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Date: Wed, 3 Dec 2014 17:27:13 +0400
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Andrey Ryabinin <a.ryabinin@...sung.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"nadia.derbey" <Nadia.Derbey@...l.net>, aquini <aquini@...hat.com>,
davidlohr <davidlohr@...com>, Joe Perches <joe@...ches.com>,
manfred <manfred@...orfullife.com>, avagin <avagin@...nvz.org>,
LKML <linux-kernel@...r.kernel.org>,
Kostya Serebryany <kcc@...gle.com>,
Dmitry Chernenkov <dmitryc@...gle.com>,
Andrey Konovalov <andreyknvl@...gle.com>,
Konstantin Khlebnikov <koct9i@...il.com>,
kasan-dev <kasan-dev@...glegroups.com>,
David Rientjes <rientjes@...gle.com>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Luiz Capitulino <lcapitulino@...hat.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: Out-of-bounds access in __do_proc_doulongvec_minmax
On Wed, Dec 3, 2014 at 3:39 PM, Andrey Ryabinin <a.ryabinin@...sung.com> wrote:
> On 12/03/2014 12:04 PM, Dmitry Vyukov wrote:
>> Hi,
>>
>> I am working on AddressSanitizer, a fast memory error detector for kernel:
>> https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel
>>
>> Here is a bug report that I've got while running trinity:
>>
>> ==================================================================
>> BUG: AddressSanitizer: out of bounds access in
>> __do_proc_doulongvec_minmax+0x8a0/0x9a0 at addr ffffffff83980960
>> Read of size 8 by task trinity-c14/6919
>> Out-of-bounds access to the global variable 'zero'
>> [ffffffff83980960-ffffffff83980964) defined at ipc/ipc_sysctl.c:158
>
> This line seems incorrect. Judging from the backtrace below variable 'zero' is
> defined in kernel/sysctl.c:123
>
>
>>
>> CPU: 1 PID: 6919 Comm: trinity-c14 Not tainted 3.18.0-rc1+ #50
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> 0000000000000001 ffff8800b68cf418 ffffffff82c2d3ae 0000000000000000
>> ffff8800b68cf4c0 ffff8800b68cf4a8 ffffffff813eaa81 ffffffff0000000c
>> ffff88010b003600 ffff8800b68cf479 0000000000000296 0000000000000000
>> Call Trace:
>> [<ffffffff813ead71>] __asan_report_load8_noabort+0x51/0x70
>> mm/kasan/report.c:248
>> [<ffffffff810cc3e0>] __do_proc_doulongvec_minmax+0x8a0/0x9a0
>> kernel/sysctl.c:2284
>> [< inlined >] proc_doulongvec_minmax+0x50/0x80
>> do_proc_doulongvec_minmax kernel/sysctl.c:2322
>> [<ffffffff810cc530>] proc_doulongvec_minmax+0x50/0x80 kernel/sysctl.c:2345
>> [<ffffffff813c9e5a>] hugetlb_sysctl_handler_common+0x12a/0x3c0
>> mm/hugetlb.c:2270
>> [<ffffffff813cb45c>] hugetlb_mempolicy_sysctl_handler+0x1c/0x20
>> mm/hugetlb.c:2293
>> [<ffffffff8153e6e9>] proc_sys_call_handler+0x179/0x1f0
>> fs/proc/proc_sysctl.c:506
>> [<ffffffff8153e76f>] proc_sys_write+0xf/0x20 fs/proc/proc_sysctl.c:524
>> [<ffffffff813f1563>] __kernel_write+0x123/0x440 fs/read_write.c:502
>> [<ffffffff8147ebaa>] write_pipe_buf+0x14a/0x1d0 fs/splice.c:1074
>> [< inlined >] __splice_from_pipe+0x22e/0x6f0
>> splice_from_pipe_feed fs/splice.c:769
>> [<ffffffff8147dbde>] __splice_from_pipe+0x22e/0x6f0 fs/splice.c:886
>> [<ffffffff81483211>] splice_from_pipe+0xc1/0x110 fs/splice.c:921
>> [<ffffffff81483298>] default_file_splice_write+0x18/0x50 fs/splice.c:1086
>> [< inlined >] direct_splice_actor+0x104/0x1c0 do_splice_from
>> fs/splice.c:1128
>> [<ffffffff8147cfc4>] direct_splice_actor+0x104/0x1c0 fs/splice.c:1284
>> [<ffffffff8147e5ba>] splice_direct_to_actor+0x24a/0x6f0 fs/splice.c:1237
>> [<ffffffff81483424>] do_splice_direct+0x154/0x270 fs/splice.c:1327
>> [<ffffffff813f3bfb>] do_sendfile+0x5fb/0x1260 fs/read_write.c:1266
>> [< inlined >] SyS_sendfile64+0xfa/0x100 SYSC_sendfile64
>> fs/read_write.c:1327
>> [<ffffffff813f6bea>] SyS_sendfile64+0xfa/0x100 fs/read_write.c:1313
>> [<ffffffff82c464f9>] ia32_do_call+0x13/0x13 arch/x86/ia32/ia32entry.S:444
>> Memory state around the buggy address:
>> ffffffff83980680: 04 f8 f8 f8 f8 f8 f8 f8 02 f8 f8 f8 f8 f8 f8 f8
>> ffffffff83980700: 00 f8 f8 f8 f8 f8 f8 f8 00 f8 f8 f8 f8 f8 f8 f8
>> ffffffff83980780: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 00 00 00 00
>> ffffffff83980800: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 04 f8 f8 f8
>> ffffffff83980880: f8 f8 f8 f8 04 f8 f8 f8 f8 f8 f8 f8 04 f8 f8 f8
>>> ffffffff83980900: f8 f8 f8 f8 04 f8 f8 f8 f8 f8 f8 f8 04 f8 f8 f8
>> ^
>> ffffffff83980980: f8 f8 f8 f8 00 00 00 00 f8 f8 f8 f8 00 00 00 00
>> ffffffff83980a00: 02 f8 f8 f8 f8 f8 f8 f8 00 00 00 00 00 00 00 00
>> ffffffff83980a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ffffffff83980b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ffffffff83980b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ==================================================================
>>
>> The core creates ctl_table as:
>>
>> static int zero;
>> static int one = 1;
>> static int int_max = INT_MAX;
>> static struct ctl_table ipc_kern_table[] = {
>> {
>> ...
>> {
>> .procname = "shm_rmid_forced",
>> .data = &init_ipc_ns.shm_rmid_forced,
>> .maxlen = sizeof(init_ipc_ns.shm_rmid_forced),
>> .mode = 0644,
>> .proc_handler = proc_ipc_dointvec_minmax_orphans,
>> .extra1 = &zero,
>> .extra2 = &one,
>> },
>>
>> But later extra1/2 are casted to *unsigned long**:
>>
>> static int __do_proc_doulongvec_minmax(void *data, struct ctl_table
>> *table, int write, ...
>> {
>> ...
>> min = (unsigned long *) table->extra1;
>> max = (unsigned long *) table->extra2;
>>
>> This leads to bogus bounds check for the sysctl value.
>>
>> The bug is added in commit:
>>
>> commit 9eefe520c814f6f62c5d36a2ddcd3fb99dfdb30e
>> Author: Nadia Derbey <Nadia.Derbey@...l.net>
>> Date: Fri Jul 25 01:48:08 2008 -0700
>>
>> Later zero and one were used in a bunch of other ctl_table's.
>>
>
> I think you are blaming wrong commit. This bug was introduced by
> ed4d4902ebdd7ca8b5a51daaf6bebf4b172895cc ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity")
>
> We have two options to fix this. Reintroduce back hugetlb_zero or make 'zero' unsigned long instead.
> I would prefer the latter, changing type to 'unsigned long' shouldn't harm any other users of this variable.
>
ipc/ipc_sysctl.c also contains zero, one and int_max variables that
are used in a similar way:
static int zero;
static int one = 1;
static int int_max = INT_MAX;
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