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Violators will be prosecuted for from ; Thu, 1 Feb 2018 03:13:42 -0000 Subject: Re: ppc elf_map breakage with MAP_FIXED_NOREPLACE References: <2a05eaf2-20fd-57a8-d4bd-5a1fbf57686c@linux.vnet.ibm.com> <20180124090539.GH1526@dhcp22.suse.cz> <5acba3c2-754d-e449-24ff-a72a0ad0d895@linux.vnet.ibm.com> <20180126140415.GD5027@dhcp22.suse.cz> <15da8c87-e6db-13aa-01c8-a913656bfdb6@linux.vnet.ibm.com> <6db9b33d-fd46-c529-b357-3397926f0733@linux.vnet.ibm.com> <20180129132235.GE21609@dhcp22.suse.cz> <87k1w081e7.fsf@concordia.ellerman.id.au> <20180130094205.GS21609@dhcp22.suse.cz> <5eccdc1b-6a10-b48a-c63f-295f69473d97@linux.vnet.ibm.com> <20180131131937.GA6740@dhcp22.suse.cz> From: Anshuman Khandual Date: Thu, 1 Feb 2018 08:43:34 +0530 MIME-Version: 1.0 In-Reply-To: <20180131131937.GA6740@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Message-Id: Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Anshuman Khandual Cc: Michael Ellerman , "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 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . 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