From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrey Ryabinin <a.ryabinin@samsung.com>,
Sasha Levin <sasha.levin@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andi Kleen <ak@linux.intel.com>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>, Ning Qu <quning@gmail.com>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Dave Jones <davej@redhat.com>,
stable@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
Konstantin Khlebnikov <koct9i@gmail.com>,
Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH] mm: don't allow fault_around_bytes to be 0
Date: Mon, 28 Jul 2014 12:36:11 +0300 [thread overview]
Message-ID: <20140728093611.GA3975@node.dhcp.inet.fi> (raw)
In-Reply-To: <1406533400-6361-1-git-send-email-a.ryabinin@samsung.com>
On Mon, Jul 28, 2014 at 11:43:20AM +0400, Andrey Ryabinin wrote:
> Sasha Levin triggered use-after-free when fuzzing using trinity and the KASAN
> patchset:
>
> AddressSanitizer: use after free in do_read_fault.isra.40+0x3c2/0x510 at addr ffff88048a733110
> page:ffffea001229ccc0 count:0 mapcount:0 mapping: (null) index:0x0
> page flags: 0xafffff80008000(tail)
> page dumped because: kasan error
> CPU: 6 PID: 9262 Comm: trinity-c104 Not tainted 3.16.0-rc6-next-20140723-sasha-00047-g289342b-dirty #929
> 00000000000000fb 0000000000000000 ffffea001229ccc0 ffff88038ac0fb78
> ffffffffa5e40903 ffff88038ac0fc48 ffff88038ac0fc38 ffffffffa142acfc
> 0000000000000001 ffff880509ff5aa8 ffff88038ac10038 ffff88038ac0fbb0
> Call Trace:
> dump_stack (lib/dump_stack.c:52)
> kasan_report_error (mm/kasan/report.c:98 mm/kasan/report.c:166)
> ? debug_smp_processor_id (lib/smp_processor_id.c:57)
> ? preempt_count_sub (kernel/sched/core.c:2606)
> ? put_lock_stats.isra.13 (./arch/x86/include/asm/preempt.h:98 kernel/locking/lockdep.c:254)
> ? do_read_fault.isra.40 (mm/memory.c:2784 mm/memory.c:2849 mm/memory.c:2898)
> __asan_load8 (mm/kasan/kasan.c:364)
> ? do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
> do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
> ? _raw_spin_unlock (./arch/x86/include/asm/preempt.h:98 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:183)
> ? __pte_alloc (mm/memory.c:598)
> handle_mm_fault (mm/memory.c:3092 mm/memory.c:3225 mm/memory.c:3345 mm/memory.c:3374)
> ? pud_huge (./arch/x86/include/asm/paravirt.h:611 arch/x86/mm/hugetlbpage.c:76)
> __get_user_pages (mm/gup.c:286 mm/gup.c:478)
> __mlock_vma_pages_range (mm/mlock.c:262)
> __mm_populate (mm/mlock.c:710)
> SyS_remap_file_pages (mm/mmap.c:2653 mm/mmap.c:2593)
> tracesys (arch/x86/kernel/entry_64.S:541)
> Read of size 8 by thread T9262:
> Memory state around the buggy address:
> ffff88048a732e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a732f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a732f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a733000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a733080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff88048a733100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff88048a733180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a733200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a733280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a733300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88048a733380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>
> It looks like that pte pointer is invalid in do_fault_around().
> This could happen if fault_around_bytes is set to 0.
> fault_around_pages() and fault_around_mask() calls rounddown_pow_of_to(fault_around_bytes)
> The result of rounddown_pow_of_to is undefined if parameter == 0
> (in my environment it returns 0x8000000000000000).
Ouch. Good catch!
Although, I'm not convinced that it caused the issue. Sasha, did you touch the
debugfs handle?
> One way to fix this would be to return 0 from fault_around_pages() if fault_around_bytes == 0,
> however this would add extra code on fault path.
>
> So let's just forbid to set fault_around_bytes to zero.
> Fault around is not used if fault_around_pages() <= 1, so if anyone doesn't want to use
> it, fault_around_bytes could be set to any value in range [1, 2*PAGE_SIZE - 1]
> instead of 0.
>From user point of view, 0 is perfectly fine. What about untested patch
below?
Other option: get rid of debugfs interface, so fault_around_pages() and
fault_around_mask() will always be known compile time.
There's other problem with the debugfs handle: we don't have serialization
between fault_around_bytes_set() and do_fault_around(). It can end up
badly if fault_around_bytes will be changed under do_fault_around()...
I don't think it worth adding the serialization to hot path to protect
against debug interface.
Any thoughts?
next prev parent reply other threads:[~2014-07-28 9:36 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 19:53 [PATCHv3 0/2] mm: map few pages around fault address if they are in page cache Kirill A. Shutemov
2014-02-27 19:53 ` [PATCHv3 1/2] mm: introduce vm_ops->map_pages() Kirill A. Shutemov
2014-02-27 21:59 ` Dave Hansen
2014-02-27 22:06 ` Linus Torvalds
2014-02-27 22:34 ` Dave Hansen
2014-02-28 0:18 ` Kirill A. Shutemov
2014-02-28 11:50 ` Benjamin Herrenschmidt
2014-02-27 22:08 ` Andrew Morton
2014-03-03 23:16 ` Andrew Morton
2014-03-04 1:26 ` Kirill A. Shutemov
2014-03-05 0:04 ` Rusty Russell
2014-03-05 20:02 ` Andrew Morton
2014-07-24 3:33 ` Sasha Levin
2014-07-24 6:53 ` Andrey Ryabinin
2014-07-24 12:48 ` Sasha Levin
2014-07-24 13:05 ` Sasha Levin
2014-07-24 13:30 ` Konstantin Khlebnikov
2014-07-28 7:43 ` [PATCH] mm: don't allow fault_around_bytes to be 0 Andrey Ryabinin
2014-07-28 7:47 ` Andrey Ryabinin
2014-07-28 9:36 ` Kirill A. Shutemov [this message]
2014-07-28 10:27 ` Andrey Ryabinin
2014-07-28 10:52 ` Kirill A. Shutemov
2014-07-28 12:32 ` Sasha Levin
2014-07-28 22:43 ` David Rientjes
2014-07-28 15:26 ` Dave Hansen
2014-02-27 19:53 ` [PATCHv3 2/2] mm: implement ->map_pages for page cache Kirill A. Shutemov
2014-02-27 21:47 ` Andrew Morton
2014-02-28 0:31 ` Kirill A. Shutemov
2014-04-02 18:03 ` Konstantin Khlebnikov
2014-04-02 19:07 ` Kirill A. Shutemov
2014-02-27 21:28 ` [PATCHv3 0/2] mm: map few pages around fault address if they are in " Linus Torvalds
2014-02-28 0:10 ` Kirill A. Shutemov
2014-02-28 3:52 ` Wilcox, Matthew R
2014-02-28 23:08 ` Linus Torvalds
2014-03-12 14:22 ` Kirill A. Shutemov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140728093611.GA3975@node.dhcp.inet.fi \
--to=kirill@shutemov.name \
--cc=a.ryabinin@samsung.com \
--cc=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=dave.hansen@linux.intel.com \
--cc=davej@redhat.com \
--cc=david@fromorbit.com \
--cc=hughd@google.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=koct9i@gmail.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=matthew.r.wilcox@intel.com \
--cc=mgorman@suse.de \
--cc=quning@gmail.com \
--cc=riel@redhat.com \
--cc=sasha.levin@oracle.com \
--cc=stable@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox