Subject: KASAN: slab-out-of-bounds Read in sctp_getsockopt

From: syzbot <[email-masked]>
Date: Fri, 26 Oct 2018 09:38:04 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    bd6bf7c10484 Merge tag 'pci-v4.20-changes' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16fd6bcb400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2dd8629d56664133
dashboard link: https://syzkaller.appspot.com/bug?extid=5da0d0a72a9e7d791748
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16b3ea33400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17f9f1bd400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: slab-out-of-bounds in sctp_getsockopt_pr_streamstatus  
net/sctp/socket.c:7174 [inline]
BUG: KASAN: slab-out-of-bounds in sctp_getsockopt+0x7516/0x7cc2  
net/sctp/socket.c:7582
Read of size 8 at addr ffff8801d89f0968 by task syz-executor278/5330

CPU: 1 PID: 5330 Comm: syz-executor278 Not tainted 4.19.0+ #303
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+0x244/0x39d lib/dump_stack.c:113
  print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  sctp_getsockopt_pr_streamstatus net/sctp/socket.c:7174 [inline]
  sctp_getsockopt+0x7516/0x7cc2 net/sctp/socket.c:7582
  sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2937
  __sys_getsockopt+0x1ad/0x390 net/socket.c:1939
  __do_sys_getsockopt net/socket.c:1950 [inline]
  __se_sys_getsockopt net/socket.c:1947 [inline]
  __x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445789
Code: e8 6c b6 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 2b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007effdb293db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00000000006dac48 RCX: 0000000000445789
RDX: 0000000000000074 RSI: 0000000000000084 RDI: 0000000000000003
RBP: 00000000006dac40 R08: 0000000020000040 R09: 0000000000000000
R10: 0000000020000080 R11: 0000000000000246 R12: 00000000006dac4c
R13: 00007ffcfc408c6f R14: 00007effdb2949c0 R15: 00000000006dad2c

Allocated by task 5329:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
  kmalloc include/linux/slab.h:513 [inline]
  kzalloc include/linux/slab.h:707 [inline]
  sctp_stream_init_ext+0x4f/0xf0 net/sctp/stream.c:237
  sctp_sendmsg_to_asoc+0x1308/0x1a20 net/sctp/socket.c:1896
  sctp_sendmsg+0x13c2/0x1da0 net/sctp/socket.c:2113
  inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:621 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:631
  __sys_sendto+0x3d7/0x670 net/socket.c:1788
  __do_sys_sendto net/socket.c:1800 [inline]
  __se_sys_sendto net/socket.c:1796 [inline]
  __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 3223:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xcf/0x230 mm/slab.c:3813
  kzfree+0x28/0x30 mm/slab_common.c:1543
  aa_free_file_ctx security/apparmor/include/file.h:76 [inline]
  apparmor_file_free_security+0x133/0x1a0 security/apparmor/lsm.c:448
  security_file_free+0x4a/0x80 security/security.c:900
  file_free fs/file_table.c:54 [inline]
  __fput+0x4e8/0xa30 fs/file_table.c:294
  ____fput+0x15/0x20 fs/file_table.c:309
  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x318/0x380 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 ffff8801d89f0900
  which belongs to the cache kmalloc-96 of size 96
The buggy address is located 8 bytes to the right of
  96-byte region [ffff8801d89f0900, ffff8801d89f0960)
The buggy address belongs to the page:
page:ffffea0007627c00 count:1 mapcount:0 mapping:ffff8801da8004c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007646748 ffffea0007613488 ffff8801da8004c0
raw: 0000000000000000 ffff8801d89f0000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d89f0800: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
  ffff8801d89f0880: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ffff8801d89f0900: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
                                                           ^
  ffff8801d89f0980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
  ffff8801d89f0a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================

---
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