 android13-5.10-lts 911f602c2237 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/15 20:47 android13-5.10-lts 911f602c2237 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/12 18:33 android13-5.10-lts 43931d9f8738 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/11 13:29 android13-5.10-lts 43931d9f8738 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/11 13:28 android13-5.10-lts 43931d9f8738 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/11 13:25 android13-5.10-lts 43931d9f8738 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/11 13:12 android13-5.10-lts 43931d9f8738 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/09/11 13:07 android13-5.10-lts 43931d9f8738 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/06/20 08:51 android13-5.10-lts d76d4cd0623a ed3e87f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/06/08 22:34 android13-5.10-lts d76d4cd0623a 4826c28e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2025/06/20 11:22 android13-5.10-lts d76d4cd0623a ed3e87f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: slab-out-of-bounds Read in seq_printf
* Struck through repros no longer work on HEAD.