linux-kernel - KASAN: global-out-of-bounds Read in show

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Date:   Fri, 01 Dec 2017 18:03:01 -0800
From:   syzbot 
        <bot+dc3224b9c8f85af3ad550f98c1bc002062185ea6@...kaller.appspotmail.com>
To:     adobriyan@...il.com, akinobu.mita@...il.com,
        akpm@...ux-foundation.org, bfields@...hat.com, davem@...emloft.net,
        dvyukov@...gle.com, ebiederm@...ssion.com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        mingo@...nel.org, schwidefsky@...ibm.com, sfr@...b.auug.org.au,
        syzkaller-bugs@...glegroups.com, vegard.nossum@...cle.com
Subject: KASAN: global-out-of-bounds Read in show_timer

syzkaller has found reproducer for the following crash on  
fb20eb9d798d2f4c1a75b7fe981d72dfa8d7270d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-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


==================================================================
BUG: KASAN: global-out-of-bounds in show_timer+0x278/0x2b0  
fs/proc/base.c:2303
Read of size 8 at addr ffffffff85343578 by task syzkaller289632/3091

CPU: 1 PID: 3091 Comm: syzkaller289632 Not tainted  
4.15.0-rc1-next-20171201+ #57
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+0x178/0x250 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
  show_timer+0x278/0x2b0 fs/proc/base.c:2303
  seq_read+0x385/0x13d0 fs/seq_file.c:234
  do_loop_readv_writev fs/read_write.c:673 [inline]
  do_iter_read+0x3db/0x5b0 fs/read_write.c:897
  vfs_readv+0x121/0x1c0 fs/read_write.c:959
  do_preadv+0x11b/0x1a0 fs/read_write.c:1043
  SYSC_preadv fs/read_write.c:1093 [inline]
  SyS_preadv+0x30/0x40 fs/read_write.c:1088
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x440209
RSP: 002b:00007fff70ef6758 EFLAGS: 00000217 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007fff70ef6760 RCX: 0000000000440209
RDX: 0000000000000008 RSI: 0000000020508000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 65732f636f72702f R09: 65732f636f72702f
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401ad0
R13: 0000000000401b60 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the variable:
  nstr.44312+0x18/0x40

Memory state around the buggy address:
  ffffffff85343400: fa fa fa fa 00 00 00 fa fa fa fa fa 00 06 fa fa
  ffffffff85343480: fa fa fa fa 07 fa fa fa fa fa fa fa 05 fa fa fa
> ffffffff85343500: fa fa fa fa 07 fa fa fa fa fa fa fa 00 00 00 fa
                                                                 ^
  ffffffff85343580: fa fa fa fa 00 fa fa fa fa fa fa fa 07 fa fa fa
  ffffffff85343600: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3091 Comm: syzkaller289632 Tainted: G    B             
4.15.0-rc1-next-20171201+ #57
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
  panic+0x1e4/0x41c kernel/panic.c:183
  kasan_end_report+0x50/0x50 mm/kasan/report.c:176
  kasan_report_error mm/kasan/report.c:356 [inline]
  kasan_report+0x144/0x340 mm/kasan/report.c:409
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
  show_timer+0x278/0x2b0 fs/proc/base.c:2303
  seq_read+0x385/0x13d0 fs/seq_file.c:234
  do_loop_readv_writev fs/read_write.c:673 [inline]
  do_iter_read+0x3db/0x5b0 fs/read_write.c:897
  vfs_readv+0x121/0x1c0 fs/read_write.c:959
  do_preadv+0x11b/0x1a0 fs/read_write.c:1043
  SYSC_preadv fs/read_write.c:1093 [inline]
  SyS_preadv+0x30/0x40 fs/read_write.c:1088
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x440209
RSP: 002b:00007fff70ef6758 EFLAGS: 00000217 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007fff70ef6760 RCX: 0000000000440209
RDX: 0000000000000008 RSI: 0000000020508000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 65732f636f72702f R09: 65732f636f72702f
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401ad0
R13: 0000000000401b60 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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