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[195.135.221.5]) by mx.google.com with ESMTPS id d65si11459953pfc.201.2018.12.17.07.07.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Dec 2018 07:07:21 -0800 (PST) Received-SPF: pass (google.com: domain of osalvador@suse.de designates 195.135.221.5 as permitted sender) client-ip=195.135.221.5; Authentication-Results: mx.google.com; spf=pass (google.com: domain of osalvador@suse.de designates 195.135.221.5 as permitted sender) smtp.mailfrom=osalvador@suse.de Received: from emea4-mta.ukb.novell.com ([10.120.13.87]) by smtp.nue.novell.com with ESMTP (TLS encrypted); Mon, 17 Dec 2018 16:07:18 +0100 Received: from d104.suse.de (nwb-a10-snat.microfocus.com [10.120.13.202]) by emea4-mta.ukb.novell.com with ESMTP (NOT encrypted); Mon, 17 Dec 2018 15:07:00 +0000 From: Oscar Salvador To: akpm@linux-foundation.org Cc: mhocko@suse.com, vbabka@suse.cz, rppt@linux.vnet.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador Subject: [PATCH] mm, page_alloc: Fix has_unmovable_pages for HugePages Date: Mon, 17 Dec 2018 16:06:51 +0100 Message-Id: <20181217150651.16176-1-osalvador@suse.de> X-Mailer: git-send-email 2.13.7 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: X-Virus-Scanned: ClamAV using ClamSMTP While playing with gigantic hugepages and memory_hotplug, I triggered the following #PF when "cat memoryX/removable": <--- kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 kernel: #PF error: [normal kernel read fault] kernel: PGD 0 P4D 0 kernel: Oops: 0000 [#1] SMP PTI kernel: CPU: 1 PID: 1481 Comm: cat Tainted: G E 4.20.0-rc6-mm1-1-default+ #18 kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 kernel: RIP: 0010:has_unmovable_pages+0x154/0x210 kernel: Code: 1b ff ff ff eb 32 48 8b 45 00 bf 00 10 00 00 a9 00 00 01 00 74 07 0f b6 4d 51 48 d3 e7 e8 c4 81 05 00 48 85 c0 49 89 c1 75 7e <41> 8b 41 08 83 f8 09 74 41 83 f8 1b 74 3c 4d 2b 64 24 58 49 81 ec kernel: RSP: 0018:ffffc90000a1fd30 EFLAGS: 00010246 kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000009 kernel: RDX: ffffffff82aed4f0 RSI: 0000000000001000 RDI: 0000000000001000 kernel: RBP: ffffea0001800000 R08: 0000000000200000 R09: 0000000000000000 kernel: R10: 0000000000001000 R11: 0000000000000003 R12: ffff88813ffd45c0 kernel: R13: 0000000000060000 R14: 0000000000000001 R15: ffffea0000000000 kernel: FS: 00007fd71d9b3500(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 kernel: CR2: 0000000000000008 CR3: 00000001371c2002 CR4: 00000000003606e0 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 kernel: Call Trace: kernel: is_mem_section_removable+0x7d/0x100 kernel: removable_show+0x90/0xb0 kernel: dev_attr_show+0x1c/0x50 kernel: sysfs_kf_seq_show+0xca/0x1b0 kernel: seq_read+0x133/0x380 kernel: __vfs_read+0x26/0x180 kernel: vfs_read+0x89/0x140 kernel: ksys_read+0x42/0x90 kernel: do_syscall_64+0x5b/0x180 kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9 kernel: RIP: 0033:0x7fd71d4c8b41 kernel: Code: fe ff ff 48 8d 3d 27 9e 09 00 48 83 ec 08 e8 96 02 02 00 66 0f 1f 44 00 00 8b 05 ea fc 2c 00 48 63 ff 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 55 53 48 89 d5 48 89 kernel: RSP: 002b:00007ffeab5f6448 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 kernel: RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fd71d4c8b41 kernel: RDX: 0000000000020000 RSI: 00007fd71d809000 RDI: 0000000000000003 kernel: RBP: 0000000000020000 R08: ffffffffffffffff R09: 0000000000000000 kernel: R10: 000000000000038b R11: 0000000000000246 R12: 00007fd71d809000 kernel: R13: 0000000000000003 R14: 00007fd71d80900f R15: 0000000000020000 kernel: Modules linked in: af_packet(E) xt_tcpudp(E) ipt_REJECT(E) xt_conntrack(E) nf_conntrack(E) nf_defrag_ipv4(E) ip_set(E) nfnetlink(E) ebtable_nat(E) ebtable_broute(E) bridge(E) stp(E) llc(E) iptable_mangle(E) iptable_raw(E) iptable_security(E) ebtable_filter(E) ebtables(E) iptable_filter(E) ip_tables(E) x_tables(E) kvm_intel(E) kvm(E) irqbypass(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) bochs_drm(E) ttm(E) drm_kms_helper(E) drm(E) aesni_intel(E) virtio_net(E) syscopyarea(E) net_failover(E) sysfillrect(E) failover(E) aes_x86_64(E) crypto_simd(E) sysimgblt(E) cryptd(E) pcspkr(E) glue_helper(E) parport_pc(E) fb_sys_fops(E) i2c_piix4(E) parport(E) button(E) btrfs(E) libcrc32c(E) xor(E) zstd_decompress(E) zstd_compress(E) raid6_pq(E) sd_mod(E) ata_generic(E) ata_piix(E) ahci(E) libahci(E) serio_raw(E) crc32c_intel(E) virtio_pci(E) virtio_ring(E) virtio(E) libata(E) sg(E) scsi_mod(E) autofs4(E) kernel: CR2: 0000000000000008 kernel: ---[ end trace 49cade81474e40e7 ]--- kernel: RIP: 0010:has_unmovable_pages+0x154/0x210 kernel: Code: 1b ff ff ff eb 32 48 8b 45 00 bf 00 10 00 00 a9 00 00 01 00 74 07 0f b6 4d 51 48 d3 e7 e8 c4 81 05 00 48 85 c0 49 89 c1 75 7e <41> 8b 41 08 83 f8 09 74 41 83 f8 1b 74 3c 4d 2b 64 24 58 49 81 ec kernel: RSP: 0018:ffffc90000a1fd30 EFLAGS: 00010246 kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000009 kernel: RDX: ffffffff82aed4f0 RSI: 0000000000001000 RDI: 0000000000001000 kernel: RBP: ffffea0001800000 R08: 0000000000200000 R09: 0000000000000000 kernel: R10: 0000000000001000 R11: 0000000000000003 R12: ffff88813ffd45c0 kernel: R13: 0000000000060000 R14: 0000000000000001 R15: ffffea0000000000 kernel: FS: 00007fd71d9b3500(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 kernel: CR2: 0000000000000008 CR3: 00000001371c2002 CR4: 00000000003606e0 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---> The reason is we do not pass the Head to page_hstate(), and so, the call to compound_order() in page_hstate() returns 0, so we end up checking all hstates's size to match PAGE_SIZE. Obviously, we do not find any hstate matching that size, and we return NULL. Then, we dereference that NULL pointer in hugepage_migration_supported() and we got the #PF from above. Fix that by getting the head page before calling page_hstate(). Signed-off-by: Oscar Salvador --- mm/page_alloc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a6e7bfd18cde..18d41e85f672 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -8038,11 +8038,12 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, * handle each tail page individually in migration. */ if (PageHuge(page)) { + struct page *head = compound_head(page); - if (!hugepage_migration_supported(page_hstate(page))) + if (!hugepage_migration_supported(page_hstate(head))) goto unmovable; - iter = round_up(iter + 1, 1<