syzbot

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KMSAN: uninit-value in btrfs_read_disk_super fs/btrfs/volumes.c:1198 [inline]
BUG: KMSAN: uninit-value in btrfs_scan_one_device+0x4c8/0x14e0 fs/btrfs/volumes.c:1241
CPU: 1 PID: 4744 Comm: syz-executor367 Not tainted 4.19.0-rc1+ #39
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+0x14b/0x190 lib/dump_stack.c:113
 kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:956
 __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:645
 btrfs_read_disk_super fs/btrfs/volumes.c:1198 [inline]
 btrfs_scan_one_device+0x4c8/0x14e0 fs/btrfs/volumes.c:1241
 btrfs_mount_root+0xcab/0x22e0 fs/btrfs/super.c:1566
 mount_fs+0x28f/0x760 fs/super.c:1261
 vfs_kern_mount+0x21b/0x8d0 fs/namespace.c:961
 btrfs_mount+0x8b2/0x2f40 fs/btrfs/super.c:1670
 mount_fs+0x28f/0x760 fs/super.c:1261
 vfs_kern_mount+0x21b/0x8d0 fs/namespace.c:961
 do_new_mount fs/namespace.c:2457 [inline]
 do_mount+0xcee/0x56b0 fs/namespace.c:2787
 ksys_mount+0x32e/0x3d0 fs/namespace.c:3003
 __do_sys_mount fs/namespace.c:3017 [inline]
 __se_sys_mount fs/namespace.c:3014 [inline]
 __x64_sys_mount+0x157/0x1c0 fs/namespace.c:3014
 do_syscall_64+0x15b/0x220 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x440029
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff9182cff8 EFLAGS: 00000217 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440029
RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000020000100
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004018b0
R13: 0000000000401940 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:256 [inline]
 kmsan_internal_alloc_meta_for_pages+0x146/0x700 mm/kmsan/kmsan.c:694
 kmsan_alloc_page+0x75/0xd0 mm/kmsan/kmsan_hooks.c:250
 __alloc_pages_nodemask+0xf6b/0x5c80 mm/page_alloc.c:4411
 alloc_pages_current+0x6b1/0x970 mm/mempolicy.c:2093
 alloc_pages include/linux/gfp.h:511 [inline]
 __page_cache_alloc+0x95/0x320 mm/filemap.c:946
 do_read_cache_page+0x829/0x1630 mm/filemap.c:2792
 read_cache_page_gfp+0xe9/0x120 mm/filemap.c:2914
 btrfs_read_disk_super fs/btrfs/volumes.c:1187 [inline]
 btrfs_scan_one_device+0x297/0x14e0 fs/btrfs/volumes.c:1241
 btrfs_mount_root+0xcab/0x22e0 fs/btrfs/super.c:1566
 mount_fs+0x28f/0x760 fs/super.c:1261
 vfs_kern_mount+0x21b/0x8d0 fs/namespace.c:961
 btrfs_mount+0x8b2/0x2f40 fs/btrfs/super.c:1670
 mount_fs+0x28f/0x760 fs/super.c:1261
 vfs_kern_mount+0x21b/0x8d0 fs/namespace.c:961
 do_new_mount fs/namespace.c:2457 [inline]
 do_mount+0xcee/0x56b0 fs/namespace.c:2787
 ksys_mount+0x32e/0x3d0 fs/namespace.c:3003
 __do_sys_mount fs/namespace.c:3017 [inline]
 __se_sys_mount fs/namespace.c:3014 [inline]
 __x64_sys_mount+0x157/0x1c0 fs/namespace.c:3014
 do_syscall_64+0x15b/0x220 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================