From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 7CB1C6B0665 for ; Fri, 4 Aug 2017 02:47:03 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id k82so754350oih.1 for ; Thu, 03 Aug 2017 23:47:03 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id m78si666736oig.439.2017.08.03.23.47.00 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 03 Aug 2017 23:47:01 -0700 (PDT) Message-Id: <201708040646.v746kkhC024636@www262.sakura.ne.jp> Subject: Re: [PATCH] mm, oom: fix potential data corruption when =?ISO-2022-JP?B?b29tX3JlYXBlciByYWNlcyB3aXRoIHdyaXRlcg==?= From: Tetsuo Handa MIME-Version: 1.0 Date: Fri, 04 Aug 2017 15:46:46 +0900 References: <20170803135902.31977-1-mhocko@kernel.org> In-Reply-To: <20170803135902.31977-1-mhocko@kernel.org> Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, Andrew Morton , Wenwei Tao , Oleg Nesterov , Tetsuo Handa , David Rientjes , LKML , Michal Hocko Michal Hocko wrote: > So there is a race window when some threads > won't have fatal_signal_pending while the oom_reaper could start > unmapping the address space. generic_perform_write could then write > zero page to the page cache and corrupt data. Oh, simple generic_perform_write() ? > > The race window is rather small and close to impossible to happen but it > would be better to have it covered. OK, I confirmed that this problem is easily reproducible using below reproducer. ---------- #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #define NUMTHREADS 512 #define STACKSIZE 8192 static int pipe_fd[2] = { EOF, EOF }; static int file_writer(void *i) { char buffer[4096] = { }; int fd; snprintf(buffer, sizeof(buffer), "/tmp/file.%lu", (unsigned long) i); fd = open(buffer, O_WRONLY | O_CREAT | O_APPEND, 0600); memset(buffer, 0xFF, sizeof(buffer)); read(pipe_fd[0], buffer, 1); while (write(fd, buffer, sizeof(buffer)) == sizeof(buffer)); return 0; } int main(int argc, char *argv[]) { char *buf = NULL; unsigned long size; unsigned long i; char *stack; if (pipe(pipe_fd)) return 1; stack = malloc(STACKSIZE * NUMTHREADS); for (size = 1048576; size < 512UL * (1 << 30); size <<= 1) { char *cp = realloc(buf, size); if (!cp) { size >>= 1; break; } buf = cp; } for (i = 0; i < NUMTHREADS; i++) if (clone(file_writer, stack + (i + 1) * STACKSIZE, CLONE_THREAD | CLONE_SIGHAND | CLONE_VM | CLONE_FS | CLONE_FILES, (void *) i) == -1) break; close(pipe_fd[1]); /* Will cause OOM due to overcommit; if not use SysRq-f */ for (i = 0; i < size; i += 4096) buf[i] = 0; kill(-1, SIGKILL); return 0; } ---------- $ cat /tmp/file.* | od -b | head 0000000 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 * 307730000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 * 307740000 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 * 316600000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 * 316610000 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 * ---------- Applying your patch seems to avoid this problem, but as far as I tested your patch seems to trivially trigger something lock related problem. Is your patch really safe? Complete log is at http://I-love.SAKURA.ne.jp/tmp/serial-20170804.txt.xz and config is at http://I-love.SAKURA.ne.jp/tmp/config-20170804 . ---------- [ 58.539455] Out of memory: Kill process 1056 (a.out) score 603 or sacrifice child [ 58.543943] Killed process 1056 (a.out) total-vm:4268108kB, anon-rss:2246048kB, file-rss:0kB, shmem-rss:0kB [ 58.544245] a.out (1169) used greatest stack depth: 11664 bytes left [ 58.557471] DEBUG_LOCKS_WARN_ON(depth <= 0) [ 58.557480] ------------[ cut here ]------------ [ 58.564407] WARNING: CPU: 6 PID: 1339 at kernel/locking/lockdep.c:3617 lock_release+0x172/0x1e0 [ 58.569076] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_rpfilter ipt_REJECT nf_reject_ipv4 ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_nat ebtable_broute bridge stp llc ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_raw ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter coretemp ppdev pcspkr vmw_balloon vmw_vmci shpchp sg i2c_piix4 parport_pc parport ip_tables xfs libcrc32c sr_mod sd_mod cdrom ata_generic pata_acpi serio_raw mptspi scsi_transport_spi mptscsih ahci e1000 libahci ata_piix mptbase libata [ 58.599401] CPU: 6 PID: 1339 Comm: a.out Not tainted 4.13.0-rc3-next-20170803+ #142 [ 58.604126] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015 [ 58.609790] task: ffff9d90df888040 task.stack: ffffa07084854000 [ 58.613944] RIP: 0010:lock_release+0x172/0x1e0 [ 58.617622] RSP: 0000:ffffa07084857e58 EFLAGS: 00010082 [ 58.621533] RAX: 000000000000001f RBX: ffff9d90df888040 RCX: 0000000000000000 [ 58.626074] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffa30d4ba4 [ 58.630572] RBP: ffffa07084857e98 R08: 0000000000000000 R09: 0000000000000001 [ 58.635016] R10: 0000000000000000 R11: 000000000000001f R12: ffffa07084857f58 [ 58.639694] R13: ffff9d90f60d6cd0 R14: 0000000000000000 R15: ffffffffa305cb6e [ 58.644200] FS: 00007fb932730740(0000) GS:ffff9d90f9f80000(0000) knlGS:0000000000000000 [ 58.648989] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 58.652903] CR2: 000000000040092f CR3: 0000000135229000 CR4: 00000000000606e0 [ 58.657280] Call Trace: [ 58.659989] up_read+0x1a/0x40 [ 58.662825] __do_page_fault+0x28e/0x4c0 [ 58.665946] do_page_fault+0x30/0x80 [ 58.668911] page_fault+0x28/0x30 [ 58.671629] RIP: 0033:0x40092f [ 58.674221] RSP: 002b:00007fb931f99ff0 EFLAGS: 00010217 [ 58.677556] RAX: 0000000000001000 RBX: 00007fb931f99ff0 RCX: 00007fb93224ec90 [ 58.681489] RDX: 0000000000001000 RSI: 00007fb931f99ff0 RDI: 0000000000000117 [ 58.685297] RBP: 0000000000000117 R08: 00007fb9321ae938 R09: 000000000000000d [ 58.689123] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000100000000 [ 58.692879] R13: 00007fb731f59010 R14: 0000000000000000 R15: 00007fb731f59010 [ 58.696588] Code: 5e 41 5f 5d c3 e8 df a7 26 00 85 c0 74 1f 8b 35 2d 2f df 01 85 f6 75 15 48 c7 c6 66 7c a0 a3 48 c7 c7 5b 41 a0 a3 e8 6a 14 01 00 <0f> ff 4c 89 fa 4c 89 ee 48 89 df e8 fe c8 ff ff eb 88 48 c7 c7 [ 58.705635] ---[ end trace 91ff0f99e79ee485 ]--- [ 58.831028] oom_reaper: reaped process 1056 (a.out), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB ---------- ---------- [ 187.202689] Out of memory: Kill process 2113 (a.out) score 734 or sacrifice child [ 187.208024] Killed process 2113 (a.out) total-vm:4268108kB, anon-rss:2735276kB, file-rss:0kB, shmem-rss:0kB [ 187.463902] oom_reaper: reaped process 2113 (a.out), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB [ 188.249973] DEBUG_LOCKS_WARN_ON(depth <= 0) [ 188.249983] ------------[ cut here ]------------ [ 188.257247] WARNING: CPU: 7 PID: 2313 at kernel/locking/lockdep.c:3617 lock_release+0x172/0x1e0 [ 188.263282] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_rpfilter ipt_REJECT nf_reject_ipv4 ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_nat ebtable_broute bridge stp llc ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_raw ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter coretemp pcspkr vmw_balloon ppdev i2c_piix4 vmw_vmci shpchp sg parport_pc parport ip_tables xfs libcrc32c sr_mod sd_mod cdrom ata_generic pata_acpi serio_raw mptspi scsi_transport_spi ahci mptscsih ata_piix libahci e1000 mptbase libata [ 188.295888] CPU: 7 PID: 2313 Comm: a.out Not tainted 4.13.0-rc3-next-20170803+ #142 [ 188.300975] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015 [ 188.307049] task: ffff8c4433840040 task.stack: ffff9459c660c000 [ 188.311510] RIP: 0010:lock_release+0x172/0x1e0 [ 188.315530] RSP: 0000:ffff9459c660fe58 EFLAGS: 00010082 [ 188.319895] RAX: 000000000000001f RBX: ffff8c4433840040 RCX: 0000000000000000 [ 188.324908] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff810d4ba4 [ 188.329894] RBP: ffff9459c660fe98 R08: 0000000000000000 R09: 0000000000000001 [ 188.334724] R10: 0000000000000000 R11: 000000000000001f R12: ffff9459c660ff58 [ 188.339707] R13: ffff8c4434644c90 R14: 0000000000000000 R15: ffffffff8105cb6e [ 188.344553] FS: 00007f0e2aca8740(0000) GS:ffff8c4439fc0000(0000) knlGS:0000000000000000 [ 188.349616] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 188.353835] CR2: 00007f0e2a665ff0 CR3: 00000001346a5005 CR4: 00000000000606e0 [ 188.358604] Call Trace: [ 188.361539] up_read+0x1a/0x40 [ 188.364661] __do_page_fault+0x28e/0x4c0 [ 188.368059] do_page_fault+0x30/0x80 [ 188.371338] page_fault+0x28/0x30 [ 188.374426] RIP: 0033:0x7f0e2a7c6c90 [ 188.377543] RSP: 002b:00007f0e2a46bfe8 EFLAGS: 00010246 [ 188.381238] RAX: 0000000000001000 RBX: 00007f0e2a46bff0 RCX: 00007f0e2a7c6c90 [ 188.385576] RDX: 0000000000001000 RSI: 00007f0e2a46bff0 RDI: 00000000000000fd [ 188.389886] RBP: 00000000000000fd R08: 00007f0e2a726938 R09: 000000000000000d [ 188.394148] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000100000000 [ 188.398339] R13: 00007f0c2a4d1010 R14: 0000000000000000 R15: 00007f0c2a4d1010 [ 188.402508] Code: 5e 41 5f 5d c3 e8 df a7 26 00 85 c0 74 1f 8b 35 2d 2f df 01 85 f6 75 15 48 c7 c6 66 7c a0 81 48 c7 c7 5b 41 a0 81 e8 6a 14 01 00 <0f> ff 4c 89 fa 4c 89 ee 48 89 df e8 fe c8 ff ff eb 88 48 c7 c7 [ 188.412704] ---[ end trace d42863c48bb12d0a ]--- ---------- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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