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[209.85.220.65]) by mx.google.com with SMTPS id z14sor1027278vsp.5.2019.05.15.07.41.56 for (Google Transport Security); Wed, 15 May 2019 07:41:56 -0700 (PDT) Received-SPF: pass (google.com: domain of glider@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=fja1SAdn; spf=pass (google.com: domain of glider@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=glider@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=kyqrOi+JSDiqriYxvI1BLUk2O3fUbri6hLyp92DBSeE=; b=fja1SAdncJKzVEpsr6jccnpaV7vbGu5OCk0r9Je+XDP9UpjODRhjIfaT31oqvm2LlN DCg4uj+LmtnjOnOsn96zCTA8Q0MHlfxH8P2yQjZjJjxtag9efgMXfYKz8beigXzpf3/+ X/SMUrBGInK43TFKnXnfH5J88/1azv/KulaF4RlNxIcRcgdpjppZwNMwBPq7do2SHkmc qXUT/T6XAofGuoRK18+100QF5mWi1dbmPcI/eg5rGh6CK92wWKZnqgt9K0QSH8O/1mol 5YUkVI0lGmPXn736aUaIAsXzQAJz5bRFZSs/lSktPXPEBQEezWEibFTE7raxdRYAJgSA 65ig== X-Google-Smtp-Source: APXvYqxvU/yjs/eG1W5tPjt2ohsn6xjNIutmqtITlHpOqtZGM2YjzMYaVrPb1QCfoOmFOnxtHPG6P5O1efiCK2jnK3c= X-Received: by 2002:a67:7241:: with SMTP id n62mr19856742vsc.217.1557931315562; Wed, 15 May 2019 07:41:55 -0700 (PDT) MIME-Version: 1.0 References: <00000000000016eb330575bd2fab@google.com> <06a3b403-7fe3-24fd-0ce2-9a604f3bbe62@kernel.dk> In-Reply-To: From: Alexander Potapenko Date: Wed, 15 May 2019 16:41:44 +0200 Message-ID: Subject: Re: KMSAN: kernel-infoleak in copy_page_to_iter (2) To: Jens Axboe Cc: Andrew Morton , bart.vanassche@wdc.com, matias.bjorling@wdc.com, Andi Kleen , jack@suse.cz, jlayton@redhat.com, LKML , Linux Memory Management List , mawilcox@microsoft.com, mgorman@techsingularity.net, syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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: From: Alexander Potapenko Date: Wed, Jan 2, 2019 at 11:09 AM To: Jens Axboe Cc: Andrew Morton, , , Andi Kleen, , , LKML, Linux Memory Management List, , , > On Wed, Dec 19, 2018 at 2:23 PM Jens Axboe wrote: > > > > On 12/19/18 3:23 AM, Alexander Potapenko wrote: > > > On Thu, Sep 13, 2018 at 11:23 AM Alexander Potapenko wrote: > > >> > > >> On Thu, Sep 13, 2018 at 11:18 AM syzbot > > >> wrote: > > >>> > > >>> Hello, > > >>> > > >>> syzbot found the following crash on: > > >>> > > >>> HEAD commit: 123906095e30 kmsan: introduce kmsan_interrupt_enter= ()/kmsa.. > > >>> git tree: https://github.com/google/kmsan.git/master > > >>> console output: https://syzkaller.appspot.com/x/log.txt?x=3D1249fcb= 8400000 > > >>> kernel config: https://syzkaller.appspot.com/x/.config?x=3D848e407= 57852af3e > > >>> dashboard link: https://syzkaller.appspot.com/bug?extid=3D2dcfeaf8c= b49b05e8f1a > > >>> compiler: clang version 7.0.0 (trunk 334104) > > >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D116ef= 050400000 > > >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D122870f= f800000 > > >>> > > >>> IMPORTANT: if you fix the bug, please add the following tag to the = commit: > > >>> Reported-by: syzbot+2dcfeaf8cb49b05e8f1a@syzkaller.appspotmail.com > > >>> > > >>> random: sshd: uninitialized urandom read (32 bytes read) > > >>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > >>> BUG: KMSAN: kernel-infoleak in copyout lib/iov_iter.c:140 [inline] > > >>> BUG: KMSAN: kernel-infoleak in copy_page_to_iter_iovec lib/iov_iter= .c:212 > > >>> [inline] > > >>> BUG: KMSAN: kernel-infoleak in copy_page_to_iter+0x754/0x1b70 > > >>> lib/iov_iter.c:716 > > >>> CPU: 0 PID: 4516 Comm: blkid Not tainted 4.17.0+ #9 > > >>> Hardware name: Google Google Compute Engine/Google Compute Engine, = BIOS > > >>> Google 01/01/2011 > > >>> Call Trace: > > >>> __dump_stack lib/dump_stack.c:77 [inline] > > >>> dump_stack+0x185/0x1d0 lib/dump_stack.c:113 > > >>> kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1125 > > >>> kmsan_internal_check_memory+0x17e/0x1f0 mm/kmsan/kmsan.c:1238 > > >>> kmsan_copy_to_user+0x7a/0x160 mm/kmsan/kmsan.c:1261 > > >>> copyout lib/iov_iter.c:140 [inline] > > >>> copy_page_to_iter_iovec lib/iov_iter.c:212 [inline] > > >>> copy_page_to_iter+0x754/0x1b70 lib/iov_iter.c:716 > > >>> generic_file_buffered_read mm/filemap.c:2185 [inline] > > >>> generic_file_read_iter+0x2ef8/0x44d0 mm/filemap.c:2362 > > >>> blkdev_read_iter+0x20d/0x280 fs/block_dev.c:1930 > > >>> call_read_iter include/linux/fs.h:1778 [inline] > > >>> new_sync_read fs/read_write.c:406 [inline] > > >>> __vfs_read+0x775/0x9d0 fs/read_write.c:418 > > >>> vfs_read+0x36c/0x6b0 fs/read_write.c:452 > > >>> ksys_read fs/read_write.c:578 [inline] > > >>> __do_sys_read fs/read_write.c:588 [inline] > > >>> __se_sys_read fs/read_write.c:586 [inline] > > >>> __x64_sys_read+0x1bf/0x3e0 fs/read_write.c:586 > > >>> do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287 > > >>> entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > >>> RIP: 0033:0x7fdeff68f310 > > >>> RSP: 002b:00007ffe999660b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000= 000 > > >>> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fdeff68f310 > > >>> RDX: 0000000000000100 RSI: 0000000001e78df8 RDI: 0000000000000003 > > >>> RBP: 0000000001e78dd0 R08: 0000000000000028 R09: 0000000001680000 > > >>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001e78030 > > >>> R13: 0000000000000100 R14: 0000000001e78080 R15: 0000000001e78de8 > > >>> > > >>> Uninit was created at: > > >>> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:282 [inline] > > >>> kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:819 > > >>> kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:889 > > >>> __alloc_pages_nodemask+0xf7b/0x5cc0 mm/page_alloc.c:4402 > > >>> alloc_pages_current+0x6b1/0x970 mm/mempolicy.c:2093 > > >>> alloc_pages include/linux/gfp.h:494 [inline] > > >>> __page_cache_alloc+0x95/0x320 mm/filemap.c:946 > > >>> pagecache_get_page+0x52b/0x1450 mm/filemap.c:1577 > > >>> grab_cache_page_write_begin+0x10d/0x190 mm/filemap.c:3089 > > >>> block_write_begin+0xf9/0x3a0 fs/buffer.c:2068 > > >>> blkdev_write_begin+0xf5/0x110 fs/block_dev.c:584 > > >>> generic_perform_write+0x438/0x9d0 mm/filemap.c:3139 > > >>> __generic_file_write_iter+0x43b/0xa10 mm/filemap.c:3264 > > >>> blkdev_write_iter+0x3a8/0x5f0 fs/block_dev.c:1910 > > >>> do_iter_readv_writev+0x81c/0xa20 include/linux/fs.h:1778 > > >>> do_iter_write+0x30d/0xd50 fs/read_write.c:959 > > >>> vfs_writev fs/read_write.c:1004 [inline] > > >>> do_writev+0x3be/0x820 fs/read_write.c:1039 > > >>> __do_sys_writev fs/read_write.c:1112 [inline] > > >>> __se_sys_writev fs/read_write.c:1109 [inline] > > >>> __x64_sys_writev+0xe1/0x120 fs/read_write.c:1109 > > >>> do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287 > > >>> entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > >>> > > >>> Bytes 4-255 of 256 are uninitialized > > >>> Memory access starts at ffff8801b9903000 > > >>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > >> This particular report was caused by the repro program writing a byt= e > > >> to /dev/nullb0 and /sbin/blkid reading from that device in the > > >> background. > > >> But it turns out that simply running `cat /dev/nullb0` already print= s > > >> uninitialized kernel memory. > > >> Is this the intended behavior of the null block driver? > > > A friendly ping, this bug is still reproducible on syzbot. > > > > Does this fix it? > There must be something wrong with my tool, as it stops reporting this > bug when I apply your patch. > However when I run `cat /dev/nullb0 | strings` and wait long enough I > start seeing meaningful strings (file names, env dumps etc.) > I suspect this is still unexpected, right? A friendly ping, as we're still seeing similar errors. > > diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_mai= n.c > > index 62c9654b9ce8..08808c572692 100644 > > --- a/drivers/block/null_blk_main.c > > +++ b/drivers/block/null_blk_main.c > > @@ -655,7 +655,7 @@ static struct nullb_page *null_alloc_page(gfp_t gfp= _flags) > > if (!t_page) > > goto out; > > > > - t_page->page =3D alloc_pages(gfp_flags, 0); > > + t_page->page =3D alloc_pages(gfp_flags | __GFP_ZERO, 0); > > if (!t_page->page) > > goto out_freepage; > > > > > > -- > > Jens Axboe > > > > > -- > Alexander Potapenko > Software Engineer > > Google Germany GmbH > Erika-Mann-Stra=C3=9Fe, 33 > 80636 M=C3=BCnchen > > Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Halimah DeLaine Prado > Registergericht und -nummer: Hamburg, HRB 86891 > Sitz der Gesellschaft: Hamburg --=20 Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg