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

Status: upstream: reported C repro on 2025/10/30 14:44
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+4c60b7f9682fa6e32a40@syzkaller.appspotmail.com
First crash: 301d, last: 227d
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: KASAN: slab-out-of-bounds Read in udf_get_fileshortad (log)
Repro: C syz .config
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/11/07 linux-6.1.y (ToT) f6e38ae624cf C [report] KASAN: slab-out-of-bounds Read in udf_get_fileshortad
2025/11/07 upstream (ToT) 4a0c9b339199 C Didn't crash
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KMSAN: uninit-value in udf_get_fileshortad udf 7 syz, C 3 697d 709d 28/29 fixed on 2024/11/12 23:31
upstream KASAN: use-after-free Read in udf_get_fileshortad udf 19 1 594d 590d 0/29 auto-obsoleted due to no activity on 2025/04/10 22:21
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2026/04/26 11:44 13m fix candidate upstream error job log
2026/03/27 10:23 1m fix candidate upstream error job log
2026/02/24 09:23 4m fix candidate upstream error job log
2026/01/23 23:54 1m fix candidate upstream error job log
2026/01/12 21:07 2h44m bisect fix linux-6.1.y OK (0) job log log
2025/12/10 11:22 1h22m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
RBP: 00007f4c67611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4c677e5fa0 R14: 00007f4c677e5fa0 R15: 0000000000000002
 </TASK>
==================================================================
BUG: KASAN: slab-out-of-bounds in udf_get_fileshortad+0x152/0x1a0 fs/udf/directory.c:497
Read of size 4 at addr ffff88801ee4cf38 by task syz.0.17/4426

CPU: 1 PID: 4426 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 udf_get_fileshortad+0x152/0x1a0 fs/udf/directory.c:497
 udf_current_aext+0x43a/0xb00 fs/udf/inode.c:2122
 udf_next_aext+0x101/0x450 fs/udf/inode.c:2057
 udf_extend_file fs/udf/inode.c:549 [inline]
 udf_setsize+0x9f7/0x1090 fs/udf/inode.c:1147
 udf_setattr+0x404/0x560 fs/udf/file.c:279
 notify_change+0xc74/0xf40 fs/attr.c:499
 do_truncate+0x197/0x220 fs/open.c:65
 vfs_truncate+0x262/0x2f0 fs/open.c:111
 do_sys_truncate+0xdc/0x190 fs/open.c:134
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4c6758efc9
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:00007ffde0944bf8 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f4c677e5fa0 RCX: 00007f4c6758efc9
RDX: 0000000000000000 RSI: 000000404000f000 RDI: 0000200000000080
RBP: 00007f4c67611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4c677e5fa0 R14: 00007f4c677e5fa0 R15: 0000000000000002
 </TASK>

Allocated by task 4385:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc+0xb0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 neigh_alloc net/core/neighbour.c:495 [inline]
 ___neigh_create+0x6ce/0x24c0 net/core/neighbour.c:649
 ip6_finish_output2+0x14f0/0x1590 net/ipv6/ip6_output.c:129
 dst_output include/net/dst.h:453 [inline]
 NF_HOOK include/linux/netfilter.h:302 [inline]
 ndisc_send_skb+0xbfb/0x1510 net/ipv6/ndisc.c:513
 ndisc_send_ns+0xc8/0x150 net/ipv6/ndisc.c:671
 addrconf_dad_work+0xa15/0x14d0 net/ipv6/addrconf.c:4219
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff88801ee4c800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 824 bytes to the right of
 1024-byte region [ffff88801ee4c800, ffff88801ee4cc00)

The buggy address belongs to the physical page:
page:ffffea00007b9200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ee48
head:ffffea00007b9200 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea000082de00 dead000000000002 ffff888017441dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3949, tgid 3949 (dhcpcd), ts 33529695024, free_ts 33486061819
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
 alloc_slab_page+0x5d/0x160 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2c0 mm/slub.c:1997
 ___slab_alloc+0xbc6/0x1230 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x1a0/0x260 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 load_elf_phdrs+0x132/0x230 fs/binfmt_elf.c:507
 load_elf_binary+0x955/0x26d0 fs/binfmt_elf.c:987
 search_binary_handler fs/exec.c:1764 [inline]
 exec_binprm fs/exec.c:1805 [inline]
 bprm_execve+0xb10/0x18a0 fs/exec.c:1874
 do_execveat_common+0x51b/0x6c0 fs/exec.c:1979
 do_execve fs/exec.c:2053 [inline]
 __do_sys_execve fs/exec.c:2129 [inline]
 __se_sys_execve fs/exec.c:2124 [inline]
 __x64_sys_execve+0x8e/0xa0 fs/exec.c:2124
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3479
 free_slab mm/slub.c:2036 [inline]
 discard_slab mm/slub.c:2042 [inline]
 __unfreeze_partials+0x1a5/0x200 mm/slub.c:2591
 put_cpu_partial+0x17c/0x250 mm/slub.c:2667
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x123/0x2f0 mm/slub.c:3383
 vm_area_dup+0x23/0x1a0 kernel/fork.c:467
 __split_vma+0xb9/0x500 mm/mmap.c:2363
 mprotect_fixup+0x597/0x7f0 mm/mprotect.c:623
 do_mprotect_pkey+0x754/0xa40 mm/mprotect.c:792
 __do_sys_mprotect mm/mprotect.c:819 [inline]
 __se_sys_mprotect mm/mprotect.c:816 [inline]
 __x64_sys_mprotect+0x7c/0x90 mm/mprotect.c:816
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88801ee4ce00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88801ee4ce80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801ee4cf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                        ^
 ffff88801ee4cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88801ee4d000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/30 16:02 linux-6.1.y f6e38ae624cf fd2207e7 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in udf_get_fileshortad
2025/10/30 15:24 linux-6.1.y f6e38ae624cf fd2207e7 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in udf_get_fileshortad
2025/10/30 14:43 linux-6.1.y f6e38ae624cf fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in udf_get_fileshortad
* Struck through repros no longer work on HEAD.