BUG: bad usercopy in __check_object_size (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=1618ac21400000
kernel config: https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf
dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a3c9d2...@syzkaller.appspotmail.com

do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457099
usercopy: Kernel memory overwrite attempt detected to spans multiple pages
(offset 0, size 64)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:102!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 15327 Comm: syz-executor2 Not tainted 4.19.0-rc2+ #50
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:90
Code: c0 e8 8a 23 b2 ff 48 8b 55 c0 49 89 d9 4d 89 f0 ff 75 c8 4c 89 e1 4c
89 ee 48 c7 c7 80 48 15 88 ff 75 d0 41 57 e8 5a 38 98 ff <0f> 0b e8 5f 23
b2 ff e8 8a 6e f5 ff 8b 95 5c fe ff ff 4d 89 e0 31
RSP: 0018:ffff88019c5ced40 EFLAGS: 00010082
RAX: 000000000000005f RBX: ffffffff881545a0 RCX: ffffc9000728f000
RDX: 0000000000000000 RSI: ffffffff8164f825 RDI: 0000000000000005
RBP: ffff88019c5ced98 R08: ffff8801a3dd23c0 R09: ffffed003b5c3ee2
R10: ffffed003b5c3ee2 R11: ffff8801dae1f717 R12: ffffffff88154ac0
R13: ffffffff881546e0 R14: ffffffff881545a0 R15: ffffffff881545a0
FS: 00007ff971688700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2cb25000 CR3: 00000001d38c1000 CR4: 00000000001406f0
DR0: 00000000200001c0 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
check_page_span mm/usercopy.c:212 [inline]
check_heap_object mm/usercopy.c:241 [inline]
__check_object_size.cold.2+0x23/0x134 mm/usercopy.c:266
check_object_size include/linux/thread_info.h:119 [inline]
__copy_from_user_inatomic include/linux/uaccess.h:65 [inline]
__probe_kernel_read+0xda/0x1c0 mm/maccess.c:33
show_opcodes+0x4c/0x70 arch/x86/kernel/dumpstack.c:109
show_ip+0x31/0x36 arch/x86/kernel/dumpstack.c:126
show_iret_regs+0x14/0x38 arch/x86/kernel/dumpstack.c:131
__show_regs+0x1c/0x60 arch/x86/kernel/process_64.c:72
show_regs_if_on_stack.constprop.10+0x36/0x39
arch/x86/kernel/dumpstack.c:149
show_trace_log_lvl+0x25d/0x28c arch/x86/kernel/dumpstack.c:274
show_stack+0x38/0x3a arch/x86/kernel/dumpstack.c:293
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
fail_dump lib/fault-inject.c:51 [inline]
should_fail.cold.4+0xa/0x17 lib/fault-inject.c:149
__should_failslab+0x124/0x180 mm/failslab.c:32
should_failslab+0x9/0x14 mm/slab_common.c:1557
slab_pre_alloc_hook mm/slab.h:423 [inline]
slab_alloc_node mm/slab.c:3299 [inline]
kmem_cache_alloc_node_trace+0x5a/0x740 mm/slab.c:3661
__do_kmalloc_node mm/slab.c:3681 [inline]
__kmalloc_node_track_caller+0x33/0x70 mm/slab.c:3696
__kmalloc_reserve.isra.39+0x41/0xe0 net/core/skbuff.c:137
__alloc_skb+0x155/0x770 net/core/skbuff.c:205
alloc_skb_fclone include/linux/skbuff.h:1037 [inline]
tipc_buf_acquire+0x2d/0xf0 net/tipc/msg.c:66
named_prepare_buf+0x8d/0x4b0 net/tipc/name_distr.c:71
tipc_named_publish+0x433/0xa80 net/tipc/name_distr.c:99
tipc_nametbl_publish+0x702/0xbb0 net/tipc/name_table.c:630
tipc_sk_publish+0x236/0x530 net/tipc/socket.c:2604
tipc_sk_join net/tipc/socket.c:2779 [inline]
tipc_setsockopt+0x613/0xd70 net/tipc/socket.c:2883
__sys_setsockopt+0x1ba/0x3c0 net/socket.c:1900
__do_sys_setsockopt net/socket.c:1911 [inline]
__se_sys_setsockopt net/socket.c:1908 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1908
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457099
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff971687c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007ff9716886d4 RCX: 0000000000457099
RDX: 0000000000000087 RSI: 000000000000010f RDI: 0000000000000006
RBP: 0000000000930140 R08: 000000000000013f R09: 0000000000000000
R10: 0000000020000180 R11: 0000000000000246 R12: 0000000000000005
R13: 00000000004d6570 R14: 00000000004c9ad7 R15: 0000000000000009
Modules linked in:
Dumping ftrace buffer:
(ftrace buffer empty)
---[ end trace d7af0d687a56e2e0 ]---
RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:90
Code: c0 e8 8a 23 b2 ff 48 8b 55 c0 49 89 d9 4d 89 f0 ff 75 c8 4c 89 e1 4c
89 ee 48 c7 c7 80 48 15 88 ff 75 d0 41 57 e8 5a 38 98 ff <0f> 0b e8 5f 23
b2 ff e8 8a 6e f5 ff 8b 95 5c fe ff ff 4d 89 e0 31
RSP: 0018:ffff88019c5ced40 EFLAGS: 00010082
RAX: 000000000000005f RBX: ffffffff881545a0 RCX: ffffc9000728f000
RDX: 0000000000000000 RSI: ffffffff8164f825 RDI: 0000000000000005
RBP: ffff88019c5ced98 R08: ffff8801a3dd23c0 R09: ffffed003b5c3ee2
R10: ffffed003b5c3ee2 R11: ffff8801dae1f717 R12: ffffffff88154ac0
R13: ffffffff881546e0 R14: ffffffff881545a0 R15: ffffffff881545a0
FS: 00007ff971688700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2cb25000 CR3: 00000001d38c1000 CR4: 00000000001406f0
DR0: 00000000200001c0 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.

[Dmitry Vyukov]

On Fri, Sep 7, 2018 at 5:17 PM, syzbot
<syzbot+a3c9d2...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree: bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=1618ac21400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf
> dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a3c9d2...@syzkaller.appspotmail.com

+Kees, looks like false positive?

> --
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> For more options, visit https://groups.google.com/d/optout.

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree: bpf

console output: https://syzkaller.appspot.com/x/log.txt?x=124e64d1400000

kernel config: https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf
dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179f9cd1400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b3e8be400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a3c9d2...@syzkaller.appspotmail.com

entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440479

usercopy: Kernel memory overwrite attempt detected to spans multiple pages
(offset 0, size 64)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:102!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN

CPU: 0 PID: 5340 Comm: syz-executor610 Not tainted 4.19.0-rc2+ #50

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:90
Code: c0 e8 8a 23 b2 ff 48 8b 55 c0 49 89 d9 4d 89 f0 ff 75 c8 4c 89 e1 4c
89 ee 48 c7 c7 80 48 15 88 ff 75 d0 41 57 e8 5a 38 98 ff <0f> 0b e8 5f 23
b2 ff e8 8a 6e f5 ff 8b 95 5c fe ff ff 4d 89 e0 31

RSP: 0018:ffff8801bbcf6d50 EFLAGS: 00010086
RAX: 000000000000005f RBX: ffffffff881545a0 RCX: 0000000000000000

RDX: 0000000000000000 RSI: ffffffff8164f825 RDI: 0000000000000005

RBP: ffff8801bbcf6da8 R08: ffff8801d8f1a500 R09: ffffed003b5c3ee2

R10: ffffed003b5c3ee2 R11: ffff8801dae1f717 R12: ffffffff88154ac0
R13: ffffffff881546e0 R14: ffffffff881545a0 R15: ffffffff881545a0

FS: 000000000225c880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000000455350 CR3: 00000001d90eb000 CR4: 00000000001406f0

Call Trace:
check_page_span mm/usercopy.c:212 [inline]
check_heap_object mm/usercopy.c:241 [inline]
__check_object_size.cold.2+0x23/0x134 mm/usercopy.c:266
check_object_size include/linux/thread_info.h:119 [inline]
__copy_from_user_inatomic include/linux/uaccess.h:65 [inline]
__probe_kernel_read+0xda/0x1c0 mm/maccess.c:33
show_opcodes+0x4c/0x70 arch/x86/kernel/dumpstack.c:109
show_ip+0x31/0x36 arch/x86/kernel/dumpstack.c:126
show_iret_regs+0x14/0x38 arch/x86/kernel/dumpstack.c:131
__show_regs+0x1c/0x60 arch/x86/kernel/process_64.c:72
show_regs_if_on_stack.constprop.10+0x36/0x39
arch/x86/kernel/dumpstack.c:149
show_trace_log_lvl+0x25d/0x28c arch/x86/kernel/dumpstack.c:274
show_stack+0x38/0x3a arch/x86/kernel/dumpstack.c:293
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
fail_dump lib/fault-inject.c:51 [inline]
should_fail.cold.4+0xa/0x17 lib/fault-inject.c:149
__should_failslab+0x124/0x180 mm/failslab.c:32
should_failslab+0x9/0x14 mm/slab_common.c:1557
slab_pre_alloc_hook mm/slab.h:423 [inline]

slab_alloc mm/slab.c:3378 [inline]
kmem_cache_alloc_trace+0x2d7/0x750 mm/slab.c:3618
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:707 [inline]
aa_alloc_file_ctx security/apparmor/include/file.h:60 [inline]
apparmor_file_alloc_security+0x168/0xaa0 security/apparmor/lsm.c:438
security_file_alloc+0x4c/0xa0 security/security.c:884
__alloc_file+0x12a/0x470 fs/file_table.c:105
alloc_empty_file+0x72/0x170 fs/file_table.c:150
dentry_open+0x71/0x1d0 fs/open.c:894
open_related_ns+0x1b0/0x210 fs/nsfs.c:177
__tun_chr_ioctl+0x48d/0x4690 drivers/net/tun.c:2901
tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:3179
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440479
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 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe3cf83628 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000440479
RDX: 0000000000000000 RSI: 000000000000894c RDI: 0000000000000004
RBP: 00000000006cb018 R08: 0000000000000001 R09: 0000000000000034
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000

Modules linked in:
Dumping ftrace buffer:
(ftrace buffer empty)

---[ end trace 125c9e5841391893 ]---

RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:90
Code: c0 e8 8a 23 b2 ff 48 8b 55 c0 49 89 d9 4d 89 f0 ff 75 c8 4c 89 e1 4c
89 ee 48 c7 c7 80 48 15 88 ff 75 d0 41 57 e8 5a 38 98 ff <0f> 0b e8 5f 23
b2 ff e8 8a 6e f5 ff 8b 95 5c fe ff ff 4d 89 e0 31

RSP: 0018:ffff8801bbcf6d50 EFLAGS: 00010086
RAX: 000000000000005f RBX: ffffffff881545a0 RCX: 0000000000000000

RDX: 0000000000000000 RSI: ffffffff8164f825 RDI: 0000000000000005

RBP: ffff8801bbcf6da8 R08: ffff8801d8f1a500 R09: ffffed003b5c3ee2

R10: ffffed003b5c3ee2 R11: ffff8801dae1f717 R12: ffffffff88154ac0
R13: ffffffff881546e0 R14: ffffffff881545a0 R15: ffffffff881545a0

FS: 000000000225c880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000000455350 CR3: 00000001d90eb000 CR4: 00000000001406f0

[Kees Cook]

On Fri, Sep 7, 2018 at 8:19 AM, Dmitry Vyukov <dvy...@google.com> wrote:
> On Fri, Sep 7, 2018 at 5:17 PM, syzbot
> <syzbot+a3c9d2...@syzkaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern..
>> git tree: bpf
>> console output: https://syzkaller.appspot.com/x/log.txt?x=1618ac21400000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf
>> dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b
>> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+a3c9d2...@syzkaller.appspotmail.com
>
> +Kees, looks like false positive?

Basically, yes. CONFIG_HARDENED_USERCOPY_PAGESPAN=y should not be used
-- it's for tracking down these cases (not really for general-purpose
"debugging"), but no one is currently working on solving them.

-Kees

--
Kees Cook
Pixel Security

[Tetsuo Handa]

On 2018/09/08 0:29, syzbot wrote:
> syzbot has found a reproducer for the following crash on:
>
> HEAD commit:    28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree:       bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=124e64d1400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf
> dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=179f9cd1400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11b3e8be400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a3c9d2...@syzkaller.appspotmail.com
>
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x440479
> usercopy: Kernel memory overwrite attempt detected to spans multiple pages (offset 0, size 64)!

Kees, is this because check_page_span() is failing to allow on-stack variable

u8 opcodes[OPCODE_BUFSIZE];

which by chance crossed PAGE_SIZE boundary?

[Kees Cook]

There are a lot of failure conditions for the PAGESPAN check. This
might be one (and one that I'm hoping to solve separately).

[Dmitry Vyukov]

Disabled CONFIG_HARDENED_USERCOPY_PAGESPAN on syzbot:
https://github.com/google/syzkaller/commit/be20da425029ecd45b18e99fa5f09691ba0658ea

#syz invalid