syzbot


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

Status: fixed on 2018/01/11 01:23
Subsystems: lsm
[Documentation on labels]
Reported-by: syzbot+7bf52949a1cf3a36b620@syzkaller.appspotmail.com
Fix commit: dc32b5c3e6e2 capabilities: fix buffer overread on very short xattr
First crash: 2339d, last: 2331d
Discussions (1)
Title Replies (including bot) Last reply
KASAN: slab-out-of-bounds Read in cap_convert_nscap 1 (2) 2018/01/02 17:00

Sample crash report:
audit: type=1400 audit(1514656959.329:7): avc:  denied  { map } for  pid=3194 comm="syzkaller150350" path="/root/syzkaller150350154" dev="sda1" ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: slab-out-of-bounds in cap_convert_nscap+0x501/0x610 security/commoncap.c:498
Read of size 4 at addr ffff8801c61c7280 by task syzkaller150350/3194

CPU: 0 PID: 3194 Comm: syzkaller150350 Not tainted 4.15.0-rc5+ #242
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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 cap_convert_nscap+0x501/0x610 security/commoncap.c:498
 setxattr+0x365/0x400 fs/xattr.c:446
 SYSC_fsetxattr fs/xattr.c:508 [inline]
 SyS_fsetxattr+0x130/0x190 fs/xattr.c:497
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x43fcf9
RSP: 002b:00007ffdc0d4c408 EFLAGS: 00000203 ORIG_RAX: 00000000000000be
RAX: ffffffffffffffda RBX: 6f72746e6f632f2e RCX: 000000000043fcf9
RDX: 00000000208c4fe9 RSI: 0000000020f4c000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000203 R12: 0000000000401660
R13: 00000000004016f0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3194:
 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
 __do_kmalloc_node mm/slab.c:3672 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3679
 kmalloc_node include/linux/slab.h:541 [inline]
 kvmalloc_node+0x99/0xd0 mm/util.c:397
 kvmalloc include/linux/mm.h:541 [inline]
 setxattr+0x152/0x400 fs/xattr.c:435
 SYSC_fsetxattr fs/xattr.c:508 [inline]
 SyS_fsetxattr+0x130/0x190 fs/xattr.c:497
 entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 1679:
 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:3488 [inline]
 kfree+0xd6/0x260 mm/slab.c:3803
 kfree_link+0x15/0x20 fs/libfs.c:1066
 do_delayed_call include/linux/delayed_call.h:28 [inline]
 put_link fs/namei.c:898 [inline]
 step_into fs/namei.c:1746 [inline]
 walk_component+0x54d/0x13d0 fs/namei.c:1803
 link_path_walk+0x6a9/0x1470 fs/namei.c:2110
 path_openat+0x2bc/0x3530 fs/namei.c:3519
 do_filp_open+0x25b/0x3b0 fs/namei.c:3554
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801c61c7280
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff8801c61c7280, ffff8801c61c72a0)
The buggy address belongs to the page:
page:0000000077f4e811 count:1 mapcount:0 mapping:000000007008f3c4 index:0xffff8801c61c7fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c61c7000 ffff8801c61c7fc1 000000010000003f
raw: ffffea000718a160 ffffea00071875a0 ffff8801dac001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c61c7180: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801c61c7200: fb fb fb fb fc fc fc fc 00 00 00 fc fc fc fc fc
>ffff8801c61c7280: 01 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
                   ^
 ffff8801c61c7300: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801c61c7380: fb fb fb fb fc fc fc fc 00 00 01 fc fc fc fc fc
==================================================================

Crashes (4148):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2017/12/30 18:04 upstream 5aa90a845892 bb6384b8 .config console log report syz C ci-upstream-kasan-gce
2017/12/29 09:44 upstream 2758b3e3e630 7d240098 .config console log report syz C ci-upstream-kasan-gce
2017/12/30 13:06 upstream 5aa90a845892 bb6384b8 .config console log report syz C ci-upstream-kasan-gce-386
2017/12/29 09:25 upstream 2758b3e3e630 7d240098 .config console log report syz C ci-upstream-kasan-gce-386
2017/12/30 21:37 linux-next 0e08c463db38 bb6384b8 .config console log report syz C ci-upstream-next-kasan-gce
2017/12/30 12:58 mmots 37759fa6d0fa bb6384b8 .config console log report syz C ci-upstream-mmots-kasan-gce
2017/12/29 09:44 mmots 37759fa6d0fa 7d240098 .config console log report syz C ci-upstream-mmots-kasan-gce
2017/12/29 09:44 linux-next 0e08c463db38 7d240098 .config console log report syz C ci-upstream-next-kasan-gce
2017/12/31 05:58 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:54 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:45 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:43 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:35 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:33 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:25 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:23 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:14 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:07 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 04:58 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce
2017/12/31 05:44 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 05:28 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 05:26 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 05:24 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 05:22 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 05:17 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 05:12 upstream 71ee203389f7 bb6384b8 .config console log report ci-upstream-kasan-gce-386
2017/12/31 12:50 linux-next 0e08c463db38 00193447 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:59 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:51 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:51 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:48 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:44 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:42 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:42 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:40 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:35 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:29 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:24 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:23 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:22 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:21 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:19 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:08 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 05:04 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 05:04 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
2017/12/31 04:59 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 04:59 mmots 37759fa6d0fa bb6384b8 .config console log report ci-upstream-mmots-kasan-gce
2017/12/31 04:59 linux-next 0e08c463db38 bb6384b8 .config console log report ci-upstream-next-kasan-gce
* Struck through repros no longer work on HEAD.