On Thu, Sep 13, 2018 at 11:18 AM syzbot <syzbot+2dcfeaf8cb49b05e8f1a@xxxxxxxxxxxxxxxxxxxxxxxxx> 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=1249fcb8400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=848e40757852af3e > dashboard link: https://syzkaller.appspot.com/bug?extid=2dcfeaf8cb49b05e8f1a > compiler: clang version 7.0.0 (trunk 334104) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=116ef050400000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=122870ff800000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+2dcfeaf8cb49b05e8f1a@xxxxxxxxxxxxxxxxxxxxxxxxx > > random: sshd: uninitialized urandom read (32 bytes read) > ================================================================== > 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: 0000000000000000 > 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 > ================================================================== This particular report was caused by the repro program writing a byte to /dev/nullb0 and /sbin/blkid reading from that device in the background. But it turns out that simply running `cat /dev/nullb0` already prints uninitialized kernel memory. Is this the intended behavior of the null block driver? > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > syzbot. > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/00000000000016eb330575bd2fab%40google.com. > For more options, visit https://groups.google.com/d/optout. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
