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ca18e2360f4ac-93e8817de47mr899103039f.8.1760852164085; Sat, 18 Oct 2025 22:36:04 -0700 (PDT) Date: Sat, 18 Oct 2025 22:36:04 -0700 In-Reply-To: X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68f478c4.050a0220.91a22.0435.GAE@google.com> Subject: Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in nr_add_node From: syzbot To: linux-kernel@vger.kernel.org, listout@listout.xyz, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: KASAN: slab-use-after-free Read in nr_add_node ================================================================== BUG: KASAN: slab-use-after-free in nr_add_node+0x25e5/0x2c10 net/netrom/nr_route.c:249 Read of size 4 at addr ffff88802b876030 by task syz.2.1937/10375 CPU: 0 UID: 0 PID: 10375 Comm: syz.2.1937 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 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xcd/0x630 mm/kasan/report.c:482 kasan_report+0xe0/0x110 mm/kasan/report.c:595 nr_add_node+0x25e5/0x2c10 net/netrom/nr_route.c:249 nr_rt_ioctl+0x11b7/0x29b0 net/netrom/nr_route.c:653 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x118/0x280 net/socket.c:1254 sock_ioctl+0x227/0x6b0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f35ebf8efc9 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:00007f35ecd77038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f35ec1e5fa0 RCX: 00007f35ebf8efc9 RDX: 0000200000000280 RSI: 000000000000890b RDI: 0000000000000004 RBP: 00007f35ec011f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f35ec1e6038 R14: 00007f35ec1e5fa0 R15: 00007ffff17dcae8 Allocated by task 10366: kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 kasan_save_track+0x14/0x30 mm/kasan/common.c:77 poison_kmalloc_redzone mm/kasan/common.c:400 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417 kmalloc_noprof include/linux/slab.h:957 [inline] nr_add_node+0xe4e/0x2c10 net/netrom/nr_route.c:146 nr_rt_ioctl+0x11b7/0x29b0 net/netrom/nr_route.c:653 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x118/0x280 net/socket.c:1254 sock_ioctl+0x227/0x6b0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88802b876000 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 48 bytes inside of freed 64-byte region [ffff88802b876000, ffff88802b876040) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2b876 flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000000 ffff88801b4428c0 ffffea0000926300 dead000000000006 raw: 0000000000000000 0000000000200020 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 6284, tgid 6284 (syz-executor), ts 96678923529, free_ts 96199339256 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1850 prep_new_page mm/page_alloc.c:1858 [inline] get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3884 __alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5183 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416 alloc_slab_page mm/slub.c:3046 [inline] allocate_slab mm/slub.c:3219 [inline] new_slab+0x24a/0x360 mm/slub.c:3273 ___slab_alloc+0xdc4/0x1ae0 mm/slub.c:4643 __slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4762 __slab_alloc_node mm/slub.c:4838 [inline] slab_alloc_node mm/slub.c:5260 [inline] __kmalloc_cache_noprof+0x477/0x780 mm/slub.c:5750 kmalloc_noprof include/linux/slab.h:957 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] mpls_add_dev net/mpls/af_mpls.c:1443 [inline] mpls_dev_notify+0x346/0xa20 net/mpls/af_mpls.c:1600 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2229 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline] call_netdevice_notifiers net/core/dev.c:2281 [inline] register_netdevice+0x182e/0x2270 net/core/dev.c:11332 nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1059 [inline] nsim_create+0xdd5/0x1260 drivers/net/netdevsim/netdev.c:1141 __nsim_dev_port_add+0x435/0x7d0 drivers/net/netdevsim/dev.c:1438 nsim_dev_port_add_all drivers/net/netdevsim/dev.c:1494 [inline] nsim_drv_probe+0xe40/0x1520 drivers/net/netdevsim/dev.c:1653 call_driver_probe drivers/base/dd.c:581 [inline] really_probe+0x241/0xa90 drivers/base/dd.c:659 page last free pid 6298 tgid 6298 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1394 [inline] __free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906 discard_slab mm/slub.c:3317 [inline] __put_partials+0x130/0x170 mm/slub.c:3864 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:352 kasan_slab_alloc include/linux/kasan.h:252 [inline] slab_post_alloc_hook mm/slub.c:4962 [inline] slab_alloc_node mm/slub.c:5272 [inline] kmem_cache_alloc_noprof+0x250/0x6e0 mm/slub.c:5279 getname_flags.part.0+0x4c/0x550 fs/namei.c:146 getname_flags+0x93/0xf0 include/linux/audit.h:345 getname include/linux/fs.h:2922 [inline] getname_maybe_null include/linux/fs.h:2929 [inline] getname_maybe_null include/linux/fs.h:2926 [inline] vfs_fstatat+0xe1/0xf0 fs/stat.c:370 __do_sys_newfstatat+0x97/0x120 fs/stat.c:542 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff88802b875f00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff88802b875f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88802b876000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ffff88802b876080: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc ffff88802b876100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ================================================================== Tested on: commit: 1c64efcb Merge tag 'rust-rustfmt' of git://git.kernel... git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git console output: https://syzkaller.appspot.com/x/log.txt?x=1166f67c580000 kernel config: https://syzkaller.appspot.com/x/.config?x=f3e7b5a3627a90dd dashboard link: https://syzkaller.appspot.com/bug?extid=2860e75836a08b172755 compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=1069dc58580000