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Date:   Fri, 12 Jan 2018 17:58:01 -0800
From:   syzbot <syzbot+e631b5eb810eae08510d@...kaller.appspotmail.com>
To:     ast@...nel.org, daniel@...earbox.net, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: KASAN: slab-out-of-bounds Read in map_lookup_elem

Hello,

syzkaller hit the following crash on  
19d28fbd306e7ae7c1acf05c3e6968b56f0d196b
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e631b5eb810eae08510d@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1515782899.456:8): avc:  denied  { sys_admin } for   
pid=3501 comm="syzkaller937663" capability=21   
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns  
permissive=1
audit: type=1400 audit(1515782899.512:9): avc:  denied  { sys_chroot } for   
pid=3502 comm="syzkaller937663" capability=18   
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns  
permissive=1
==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:344 [inline]
BUG: KASAN: slab-out-of-bounds in map_lookup_elem+0x4dc/0xbd0  
kernel/bpf/syscall.c:584
Read of size 2097153 at addr ffff8801bfc7e690 by task syzkaller937663/3502

CPU: 0 PID: 3502 Comm: syzkaller937663 Not tainted 4.15.0-rc7+ #185
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
  check_memory_region_inline mm/kasan/kasan.c:260 [inline]
  check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
  memcpy+0x23/0x50 mm/kasan/kasan.c:302
  memcpy include/linux/string.h:344 [inline]
  map_lookup_elem+0x4dc/0xbd0 kernel/bpf/syscall.c:584
  SYSC_bpf kernel/bpf/syscall.c:1808 [inline]
  SyS_bpf+0x922/0x4400 kernel/bpf/syscall.c:1782
  entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x440ab9
RSP: 002b:00000000007dff68 EFLAGS: 00000203 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fffc494ea60 RCX: 0000000000440ab9
RDX: 0000000000000018 RSI: 0000000020eab000 RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000203 R12: 0000000000402290
R13: 0000000000402320 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3502:
  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]
  bpf_map_area_alloc+0x32/0x80 kernel/bpf/syscall.c:123
  array_map_alloc+0x351/0xa00 kernel/bpf/arraymap.c:96
  find_and_alloc_map kernel/bpf/syscall.c:105 [inline]
  map_create kernel/bpf/syscall.c:404 [inline]
  SYSC_bpf kernel/bpf/syscall.c:1805 [inline]
  SyS_bpf+0x7f8/0x4400 kernel/bpf/syscall.c:1782
  entry_SYSCALL_64_fastpath+0x23/0x9a

Freed by task 1966:
  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
  seq_release fs/seq_file.c:366 [inline]
  single_release+0x80/0xb0 fs/seq_file.c:602
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
  exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x98/0x9a

The buggy address belongs to the object at ffff8801bfc7e5c0
  which belongs to the cache kmalloc-256 of size 256
The buggy address is located 208 bytes inside of
  256-byte region [ffff8801bfc7e5c0, ffff8801bfc7e6c0)
The buggy address belongs to the page:
page:ffffea0006ff1f80 count:1 mapcount:0 mapping:ffff8801bfc7e0c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bfc7e0c0 0000000000000000 000000010000000c
raw: ffffea00070149e0 ffffea0006ff2be0 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801bfc7e580: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
  ffff8801bfc7e600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801bfc7e680: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
                                            ^
  ffff8801bfc7e700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801bfc7e780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@...glegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
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If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
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