From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>,
Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
mm-commits@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-next@vger.kernel.org, sfr@canb.auug.org.au,
broonie@kernel.org
Subject: Re: ppc elf_map breakage with MAP_FIXED_NOREPLACE
Date: Thu, 1 Feb 2018 08:43:34 +0530 [thread overview]
Message-ID: <bfecda5e-ae8b-df91-0add-df6322b42a70@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180131131937.GA6740@dhcp22.suse.cz>
On 01/31/2018 06:49 PM, Michal Hocko wrote:
> On Wed 31-01-18 10:35:38, Anshuman Khandual wrote:
>> On 01/30/2018 03:12 PM, Michal Hocko wrote:
> [...]
>>> Anshuman, could you try to run
>>> sed 's@^@@' /proc/self/smaps
>>> on a system with MAP_FIXED_NOREPLACE reverted?
>>>
>> After reverting the following commits from mmotm-2018-01-25-16-20 tag.
>>
>> 67caea694ba5965a52a61fdad495d847f03c4025 ("mm-introduce-map_fixed_safe-fix")
>> 64da2e0c134ecf3936a4c36b949bcf2cdc98977e ("fs-elf-drop-map_fixed-usage-from-elf_map-fix-fix")
>> 645983ab6ca7fd644f52b4c55462b91940012595 ("mm: don't use the same value for MAP_FIXED_NOREPLACE and MAP_SYNC")
>> d77bab291ac435aab91fa214b85efa74a26c9c22 ("fs-elf-drop-map_fixed-usage-from-elf_map-checkpatch-fixes")
>> a75c5f92d9ecb21d3299cc7db48e401cbf335c34 ("fs, elf: drop MAP_FIXED usage from elf_map")
>> 00906d029ffe515221e3939b222c237026af2903 ("mm: introduce MAP_FIXED_NOREPLACE")
>>
>> $sed 's@^@@' /proc/self/smaps
> Interesting
>
>> -------------------------------------------
>> 10000000-10020000 r-xp 00000000 fd:00 10558 /usr/bin/sed
>> 10020000-10030000 r--p 00010000 fd:00 10558 /usr/bin/sed
>> 10030000-10040000 rw-p 00020000 fd:00 10558 /usr/bin/sed
>> 2cbb0000-2cbe0000 rw-p 00000000 00:00 0 [heap]
> We still have a brk and at a different offset. Could you confirm that we
> still try to map previous brk at the clashing address 0x10030000?
yes.
[ 9.295990] vma c000001fc8137c80 start 0000000010030000 end 0000000010040000
next c000001fc81378c0 prev c000001fc8137680 mm c000001fc8108200
prot 8000000000000104 anon_vma (null) vm_ops (null)
pgoff 1003 file (null) private_data (null)
flags: 0x100073(read|write|mayread|maywrite|mayexec|account)
[ 9.296351] CPU: 47 PID: 7537 Comm: sed Not tainted 4.14.0-00006-g4bd92fe-dirty #162
[ 9.296450] Call Trace:
[ 9.296482] [c000001fc70db9b0] [c000000000b180e0] dump_stack+0xb0/0xf0 (unreliable)
[ 9.296588] [c000001fc70db9f0] [c0000000002db0b8] do_brk_flags+0x2d8/0x440
[ 9.296674] [c000001fc70dbac0] [c0000000002db4d0] vm_brk_flags+0x80/0x130
[ 9.296751] [c000001fc70dbb20] [c0000000003d2998] set_brk+0x80/0xe8
[ 9.296824] [c000001fc70dbb60] [c0000000003d2518] load_elf_binary+0x12f8/0x1580
[ 9.296910] [c000001fc70dbc80] [c00000000035d9e0] search_binary_handler+0xd0/0x270
[ 9.296999] [c000001fc70dbd10] [c00000000035f938] do_execveat_common.isra.31+0x658/0x890
[ 9.297089] [c000001fc70dbdf0] [c00000000035ff80] SyS_execve+0x40/0x50
[ 9.297162] [c000001fc70dbe30] [c00000000000b220] system_call+0x58/0x6c
But coming back to when it failed with MAP_FIXED_NOREPLACE, looking into ELF
section details (readelf -aW /usr/bin/sed), there was a PT_LOAD segment with
p_memsz > p_filesz which might be causing set_brk() to be called.
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
...
LOAD 0x020328 0x0000000010030328 0x0000000010030328 0x000384 0x0094a0 RW 0x10000
which can be confirmed by just dumping elf_brk/elf_bss for this particular
instance. (elf_brk > elf_bss)
$dmesg | grep elf_brk
[ 9.571192] elf_brk 10030328 elf_bss 10030000
static int load_elf_binary(struct linux_binprm *bprm)
---------------------
if (unlikely (elf_brk > elf_bss)) {
unsigned long nbyte;
/* There was a PT_LOAD segment with p_memsz > p_filesz
before this one. Map anonymous pages, if needed,
and clear the area. */
retval = set_brk(elf_bss + load_bias,
elf_brk + load_bias,
bss_prot);
---------------------
So is not there a chance that subsequent file mapping might be overlapping
with these anon mappings ? I mean may be thats how ELF loading might be
happening right now.
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next prev parent reply other threads:[~2018-02-01 3:13 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-05 0:20 mmotm 2018-01-04-16-19 uploaded akpm
2018-01-05 6:43 ` Anshuman Khandual
2018-01-05 8:46 ` Michal Hocko
2018-01-07 6:49 ` Anshuman Khandual
2018-01-07 9:02 ` ppc elf_map breakage with MAP_FIXED_NOREPLACE (was: Re: mmotm 2018-01-04-16-19 uploaded) Michal Hocko
2018-01-07 11:26 ` Michael Ellerman
2018-01-08 3:02 ` ppc elf_map breakage with MAP_FIXED_NOREPLACE Anshuman Khandual
2018-01-08 22:12 ` Michael Ellerman
2018-01-09 11:48 ` Anshuman Khandual
2018-01-09 16:13 ` Michal Hocko
2018-01-11 10:08 ` Anshuman Khandual
2018-01-17 8:07 ` Michal Hocko
2018-01-23 11:25 ` Anshuman Khandual
2018-01-23 12:45 ` Michal Hocko
2018-01-23 15:58 ` Anshuman Khandual
2018-01-23 16:06 ` Michal Hocko
2018-01-24 5:09 ` Anshuman Khandual
2018-01-24 9:05 ` Michal Hocko
2018-01-26 12:34 ` Anshuman Khandual
2018-01-26 14:04 ` Michal Hocko
2018-01-29 2:47 ` Anshuman Khandual
2018-01-29 5:32 ` Anshuman Khandual
2018-01-29 13:22 ` Michal Hocko
2018-01-30 3:35 ` Michael Ellerman
2018-01-30 9:42 ` Michal Hocko
2018-01-31 5:05 ` Anshuman Khandual
2018-01-31 13:19 ` Michal Hocko
2018-02-01 3:13 ` Anshuman Khandual [this message]
2018-02-01 13:10 ` Michal Hocko
2018-02-01 13:40 ` Michal Hocko
2018-02-01 20:55 ` Kees Cook
2018-02-13 10:04 ` [RFC PATCH] elf: enforce MAP_FIXED on overlaying elf segments (was: Re: ppc elf_map breakage with MAP_FIXED_NOREPLACE) Michal Hocko
2018-02-14 16:30 ` Khalid Aziz
2018-02-01 13:48 ` ppc elf_map breakage with MAP_FIXED_NOREPLACE Michal Hocko
2018-02-01 21:06 ` Kees Cook
2018-02-12 14:48 ` Michal Hocko
2018-02-13 1:02 ` Anshuman Khandual
2018-02-13 6:49 ` Anshuman Khandual
2018-02-13 10:00 ` Michal Hocko
2018-01-05 12:14 ` mmotm 2018-01-04-16-19 uploaded Michal Hocko
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