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[195.135.220.15]) by mx.google.com with ESMTPS id f6si4282126edx.449.2019.07.22.00.25.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jul 2019 00:25:11 -0700 (PDT) Received-SPF: pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 5478DAE2D; Mon, 22 Jul 2019 07:25:10 +0000 (UTC) Subject: Re: [v4 PATCH 2/2] mm: mempolicy: handle vma with unmovable pages mapped correctly in mbind To: Yang Shi , mhocko@kernel.org, mgorman@techsingularity.net, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org References: <1563556862-54056-1-git-send-email-yang.shi@linux.alibaba.com> <1563556862-54056-3-git-send-email-yang.shi@linux.alibaba.com> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <1563556862-54056-3-git-send-email-yang.shi@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/19/19 7:21 PM, Yang Shi wrote: > When running syzkaller internally, we ran into the below bug on 4.9.x > kernel: > > kernel BUG at mm/huge_memory.c:2124! > invalid opcode: 0000 [#1] SMP KASAN > Dumping ftrace buffer: > (ftrace buffer empty) > Modules linked in: > CPU: 0 PID: 1518 Comm: syz-executor107 Not tainted 4.9.168+ #2 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.5.1 01/01/2011 > task: ffff880067b34900 task.stack: ffff880068998000 > RIP: 0010:[] [] split_huge_page_to_list+0x8fb/0x1030 mm/huge_memory.c:2124 > RSP: 0018:ffff88006899f980 EFLAGS: 00010286 > RAX: 0000000000000000 RBX: ffffea00018f1700 RCX: 0000000000000000 > RDX: 1ffffd400031e2e7 RSI: 0000000000000001 RDI: ffffea00018f1738 > RBP: ffff88006899f9e8 R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000000 R11: fffffbfff0d8b13e R12: ffffea00018f1400 > R13: ffffea00018f1400 R14: ffffea00018f1720 R15: ffffea00018f1401 > FS: 00007fa333996740(0000) GS:ffff88006c600000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020000040 CR3: 0000000066b9c000 CR4: 00000000000606f0 > Stack: > 0000000000000246 ffff880067b34900 0000000000000000 ffff88007ffdc000 > 0000000000000000 ffff88006899f9e8 ffffffff812b4015 ffff880064c64e18 > ffffea00018f1401 dffffc0000000000 ffffea00018f1700 0000000020ffd000 > Call Trace: > [] split_huge_page include/linux/huge_mm.h:100 [inline] > [] queue_pages_pte_range+0x7e1/0x1480 mm/mempolicy.c:538 > [] walk_pmd_range mm/pagewalk.c:50 [inline] > [] walk_pud_range mm/pagewalk.c:90 [inline] > [] walk_pgd_range mm/pagewalk.c:116 [inline] > [] __walk_page_range+0x44a/0xdb0 mm/pagewalk.c:208 > [] walk_page_range+0x154/0x370 mm/pagewalk.c:285 > [] queue_pages_range+0x115/0x150 mm/mempolicy.c:694 > [] do_mbind mm/mempolicy.c:1241 [inline] > [] SYSC_mbind+0x3c3/0x1030 mm/mempolicy.c:1370 > [] SyS_mbind+0x46/0x60 mm/mempolicy.c:1352 > [] do_syscall_64+0x1d2/0x600 arch/x86/entry/common.c:282 > [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb > Code: c7 80 1c 02 00 e8 26 0a 76 01 <0f> 0b 48 c7 c7 40 46 45 84 e8 4c > RIP [] split_huge_page_to_list+0x8fb/0x1030 mm/huge_memory.c:2124 > RSP > > with the below test: > > ---8<--- > > uint64_t r[1] = {0xffffffffffffffff}; > > int main(void) > { > syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0); > intptr_t res = 0; > res = syscall(__NR_socket, 0x11, 3, 0x300); > if (res != -1) > r[0] = res; > *(uint32_t*)0x20000040 = 0x10000; > *(uint32_t*)0x20000044 = 1; > *(uint32_t*)0x20000048 = 0xc520; > *(uint32_t*)0x2000004c = 1; > syscall(__NR_setsockopt, r[0], 0x107, 0xd, 0x20000040, 0x10); > syscall(__NR_mmap, 0x20fed000, 0x10000, 0, 0x8811, r[0], 0); > *(uint64_t*)0x20000340 = 2; > syscall(__NR_mbind, 0x20ff9000, 0x4000, 0x4002, 0x20000340, > 0x45d4, 3); > return 0; > } > > ---8<--- > > Actually the test does: > > mmap(0x20000000, 16777216, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000 > socket(AF_PACKET, SOCK_RAW, 768) = 3 > setsockopt(3, SOL_PACKET, PACKET_TX_RING, {block_size=65536, block_nr=1, frame_size=50464, frame_nr=1}, 16) = 0 > mmap(0x20fed000, 65536, PROT_NONE, MAP_SHARED|MAP_FIXED|MAP_POPULATE|MAP_DENYWRITE, 3, 0) = 0x20fed000 > mbind(..., MPOL_MF_STRICT|MPOL_MF_MOVE) = 0 > > The setsockopt() would allocate compound pages (16 pages in this test) > for packet tx ring, then the mmap() would call packet_mmap() to map the > pages into the user address space specified by the mmap() call. > > When calling mbind(), it would scan the vma to queue the pages for > migration to the new node. It would split any huge page since 4.9 > doesn't support THP migration, however, the packet tx ring compound > pages are not THP and even not movable. So, the above bug is triggered. > > However, the later kernel is not hit by this issue due to the > commit d44d363f65780f2ac2 ("mm: don't assume anonymous pages have > SwapBacked flag"), which just removes the PageSwapBacked check for a > different reason. > > But, there is a deeper issue. According to the semantic of mbind(), it > should return -EIO if MPOL_MF_MOVE or MPOL_MF_MOVE_ALL was specified and > MPOL_MF_STRICT was also specified, but the kernel was unable to move > all existing pages in the range. The tx ring of the packet socket is > definitely not movable, however, mbind() returns success for this case. > > Although the most socket file associates with non-movable pages, but XDP > may have movable pages from gup. So, it sounds not fine to just check > the underlying file type of vma in vma_migratable(). > > Change migrate_page_add() to check if the page is movable or not, if it > is unmovable, just return -EIO. But do not abort pte walk immediately, > since there may be pages off LRU temporarily. We should migrate other > pages if MPOL_MF_MOVE* is specified. Set has_unmovable flag if some > paged could not be not moved, then return -EIO for mbind() eventually. > > With this change the above test would return -EIO as expected. > > Cc: Vlastimil Babka > Cc: Michal Hocko > Cc: Mel Gorman > Signed-off-by: Yang Shi Reviewed-by: Vlastimil Babka Thanks!