KASAN: slab-out-of-bounds Write in __put_unused_fd

Status: fixed on 2025/05/06 15:33
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+6a3aa63412255587b21b@syzkaller.appspotmail.com
Fix commit: 0c0214df28f0 fanotify: Fix crash in fanotify_init(2)
First crash: 572d, last: 567d
Cause bisection: introduced by (bisect log) :
commit ebe559609d7829b52c6642b581860760984faf9d
Author: Al Viro <viro@zeniv.linux.org.uk>
Date: Fri Nov 15 15:30:14 2024 +0000

  fs: get rid of __FMODE_NONOTIFY kludge

Crash: KASAN: use-after-free Write in put_unused_fd (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [fs?] KASAN: slab-out-of-bounds Write in __put_unused_fd 3 (8) 2025/01/06 11:49
▶ ▼ Last patch testing requests (4)
Created Duration User Patch Repo Result
2025/01/06 11:15 32m jack@suse.cz git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next OK log
2025/01/01 01:35 27m hdanton@sina.com patch linux-next OK log
2024/12/31 13:32 0m eric.dumazet@gmail.com patch linux-next error
2024/12/31 13:04 35m edumazet@google.com patch linux-next OK log

Sample crash report:
RAX: ffffffffffffffda RBX: 00007ffd163c2680 RCX: 00007f8b75a4d669
RDX: 00007f8b75a4c8a0 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000001 R08: 00007ffd163c2407 R09: 00000000000000a0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>
==================================================================
BUG: KASAN: use-after-free in instrument_write include/linux/instrumented.h:40 [inline]
BUG: KASAN: use-after-free in ___clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:44 [inline]
BUG: KASAN: use-after-free in __clear_open_fd fs/file.c:324 [inline]
BUG: KASAN: use-after-free in __put_unused_fd+0xdb/0x2a0 fs/file.c:600
Write of size 8 at addr ffff88804952aa48 by task syz-executor128/5830

CPU: 1 UID: 0 PID: 5830 Comm: syz-executor128 Not tainted 6.13.0-rc3-next-20241220-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 instrument_write include/linux/instrumented.h:40 [inline]
 ___clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:44 [inline]
 __clear_open_fd fs/file.c:324 [inline]
 __put_unused_fd+0xdb/0x2a0 fs/file.c:600
 put_unused_fd+0x5c/0x70 fs/file.c:609
 __do_sys_fanotify_init fs/notify/fanotify/fanotify_user.c:1628 [inline]
 __se_sys_fanotify_init+0x800/0x970 fs/notify/fanotify/fanotify_user.c:1466
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8b75a4d669
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd163c2668 EFLAGS: 00000246 ORIG_RAX: 000000000000012c
RAX: ffffffffffffffda RBX: 00007ffd163c2680 RCX: 00007f8b75a4d669
RDX: 00007f8b75a4c8a0 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000001 R08: 00007ffd163c2407 R09: 00000000000000a0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4952a
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL), pid 1, tgid 1 (swapper/0), ts 21408968854, free_ts 21922910177
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 split_free_pages+0xe1/0x2d0 mm/page_alloc.c:6374
 alloc_contig_range_noprof+0x10eb/0x1770 mm/page_alloc.c:6551
 __alloc_contig_pages mm/page_alloc.c:6581 [inline]
 alloc_contig_pages_noprof+0x4b3/0x5c0 mm/page_alloc.c:6663
 debug_vm_pgtable_alloc_huge_page+0xaf/0x100 mm/debug_vm_pgtable.c:1084
 init_args+0x83b/0xb20 mm/debug_vm_pgtable.c:1266
 debug_vm_pgtable+0xe0/0x550 mm/debug_vm_pgtable.c:1304
 do_one_initcall+0x248/0x870 init/main.c:1267
 do_initcall_level+0x157/0x210 init/main.c:1329
 do_initcalls+0x3f/0x80 init/main.c:1345
 kernel_init_freeable+0x435/0x5d0 init/main.c:1578
 kernel_init+0x1d/0x2b0 init/main.c:1467
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_frozen_pages+0xe0d/0x10e0 mm/page_alloc.c:2660
 free_contig_range+0x14c/0x430 mm/page_alloc.c:6697
 destroy_args+0x92/0x910 mm/debug_vm_pgtable.c:1017
 debug_vm_pgtable+0x4be/0x550 mm/debug_vm_pgtable.c:1397
 do_one_initcall+0x248/0x870 init/main.c:1267
 do_initcall_level+0x157/0x210 init/main.c:1329
 do_initcalls+0x3f/0x80 init/main.c:1345
 kernel_init_freeable+0x435/0x5d0 init/main.c:1578
 kernel_init+0x1d/0x2b0 init/main.c:1467
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffff88804952a900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804952a980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88804952aa00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88804952aa80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804952ab00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/12/30 01:06 linux-next 8155b4ef3466 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Write in __put_unused_fd
2024/12/30 00:22 linux-next 8155b4ef3466 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Write in __put_unused_fd
2024/12/29 23:42 linux-next 8155b4ef3466 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Write in __put_unused_fd
2024/12/29 23:01 linux-next 8155b4ef3466 d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-out-of-bounds Write in __put_unused_fd
2025/01/04 07:34 linux-next 8155b4ef3466 f3558dbf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Write in __put_unused_fd
* Struck through repros no longer work on HEAD.