From: Laura Abbott <labbott@redhat.com>
To: Kees Cook <keescook@chromium.org>,
Tommi Rantala <tommi.t.rantala@nokia.com>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Eric Biggers <ebiggers@google.com>,
Dave Jones <davej@codemonkey.org.uk>
Subject: Re: sudo x86info -a => kernel BUG at mm/usercopy.c:78!
Date: Thu, 30 Mar 2017 10:27:47 -0700 [thread overview]
Message-ID: <3890813c-c891-89a5-c16f-66240a794319@redhat.com> (raw)
In-Reply-To: <CAGXu5jKo4gw=RHCmcY3v+GTiUUgteLbmvHDghd-Lrm7RprL8=Q@mail.gmail.com>
On 03/30/2017 09:45 AM, Kees Cook wrote:
> On Wed, Mar 29, 2017 at 11:44 PM, Tommi Rantala
> <tommi.t.rantala@nokia.com> wrote:
>> Hi,
>>
>> Running:
>>
>> $ sudo x86info -a
>>
>> On this HP ZBook 15 G3 laptop kills the x86info process with segfault and
>> produces the following kernel BUG.
>>
>> $ git describe
>> v4.11-rc4-40-gfe82203
>>
>> It is also reproducible with the fedora kernel: 4.9.14-200.fc25.x86_64
>>
>> Full dmesg output here: https://pastebin.com/raw/Kur2mpZq
>>
>> [ 51.418954] usercopy: kernel memory exposure attempt detected from
>> ffff880000090000 (dma-kmalloc-256) (4096 bytes)
>
> This seems like a real exposure: the copy is attempting to read 4096
> bytes from a 256 byte object.
>
>> [...]
>> [ 51.419063] Call Trace:
>> [ 51.419066] read_mem+0x70/0x120
>> [ 51.419069] __vfs_read+0x28/0x130
>> [ 51.419072] ? security_file_permission+0x9b/0xb0
>> [ 51.419075] ? rw_verify_area+0x4e/0xb0
>> [ 51.419077] vfs_read+0x96/0x130
>> [ 51.419079] SyS_read+0x46/0xb0
>> [ 51.419082] ? SyS_lseek+0x87/0xb0
>> [ 51.419085] entry_SYSCALL_64_fastpath+0x1a/0xa9
>
> I can't reproduce this myself, so I assume it's some specific /proc or
> /sys file that I don't have. Are you able to get a strace of x86info
> as it runs to see which file it is attempting to read here?
>
> Thanks!
>
> -Kees
>
I can't see this on any of my Fedora systems. It looks like this
is trying to read /dev/mem so I suspect your BIOS is putting out
unexpected values. If you turn off hardened usercopy does x86info
give you reasonable values? I'd also echo getting an strace.
Thanks,
Laura
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next prev parent reply other threads:[~2017-03-30 17:27 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-30 6:44 Tommi Rantala
2017-03-30 16:45 ` Kees Cook
2017-03-30 17:20 ` Mark Rutland
2017-03-30 17:27 ` Laura Abbott [this message]
2017-03-30 17:37 ` Kees Cook
2017-03-30 17:44 ` Laura Abbott
2017-03-31 5:44 ` Tommi Rantala
2017-03-30 19:41 ` Dave Jones
2017-03-30 19:52 ` Kees Cook
2017-03-30 20:01 ` Dave Jones
2017-03-31 5:40 ` Tommi Rantala
2017-03-31 6:59 ` Tommi Rantala
2017-03-31 17:17 ` Dave Jones
2017-03-31 17:32 ` Kees Cook
2017-03-31 18:03 ` Dave Jones
2017-03-31 18:57 ` Andy Lutomirski
2017-03-31 18:26 ` Linus Torvalds
2017-03-31 19:32 ` Tommi Rantala
2017-04-04 22:37 ` Kees Cook
2017-04-04 22:55 ` Linus Torvalds
2017-04-04 22:59 ` Kees Cook
2017-04-05 0:22 ` Linus Torvalds
2017-04-05 19:39 ` Kees Cook
2017-03-31 23:58 ` Kees Cook
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