syzbot


KASAN: use-after-free Read in shm_get_unmapped_area

Status: fixed on 2018/05/08 18:30
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+d11f321e7f1923157eac80aa990b446596f46439@syzkaller.appspotmail.com
Fix commit: 3f05317d9889 ipc/shm: fix use-after-free of shm file via remap_file_pages()
First crash: 2454d, last: 2335d
Discussions (6)
Title Replies (including bot) Last reply
[PATCH 3.16 000/366] 3.16.60-rc1 review 370 (370) 2019/03/29 15:47
[PATCH 4.4 00/97] 4.4.129-stable review 111 (111) 2018/05/17 08:54
[PATCH 4.16 000/196] 4.16.4-stable review 213 (213) 2018/04/28 14:59
[PATCH 4.9 00/95] 4.9.96-stable review 120 (120) 2018/04/26 06:46
[PATCH 4.14 000/164] 4.14.36-stable review 172 (172) 2018/04/24 07:25
[PATCH] ipc/shm: fix use-after-free of shm file via remap_file_pages() 10 (10) 2018/04/10 19:28

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in shm_get_unmapped_area+0xfd/0x120 ipc/shm.c:478
Read of size 8 at addr ffff8801bd6ccce8 by task syz-executor3/6565

CPU: 1 PID: 6565 Comm: syz-executor3 Not tainted 4.15.0+ #290
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 shm_get_unmapped_area+0xfd/0x120 ipc/shm.c:478
 get_unmapped_area+0x18d/0x300 mm/mmap.c:2115
 do_mmap+0x2aa/0xe00 mm/mmap.c:1364
 do_mmap_pgoff include/linux/mm.h:2223 [inline]
 SYSC_remap_file_pages mm/mmap.c:2846 [inline]
 SyS_remap_file_pages+0x7ce/0xb30 mm/mmap.c:2762
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453299
RSP: 002b:00007f225d2c3c58 EFLAGS: 00000212 ORIG_RAX: 00000000000000d8
RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 0000000000453299
RDX: 0000000000000000 RSI: 0000000000001000 RDI: 0000000020002000
RBP: 0000000000000450 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f5820
R13: 00000000ffffffff R14: 00007f225d2c46d4 R15: 0000000000000000

Allocated by task 6557:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3540
 kmem_cache_zalloc include/linux/slab.h:678 [inline]
 get_empty_filp+0xfb/0x4f0 fs/file_table.c:122
 alloc_file+0x26/0x390 fs/file_table.c:163
 __shmem_file_setup+0x54f/0x6a0 mm/shmem.c:4230
 shmem_kernel_file_setup+0x32/0x40 mm/shmem.c:4256
 newseg+0x7bd/0xcb0 ipc/shm.c:589
 ipcget_new ipc/util.c:311 [inline]
 ipcget+0x8f0/0xfd0 ipc/util.c:649
 SYSC_shmget ipc/shm.c:675 [inline]
 SyS_shmget+0x158/0x230 ipc/shm.c:659
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 7:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3484 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3742
 file_free_rcu+0x5c/0x70 fs/file_table.c:49
 __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2674 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2900 [inline]
 rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2917
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801bd6cccc0
 which belongs to the cache filp of size 456
The buggy address is located 40 bytes inside of
 456-byte region [ffff8801bd6cccc0, ffff8801bd6cce88)
The buggy address belongs to the page:
page:ffffea0006f5b300 count:1 mapcount:0 mapping:ffff8801bd6cc040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bd6cc040 0000000000000000 0000000100000006
raw: ffffea0006f57760 ffffea0006f5b460 ffff8801da9d2180 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bd6ccb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bd6ccc00: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801bd6ccc80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801bd6ccd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bd6ccd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (19):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/02/01 13:10 upstream 255442c93843 02553e22 .config console log report ci-upstream-kasan-gce
2018/01/29 03:12 upstream 24b1cccf9229 08d47756 .config console log report ci-upstream-kasan-gce
2018/01/28 01:22 upstream c4e0ca7fa241 08146b1a .config console log report ci-upstream-kasan-gce
2018/01/23 22:55 upstream 1995266727fa a5b7566c .config console log report ci-upstream-kasan-gce
2018/01/19 06:07 upstream dda3e15231b3 161c1d64 .config console log report ci-upstream-kasan-gce
2018/01/15 07:50 upstream 9443c168505d 66d492a6 .config console log report ci-upstream-kasan-gce
2018/01/06 20:46 upstream 3219e264b984 053171ea .config console log report ci-upstream-kasan-gce
2017/12/30 14:52 upstream 5aa90a845892 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/18 18:59 upstream 1291a0d5049d 1c4160ef .config console log report ci-upstream-kasan-gce
2018/01/22 07:11 linux-next 761914dd2975 fbbdcd92 .config console log report ci-upstream-next-kasan-gce
2018/01/20 22:02 linux-next 761914dd2975 fbbdcd92 .config console log report ci-upstream-next-kasan-gce
2018/01/07 11:37 linux-next 990b6a07d18c 19c05fff .config console log report ci-upstream-next-kasan-gce
2018/01/06 11:23 linux-next 990b6a07d18c 00193447 .config console log report ci-upstream-next-kasan-gce
2018/01/04 10:34 linux-next 73005e1a35fd 00193447 .config console log report ci-upstream-next-kasan-gce
2017/11/21 18:01 linux-next aa1fbe633d30 d4d14b03 .config console log report ci-upstream-next-kasan-gce
2017/10/26 16:29 linux-next 36ef71cae353 e511d9f8 .config console log report ci-upstream-next-kasan-gce
2017/10/26 13:15 linux-next 36ef71cae353 e511d9f8 .config console log report ci-upstream-next-kasan-gce
2017/10/10 03:40 linux-next 49827b977a2e 441d64d9 .config console log report ci-upstream-next-kasan-gce
2017/10/04 22:18 linux-next 1418b852174a c26ea367 .config console log report ci-upstream-next-kasan-gce
* Struck through repros no longer work on HEAD.