Subject: KASAN: stack-out-of-bounds Read in bpf_tcp_close

From: syzbot <[email-masked]>
Date: Wed, 18 Jul 2018 15:19:02 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    8ae71e76cf1f Merge branch 'bpf-offload-sharing'
git tree:       bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1379a978400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=89129667b46496c3
dashboard link: https://syzkaller.appspot.com/bug?extid=65a97319fd875ea52b73
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=114f4b2c400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1774932c400000

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

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
IPVS: ftp: loaded support on port[0] = 21
==================================================================
swap_info_get: Bad swap file entry 8007fffc400d72b
BUG: KASAN: stack-out-of-bounds in __read_once_size  
include/linux/compiler.h:188 [inline]
BUG: KASAN: stack-out-of-bounds in smap_psock_sk kernel/bpf/sockmap.c:149  
[inline]
BUG: KASAN: stack-out-of-bounds in bpf_tcp_close+0xf10/0x1050  
kernel/bpf/sockmap.c:316
Read of size 8 at addr ffff8801adcc4428 by task syz-executor115/24313
BUG: Bad page map in process syz-executor115  pte:1ffff10035cac810  
pmd:1ae564067

CPU: 0 PID: 24313 Comm: syz-executor115 Not tainted 4.18.0-rc3+ #58
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:

addr:(____ptrval____) vm_flags:00000875 anon_vma:          (null)  
mapping:(____ptrval____) index:0
Allocated by task 2294230744:
usercopy: Kernel memory overwrite attempt detected to SLAB  
object 'task_struct(17:syz0)' (offset 6088, size 2)!
file:syz-executor115250413 fault:ext4_filemap_fault mmap:ext4_file_mmap  
readpage:ext4_readpage
------------[ cut here ]------------
Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected  
to SLAB object 'task_struct(17:syz0)' (offset 4936, size 2)!
WARNING: CPU: 0 PID: 24313 at mm/usercopy.c:81 usercopy_warn+0xf5/0x120  
mm/usercopy.c:76
CPU: 1 PID: 4479 Comm: syz-executor115 Not tainted 4.18.0-rc3+ #58
Kernel panic - not syncing: panic_on_warn set ...

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_bad_pte.cold.116+0x1cd/0x22b mm/memory.c:774
  zap_pte_range mm/memory.c:1380 [inline]
  zap_pmd_range mm/memory.c:1437 [inline]
  zap_pud_range mm/memory.c:1466 [inline]
  zap_p4d_range mm/memory.c:1487 [inline]
  unmap_page_range+0x1cb9/0x2220 mm/memory.c:1508
  unmap_single_vma+0x1a0/0x310 mm/memory.c:1553
  unmap_vmas+0x120/0x1f0 mm/memory.c:1583
  exit_mmap+0x2c2/0x5b0 mm/mmap.c:3105
  __mmput kernel/fork.c:970 [inline]
  mmput+0x265/0x620 kernel/fork.c:991
  exit_mm kernel/exit.c:544 [inline]
  do_exit+0xea9/0x2750 kernel/exit.c:852
  do_group_exit+0x177/0x440 kernel/exit.c:968
  get_signal+0x88e/0x1970 kernel/signal.c:2468
  do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
  exit_to_usermode_loop+0x2e0/0x370 arch/x86/entry/common.c:162
  prepare_exit_to_usermode+0x342/0x3b0 arch/x86/entry/common.c:197
  retint_user+0x8/0x18
RIP: 0033:0x4731e0
Code: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <00> 00 00 00 00  
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
RSP: 002b:00007ffd426a9928 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000002e7e RCX: 00000000004731e0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffd426a9930
RBP: 0000000000002e7e R08: 0000000000000001 R09: 0000000000e2a880
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000f7e
R13: 000000000003ab5f R14: 0000000000000000 R15: 0000000000000000
CPU: 0 PID: 24313 Comm: syz-executor115 Not tainted 4.18.0-rc3+ #58
swap_info_get: Bad swap file entry 403fffe200725fc
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

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