Subject: WARNING: kmalloc bug in memdup_user (3)

From: syzbot <[email-masked]>
Date: Wed, 16 May 2018 08:35:02 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    c5c7d7f3c451 Merge branch 'bpf-sock-hashmap'
git tree:       bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1626ae37800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=10c4dc62055b68f5
dashboard link: https://syzkaller.appspot.com/bug?extid=0f92a17b0706231d0a09
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=126a5197800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1598c477800000

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)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
WARNING: CPU: 0 PID: 4531 at mm/slab_common.c:996 kmalloc_slab+0x56/0x70  
mm/slab_common.c:996
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4531 Comm: syz-executor594 Not tainted 4.17.0-rc3+ #9
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
  panic+0x22f/0x4de kernel/panic.c:184
  __warn.cold.8+0x163/0x1b3 kernel/panic.c:536
  report_bug+0x252/0x2d0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:178 [inline]
  do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296
  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:kmalloc_slab+0x56/0x70 mm/slab_common.c:996
RSP: 0018:ffff8801ad4b7c48 EFLAGS: 00010246
RAX: 0000000000000000 RBX: fffffffffffffff4 RCX: ffffffff8185e678
RDX: ffffffff8185e6eb RSI: 0000000000000000 RDI: 00000000fffffffd
RBP: ffff8801ad4b7c48 R08: ffff8801adb3e2c0 R09: ffffed0035ba1f08
R10: ffffed0035ba1f08 R11: ffff8801add0f843 R12: 00000000fffffffd
R13: 0000000020000240 R14: 00000000ffffffff R15: 00000000014200c0
  __do_kmalloc mm/slab.c:3713 [inline]
  __kmalloc_track_caller+0x21/0x760 mm/slab.c:3733
  memdup_user+0x2c/0xa0 mm/util.c:160
  map_delete_elem+0x21b/0x4e0 kernel/bpf/syscall.c:796
  __do_sys_bpf kernel/bpf/syscall.c:2128 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:2096 [inline]
  __x64_sys_bpf+0x33f/0x4f0 kernel/bpf/syscall.c:2096
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43fd89
RSP: 002b:00007ffe3ad9ad78 EFLAGS: 00000213 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fd89
RDX: 0000000000000010 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000213 R12: 00000000004016b0
R13: 0000000000401740 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

---
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 [email-masked].

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