syzbot


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

Status: upstream: reported on 2025/10/12 09:24
Reported-by: syzbot+1cf51b6632b24303a322@syzkaller.appspotmail.com
First crash: 52d, last: 44d
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in kernfs_find_ns kernfs 2 2 1465d 1460d 0/29 auto-closed as invalid on 2022/03/29 00:22
android-54 general protection fault in kernfs_find_ns 2 1 1657d 1657d 0/2 auto-closed as invalid on 2021/09/18 09:16
android-5-10 general protection fault in kernfs_find_ns 2 C error 13 1d14h 815d 0/2 upstream: reported C repro on 2023/09/09 18:30
linux-5.15 KASAN: global-out-of-bounds Read in kernfs_find_ns 17 1 186d 186d 0/3 auto-obsoleted due to no activity on 2025/09/08 00:48
android-54 general protection fault in kernfs_find_ns (2) 2 C 21 246d 1500d 0/2 upstream: reported C repro on 2021/10/24 20:02

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in kernfs_name_compare fs/kernfs/dir.c:326 [inline]
BUG: KASAN: slab-out-of-bounds in kernfs_find_ns+0x473/0x510 fs/kernfs/dir.c:827
Read of size 4 at addr ffff88802540a8a0 by task syz.2.2430/15107

CPU: 1 PID: 15107 Comm: syz.2.2430 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 kernfs_name_compare fs/kernfs/dir.c:326 [inline]
 kernfs_find_ns+0x473/0x510 fs/kernfs/dir.c:827
 kernfs_remove_by_name_ns+0x37/0x100 fs/kernfs/dir.c:1563
 remove_bind_files drivers/base/bus.c:550 [inline]
 bus_remove_driver+0x89/0x230 drivers/base/bus.c:674
 comedi_device_detach_locked+0x16e/0x710 drivers/comedi/drivers.c:207
 do_devconfig_ioctl drivers/comedi/comedi_fops.c:844 [inline]
 comedi_unlocked_ioctl+0xd0b/0x1050 drivers/comedi/comedi_fops.c:2173
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7feb22792fc9
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:00007feb209b8038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007feb229ea180 RCX: 00007feb22792fc9
RDX: 0000000000000000 RSI: 0000000040946400 RDI: 0000000000000007
RBP: 00007feb22815f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007feb229ea218 R14: 00007feb229ea180 R15: 00007ffedb7ba018
 </TASK>

Allocated by task 12361:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xb5/0xf0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 uevent_net_init+0xc3/0x2b0 lib/kobject_uevent.c:781
 ops_init+0x357/0x600 net/core/net_namespace.c:138
 setup_net+0x38d/0x9f0 net/core/net_namespace.c:333
 copy_net_ns+0x348/0x5b0 net/core/net_namespace.c:503
 create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x116/0x160 kernel/nsproxy.c:226
 ksys_unshare+0x4bc/0x890 kernel/fork.c:3175
 __do_sys_unshare kernel/fork.c:3249 [inline]
 __se_sys_unshare kernel/fork.c:3247 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3247
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88802540a880
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes to the right of
 32-byte region [ffff88802540a880, ffff88802540a8a0)
The buggy address belongs to the page:
page:ffffea0000950280 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2540a
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888016841500
raw: 0000000000000000 0000000000400040 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 0x112c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 4472, ts 866817845718, free_ts 866778079755
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x81e/0xdf0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc+0x1cd/0x330 mm/slub.c:4408
 kmalloc include/linux/slab.h:612 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
 tomoyo_encode+0x27e/0x540 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x5cd/0x610 security/tomoyo/realpath.c:288
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x183/0x360 security/tomoyo/file.c:771
 security_file_open+0x5e/0xa0 security/security.c:1668
 do_dentry_open+0x322/0xf80 fs/open.c:813
 do_open fs/namei.c:3616 [inline]
 path_openat+0x2682/0x2f30 fs/namei.c:3750
 do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
 do_sys_openat2+0x142/0x4a0 fs/open.c:1253
 do_sys_open fs/open.c:1269 [inline]
 __do_sys_openat fs/open.c:1285 [inline]
 __se_sys_openat fs/open.c:1280 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1280
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x94/0x280 mm/page_alloc.c:3396
 tlb_batch_list_free mm/mmu_gather.c:61 [inline]
 tlb_finish_mmu+0x236/0x2e0 mm/mmu_gather.c:341
 exit_mmap+0x3a6/0x5f0 mm/mmap.c:3218
 __mmput+0x115/0x3b0 kernel/fork.c:1127
 exit_mm+0x567/0x6c0 kernel/exit.c:550
 do_exit+0x5a1/0x20a0 kernel/exit.c:870
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 get_signal+0x6ca/0x12c0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff88802540a780: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88802540a800: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
>ffff88802540a880: 00 00 00 fc fc fc fc fc fa fb fb fb fc fc fc fc
                               ^
 ffff88802540a900: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88802540a980: 00 00 00 fc fc fc fc fc 00 00 00 fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/20 00:38 linux-5.15.y ac56c046adf4 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in kernfs_find_ns
2025/10/12 09:23 linux-5.15.y 29e53a5b1c4f ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in kernfs_find_ns
* Struck through repros no longer work on HEAD.