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KASAN: use-after-free Read in nr_add_node (2)

Status: upstream: reported C repro on 2025/09/18 05:54
Reported-by: syzbot+b0577df3f3dba9fee55a@syzkaller.appspotmail.com
First crash: 14h15m, last: 14h15m
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in nr_add_node 19 1 191d 191d 0/3 auto-obsoleted due to no activity on 2025/06/19 16:48
linux-5.15 KASAN: use-after-free Read in nr_add_node origin:upstream 19 C error 1 51d 239d 0/3 upstream: reported C repro on 2025/01/22 09:11
linux-6.6 KASAN: slab-use-after-free Read in nr_add_node 19 syz 1 14h46m 14h46m 0/2 upstream: reported syz repro on 2025/09/18 05:23

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in nr_add_node+0x1fc4/0x2120 net/netrom/nr_route.c:248
Read of size 2 at addr ffff0000cc6fc232 by task syz.0.10372/15844

CPU: 0 PID: 15844 Comm: syz.0.10372 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0x100 mm/kasan/report.c:524
 __asan_report_load2_noabort+0x2c/0x38 mm/kasan/report_generic.c:349
 nr_add_node+0x1fc4/0x2120 net/netrom/nr_route.c:248
 nr_rt_ioctl+0x9f8/0xb80 net/netrom/nr_route.c:651
 nr_ioctl+0x1c4/0x4e4 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0xf8/0x240 net/socket.c:1204
 sock_ioctl+0x5c4/0x840 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Allocated by task 15840:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:52
 kasan_save_alloc_info+0x28/0x34 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 kmalloc_trace+0x7c/0x94 mm/slab_common.c:1031
 kmalloc include/linux/slab.h:563 [inline]
 nr_add_node+0x730/0x2120 net/netrom/nr_route.c:146
 nr_rt_ioctl+0x9f8/0xb80 net/netrom/nr_route.c:651
 nr_ioctl+0x1c4/0x4e4 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0xf8/0x240 net/socket.c:1204
 sock_ioctl+0x5c4/0x840 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Freed by task 15844:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:52
 kasan_save_free_info+0x3c/0x60 mm/kasan/generic.c:516
 ____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:236
 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:244
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x16c/0x1ec mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xc0/0x224 mm/slub.c:3700
 kfree+0xd0/0x1ac mm/slab_common.c:988
 nr_neigh_put+0x144/0x1cc include/net/netrom.h:143
 nr_add_node+0x17a4/0x2120 net/netrom/nr_route.c:246
 nr_rt_ioctl+0x9f8/0xb80 net/netrom/nr_route.c:651
 nr_ioctl+0x1c4/0x4e4 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0xf8/0x240 net/socket.c:1204
 sock_ioctl+0x5c4/0x840 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the object at ffff0000cc6fc200
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 50 bytes inside of
 128-byte region [ffff0000cc6fc200, ffff0000cc6fc280)

The buggy address belongs to the physical page:
page:000000003e598c8f refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10c6fc
flags: 0x5ffc00000000200(slab|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000200 fffffc000361ae40 dead000000000003 ffff0000c0002300
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000cc6fc100: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000cc6fc180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000cc6fc200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff0000cc6fc280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000cc6fc300: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Unable to handle kernel paging request at virtual address e0d2408bc00007bc
KASAN: maybe wild-memory-access in range [0x0696045e00003de0-0x0696045e00003de7]
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
[e0d2408bc00007bc] address between user and kernel address ranges
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 15844 Comm: syz.0.10372 Tainted: G    B              syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 02400005 (nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : __hlist_del include/linux/list.h:884 [inline]
pc : hlist_del_init include/linux/list.h:912 [inline]
pc : __nr_remove_neigh net/netrom/nr_route.c:298 [inline]
pc : nr_remove_neigh+0x6c/0xec net/netrom/nr_route.c:308
lr : __hlist_del include/linux/list.h:881 [inline]
lr : hlist_del_init include/linux/list.h:912 [inline]
lr : __nr_remove_neigh net/netrom/nr_route.c:298 [inline]
lr : nr_remove_neigh+0x64/0xec net/netrom/nr_route.c:308
sp : ffff800023c97810
x29: ffff800023c97810 x28: 0000000000010001 x27: 1fffe0001b011343
x26: ffff0000d8089a50 x25: 0000000000000000 x24: ffff0000d8089a1f
x23: 1fffe0001b011348 x22: dfff800000000000 x21: 0000000000000000
x20: 0696045e00003de4 x19: ffff0000cc6fc200 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082e7648 x15: 0000000000000000
x14: 00000000ffffffff x13: 0000000000000001 x12: ffff700004792ee8
x11: 1ffff00004792ee8 x10: 0000000000000004 x9 : ffff80001c327a10
x8 : 00d2c08bc00007bc x7 : 0000000000000001 x6 : ffff800010ac9680
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff800010ac96b4
x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000000
Call trace:
 __hlist_del include/linux/list.h:881 [inline]
 hlist_del_init include/linux/list.h:912 [inline]
 __nr_remove_neigh net/netrom/nr_route.c:298 [inline]
 nr_remove_neigh+0x6c/0xec net/netrom/nr_route.c:308
 nr_add_node+0x197c/0x2120 net/netrom/nr_route.c:249
 nr_rt_ioctl+0x9f8/0xb80 net/netrom/nr_route.c:651
 nr_ioctl+0x1c4/0x4e4 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0xf8/0x240 net/socket.c:1204
 sock_ioctl+0x5c4/0x840 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: aa1303e0 97d4996a d343fe88 f9400275 (38766908) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	aa1303e0 	mov	x0, x19
   4:	97d4996a 	bl	0xffffffffff5265ac
   8:	d343fe88 	lsr	x8, x20, #3
   c:	f9400275 	ldr	x21, [x19]
* 10:	38766908 	ldrb	w8, [x8, x22] <-- trapping instruction

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/18 05:53 linux-6.1.y 3db754f56897 e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nr_add_node
* Struck through repros no longer work on HEAD.