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

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

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    0512e0134582 Merge tag 'xfs-4.17-fixes-3' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17eb2d7b800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=968b0b23c7854c0b
dashboard link: https://syzkaller.appspot.com/bug?extid=efae31b384d5badbd620
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=162c6def800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14fe3db7800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+efae31b384d5badbd620@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KASAN: slab-out-of-bounds in ____bpf_csum_update  
net/core/filter.c:1679 [inline]
BUG: KASAN: slab-out-of-bounds in bpf_csum_update+0xb4/0xc0  
net/core/filter.c:1673
Read of size 1 at addr ffff8801d9235b50 by task syz-executor507/4513

CPU: 0 PID: 4513 Comm: syz-executor507 Not tainted 4.17.0-rc7+ #78
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+0x1b9/0x294 lib/dump_stack.c:113
  print_address_description+0x6c/0x20b mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
  ____bpf_csum_update net/core/filter.c:1679 [inline]
  bpf_csum_update+0xb4/0xc0 net/core/filter.c:1673

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801d9235a40
  which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 40 bytes to the right of
  232-byte region [ffff8801d9235a40, ffff8801d9235b28)
The buggy address belongs to the page:
page:ffffea0007648d40 count:1 mapcount:0 mapping:ffff8801d9235040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d9235040 0000000000000000 000000010000000c
raw: ffffea00074360a0 ffff8801d944d848 ffff8801d9bdd6c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d9235a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d9235a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d9235b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                  ^
  ffff8801d9235b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d9235c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: KASAN: slab-out-of-bounds Read in bpf_csum_update

[Dmitry Vyukov]

On Mon, Jun 4, 2018 at 1:36 AM, syzbot
<syzbot+efae31b384d5badbd620@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    0512e0134582 Merge tag 'xfs-4.17-fixes-3' of git://git.ker..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17eb2d7b800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=968b0b23c7854c0b
> dashboard link: https://syzkaller.appspot.com/bug?extid=efae31b384d5badbd620
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=162c6def800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14fe3db7800000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+efae31b384d5badbd620@syzkaller.appspotmail.com
>
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in ____bpf_csum_update net/core/filter.c:1679
> [inline]
> BUG: KASAN: slab-out-of-bounds in bpf_csum_update+0xb4/0xc0
> net/core/filter.c:1673
> Read of size 1 at addr ffff8801d9235b50 by task syz-executor507/4513
>
> CPU: 0 PID: 4513 Comm: syz-executor507 Not tainted 4.17.0-rc7+ #78
> 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+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
>  ____bpf_csum_update net/core/filter.c:1679 [inline]
>  bpf_csum_update+0xb4/0xc0 net/core/filter.c:1673

/\/\/\/\/\

Are there any known bugs with unwind through bpf functions?

> Allocated by task 0:
> (stack is not available)
>
> Freed by task 0:
> (stack is not available)
>
> The buggy address belongs to the object at ffff8801d9235a40
>  which belongs to the cache skbuff_head_cache of size 232
> The buggy address is located 40 bytes to the right of
>  232-byte region [ffff8801d9235a40, ffff8801d9235b28)
> The buggy address belongs to the page:
> page:ffffea0007648d40 count:1 mapcount:0 mapping:ffff8801d9235040 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801d9235040 0000000000000000 000000010000000c
> raw: ffffea00074360a0 ffff8801d944d848 ffff8801d9bdd6c0 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801d9235a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801d9235a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>
>> ffff8801d9235b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>
>                                                  ^
>  ffff8801d9235b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801d9235c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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Re: KASAN: slab-out-of-bounds Read in bpf_csum_update

[Daniel Borkmann]

On 06/04/2018 07:36 AM, Dmitry Vyukov wrote:
> On Mon, Jun 4, 2018 at 1:36 AM, syzbot
> <syzbot+efae31b384d5badbd620@syzkaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    0512e0134582 Merge tag 'xfs-4.17-fixes-3' of git://git.ker..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=17eb2d7b800000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=968b0b23c7854c0b
>> dashboard link: https://syzkaller.appspot.com/bug?extid=efae31b384d5badbd620
>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=162c6def800000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14fe3db7800000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+efae31b384d5badbd620@syzkaller.appspotmail.com
>>
>> random: sshd: uninitialized urandom read (32 bytes read)
>> random: sshd: uninitialized urandom read (32 bytes read)
>> random: sshd: uninitialized urandom read (32 bytes read)
>> random: sshd: uninitialized urandom read (32 bytes read)
>> ==================================================================
>> BUG: KASAN: slab-out-of-bounds in ____bpf_csum_update net/core/filter.c:1679
>> [inline]
>> BUG: KASAN: slab-out-of-bounds in bpf_csum_update+0xb4/0xc0
>> net/core/filter.c:1673
>> Read of size 1 at addr ffff8801d9235b50 by task syz-executor507/4513
>>
>> CPU: 0 PID: 4513 Comm: syz-executor507 Not tainted 4.17.0-rc7+ #78
>> 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+0x1b9/0x294 lib/dump_stack.c:113
>>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>>  kasan_report_error mm/kasan/report.c:354 [inline]
>>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>>  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
>>  ____bpf_csum_update net/core/filter.c:1679 [inline]
>>  bpf_csum_update+0xb4/0xc0 net/core/filter.c:1673
> 
> /\/\/\/\/\
> 
> Are there any known bugs with unwind through bpf functions?

Looks like you don't have kallsyms export enabled, here's a syzkaller diff
to get jit images exposed, then it should work:

diff --git a/tools/create-image.sh b/tools/create-image.sh
index 9f82482..395a2a0 100755
--- a/tools/create-image.sh
+++ b/tools/create-image.sh
@@ -23,6 +23,7 @@ echo 'SELINUX=disabled' | sudo tee $DIR/etc/selinux/config
 echo "kernel.printk = 7 4 1 3" | sudo tee -a $DIR/etc/sysctl.conf
 echo 'debug.exception-trace = 0' | sudo tee -a $DIR/etc/sysctl.conf
 echo "net.core.bpf_jit_enable = 1" | sudo tee -a $DIR/etc/sysctl.conf
+echo "net.core.bpf_jit_kallsyms = 1" | sudo tee -a $DIR/etc/sysctl.conf
 echo "kernel.softlockup_all_cpu_backtrace = 1" | sudo tee -a $DIR/etc/sysctl.conf
 echo "kernel.kptr_restrict = 0" | sudo tee -a $DIR/etc/sysctl.conf
 echo "kernel.watchdog_thresh = 60" | sudo tee -a $DIR/etc/sysctl.conf

Cheers,
Daniel

Re: KASAN: slab-out-of-bounds Read in bpf_csum_update

[Daniel Borkmann]

On 06/04/2018 01:36 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    0512e0134582 Merge tag 'xfs-4.17-fixes-3' of git://git.ker..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17eb2d7b800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=968b0b23c7854c0b
> dashboard link: https://syzkaller.appspot.com/bug?extid=efae31b384d5badbd620
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=162c6def800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14fe3db7800000

#syz fix: bpf: reject passing modified ctx to helper functions