syzbot


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

Status: fixed on 2018/08/28 17:48
Subsystems: autofs
[Documentation on labels]
Reported-by: syzbot+87c3c541582e56943277@syzkaller.appspotmail.com
Fix commit: 0633da48f079 autofs: fix autofs_sbi() does not check super block type
First crash: 2172d, last: 2167d
Discussions (6)
Title Replies (including bot) Last reply
[PATCH 4.14 000/126] 4.14.71-stable review 137 (137) 2018/11/29 15:07
[PATCH 4.18 000/158] 4.18.9-stable review 163 (163) 2018/09/18 17:33
[PATCH 4.4 00/56] 4.4.157-stable review 60 (60) 2018/09/18 16:56
[PATCH 4.9 00/70] 4.9.128-stable review 74 (74) 2018/09/18 16:54
[PATCH] autofs - fix autofs_sbi() does not check super block type 3 (3) 2018/08/29 06:35
KASAN: slab-out-of-bounds Read in _autofs_dev_ioctl 0 (1) 2018/08/15 08:10
Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-49 KASAN: slab-out-of-bounds Read in _autofs_dev_ioctl C 1 2172d 1926d 0/3 public: reported C repro on 2019/04/14 08:51

Sample crash report:
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KASAN: slab-out-of-bounds in _autofs_dev_ioctl+0x8f5/0x990 fs/autofs/dev-ioctl.c:670
Read of size 4 at addr ffff8801aced2d00 by task syz-executor356/4406

CPU: 1 PID: 4406 Comm: syz-executor356 Not tainted 4.18.0-rc8+ #183
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 _autofs_dev_ioctl+0x8f5/0x990 fs/autofs/dev-ioctl.c:670
 autofs_dev_ioctl+0x1b/0x30 fs/autofs/dev-ioctl.c:704
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:684
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
 __do_sys_ioctl fs/ioctl.c:708 [inline]
 __se_sys_ioctl fs/ioctl.c:706 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440139
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007ffddd407408 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440139
RDX: 0000000020000180 RSI: 800000000000937e RDI: 0000000000000005
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004019c0
R13: 0000000000401a50 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 4406:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
 kmalloc include/linux/slab.h:513 [inline]
 kzalloc include/linux/slab.h:707 [inline]
 ramfs_fill_super+0xc4/0x580 fs/ramfs/inode.c:226
 mount_nodev+0x6b/0x110 fs/super.c:1220
 ramfs_mount+0x2c/0x40 fs/ramfs/inode.c:253
 mount_fs+0xae/0x328 fs/super.c:1277
 vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
 vfs_kern_mount fs/namespace.c:1027 [inline]
 do_new_mount fs/namespace.c:2518 [inline]
 do_mount+0x581/0x30e0 fs/namespace.c:2848
 ksys_mount+0x12d/0x140 fs/namespace.c:3064
 __do_sys_mount fs/namespace.c:3078 [inline]
 __se_sys_mount fs/namespace.c:3075 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2740:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x260 mm/slab.c:3813
 single_release+0x8f/0xb0 fs/seq_file.c:609
 __fput+0x355/0x8b0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:192 [inline]
 exit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801aced2d00
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff8801aced2d00, ffff8801aced2d20)
The buggy address belongs to the page:
page:ffffea0006b3b480 count:1 mapcount:0 mapping:ffff8801dac001c0 index:0xffff8801aced2fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007664788 ffffea00076b0308 ffff8801dac001c0
raw: ffff8801aced2fc1 ffff8801aced2000 0000000100000018 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801aced2c00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801aced2c80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8801aced2d00: 02 fc fc fc fc fc fc fc 00 fc fc fc fc fc fc fc
                   ^
 ffff8801aced2d80: 00 00 fc fc fc fc fc fc 00 00 fc fc fc fc fc fc
 ffff8801aced2e00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/08/11 09:23 upstream f313b43be461 7a88b141 .config console log report syz C ci-upstream-kasan-gce-root
2018/08/11 09:00 upstream f313b43be461 7a88b141 .config console log report syz C ci-upstream-kasan-gce
2018/08/11 09:22 upstream f313b43be461 7a88b141 .config console log report syz C ci-upstream-kasan-gce-386
2018/08/16 07:40 linux-next 3070c752f222 9ccc1d45 .config console log report syz C ci-upstream-linux-next-kasan-gce-root
2018/08/11 07:03 upstream f313b43be461 7a88b141 .config console log report ci-upstream-kasan-gce
* Struck through repros no longer work on HEAD.