linux-kernel - BUG: unable to handle kernel NULL pointer dereference in do_sys

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Message-ID: <000000000000410ab4056fc0f5ec@google.com>
Date:   Thu, 28 Jun 2018 22:17:02 -0700
From:   syzbot <syzbot+2c7e8f74f8b2571c87e8@...kaller.appspotmail.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: BUG: unable to handle kernel NULL pointer dereference in do_sys_poll

Hello,

syzbot found the following crash on:

HEAD commit:    90368a37fbbe Merge tag 'printk-for-4.18-rc3' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=109168df800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a63be0c83e84d370
dashboard link: https://syzkaller.appspot.com/bug?extid=2c7e8f74f8b2571c87e8
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=11ce8f38400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15967188400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2c7e8f74f8b2571c87e8@...kaller.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)
random: sshd: uninitialized urandom read (32 bytes read)
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 1aec04067 P4D 1aec04067 PUD 1aed28067 PMD 0
Oops: 0010 [#1] SMP KASAN
CPU: 0 PID: 4522 Comm: syz-executor146 Not tainted 4.18.0-rc2+ #121
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff8801c3dbf758 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801aa717a80 RCX: ffffffff85ec9112
RDX: ffff8801c3dbfab0 RSI: ffff8801aa717a80 RDI: ffff8801b13a5040
RBP: ffff8801c3dbf800 R08: ffff8801aec18040 R09: ffffed0035ffd000
R10: ffffed0035ffd000 R11: ffff8801affe8003 R12: ffff8801c3dbfab0
R13: ffff8801b13a5040 R14: ffffffff8818a920 R15: ffff8801ae4c2980
FS:  00000000009a6880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000001af185000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  vfs_poll include/linux/poll.h:86 [inline]
  do_pollfd fs/select.c:825 [inline]
  do_poll fs/select.c:873 [inline]
  do_sys_poll+0x74d/0x1180 fs/select.c:967
  __do_sys_poll fs/select.c:1025 [inline]
  __se_sys_poll fs/select.c:1013 [inline]
  __x64_sys_poll+0x197/0x530 fs/select.c:1013
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43fd09
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 6b 45 00 00 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffea215df98 EFLAGS: 00000213 ORIG_RAX: 0000000000000007
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fd09
RDX: 0000000000000006 RSI: 0000000000000003 RDI: 0000000020003900
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000213 R12: 0000000000401630
R13: 00000000004016c0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
Dumping ftrace buffer:
    (ftrace buffer empty)
CR2: 0000000000000000
---[ end trace 930be81983fe1d48 ]---
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff8801c3dbf758 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801aa717a80 RCX: ffffffff85ec9112
RDX: ffff8801c3dbfab0 RSI: ffff8801aa717a80 RDI: ffff8801b13a5040
RBP: ffff8801c3dbf800 R08: ffff8801aec18040 R09: ffffed0035ffd000
R10: ffffed0035ffd000 R11: ffff8801affe8003 R12: ffff8801c3dbfab0
R13: ffff8801b13a5040 R14: ffffffff8818a920 R15: ffff8801ae4c2980
FS:  00000000009a6880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000001af185000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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