Subject: KMSAN: uninit-value in ip6_compressed_string

From: syzbot <[email-masked]>
Date: Wed, 28 Nov 2018 09:40:03 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    fffec98ae2a6 net: proper support for CONFIG_GENERIC_CSUM o..
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=156ad1f5400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=56b48b46dafe4516
dashboard link: https://syzkaller.appspot.com/bug?extid=047a11c361b872896a4f
compiler:       clang version 8.0.0 (trunk 343298)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1031326d400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16212b0b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KMSAN: uninit-value in ip6_compressed_string+0x1a9/0x1460  
lib/vsprintf.c:1161
CPU: 1 PID: 6762 Comm: syz-executor445 Not tainted 4.20.0-rc3+ #95
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+0x32d/0x480 lib/dump_stack.c:113
  kmsan_report+0x12c/0x290 mm/kmsan/kmsan.c:683
  __msan_warning+0x76/0xc0 mm/kmsan/kmsan_instr.c:330
  ip6_compressed_string+0x1a9/0x1460 lib/vsprintf.c:1161
  ip6_addr_string+0x165/0x2b0 lib/vsprintf.c:1247
  pointer+0x110e/0x1520 lib/vsprintf.c:1911
  vsnprintf+0xabf/0x3110 lib/vsprintf.c:2300
  snprintf+0x246/0x290 lib/vsprintf.c:2429
  rpc_ntop6_noscopeid net/sunrpc/addr.c:56 [inline]
  rpc_sockaddr2uaddr+0x3aa/0x6f0 net/sunrpc/addr.c:281
  rpcb_getport_async+0x10d4/0x1770 net/sunrpc/rpcb_clnt.c:773
  call_bind+0x1a8/0x260 net/sunrpc/clnt.c:1802
  __rpc_execute+0xacb/0x19c0 net/sunrpc/sched.c:832
  rpc_execute+0x6ad/0x940 net/sunrpc/sched.c:900
  rpc_run_task+0xc42/0xe70 net/sunrpc/clnt.c:1065
  rpc_call_sync net/sunrpc/clnt.c:1094 [inline]
  rpc_ping net/sunrpc/clnt.c:2516 [inline]
  rpc_create_xprt+0x6a9/0xe80 net/sunrpc/clnt.c:480
  rpc_create+0xa78/0xb30 net/sunrpc/clnt.c:588
  nfs_create_rpc_client+0x752/0x860 fs/nfs/client.c:523
  nfs_init_client+0xb8/0x1d0 fs/nfs/client.c:634
  nfs_get_client+0x14fc/0x1720 fs/nfs/client.c:425
  nfs_init_server fs/nfs/client.c:670 [inline]
  nfs_create_server+0xbd7/0x3290 fs/nfs/client.c:954
  nfs_try_mount+0x4de/0x14b0 fs/nfs/super.c:1884
  nfs_fs_mount+0x393d/0x4000 fs/nfs/super.c:2695
  mount_fs+0x282/0x790 fs/super.c:1261
  vfs_kern_mount+0x231/0x8c0 fs/namespace.c:961
  do_new_mount fs/namespace.c:2469 [inline]
  do_mount+0xd1f/0x5ac0 fs/namespace.c:2801
  ksys_mount+0x32e/0x3d0 fs/namespace.c:3017
  __do_sys_mount fs/namespace.c:3031 [inline]
  __se_sys_mount+0xe5/0x110 fs/namespace.c:3028
  __x64_sys_mount+0x62/0x80 fs/namespace.c:3028
  do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x4401c9
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:00007fff7eefaf48 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00000000004401c9
RDX: 0000000020000180 RSI: 0000000020000140 RDI: 0000000000000000
RBP: 00000000006ca018 R08: 000000002000a000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000401a50
R13: 0000000000401ae0 R14: 0000000000000000 R15: 0000000000000000

Uninit was stored to memory at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:246 [inline]
  kmsan_save_stack mm/kmsan/kmsan.c:261 [inline]
  kmsan_internal_chain_origin+0x13d/0x240 mm/kmsan/kmsan.c:469
  kmsan_memcpy_memmove_metadata+0x1a9/0xf70 mm/kmsan/kmsan.c:344
  kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:362
  __msan_memcpy+0x61/0x70 mm/kmsan/kmsan_instr.c:162
  ip6_compressed_string+0x89/0x1460 lib/vsprintf.c:1154
  ip6_addr_string+0x165/0x2b0 lib/vsprintf.c:1247
  pointer+0x110e/0x1520 lib/vsprintf.c:1911
  vsnprintf+0xabf/0x3110 lib/vsprintf.c:2300
  snprintf+0x246/0x290 lib/vsprintf.c:2429
  rpc_ntop6_noscopeid net/sunrpc/addr.c:56 [inline]
  rpc_sockaddr2uaddr+0x3aa/0x6f0 net/sunrpc/addr.c:281
  rpcb_getport_async+0x10d4/0x1770 net/sunrpc/rpcb_clnt.c:773
  call_bind+0x1a8/0x260 net/sunrpc/clnt.c:1802
  __rpc_execute+0xacb/0x19c0 net/sunrpc/sched.c:832
  rpc_execute+0x6ad/0x940 net/sunrpc/sched.c:900
  rpc_run_task+0xc42/0xe70 net/sunrpc/clnt.c:1065
  rpc_call_sync net/sunrpc/clnt.c:1094 [inline]
  rpc_ping net/sunrpc/clnt.c:2516 [inline]
  rpc_create_xprt+0x6a9/0xe80 net/sunrpc/clnt.c:480
  rpc_create+0xa78/0xb30 net/sunrpc/clnt.c:588
  nfs_create_rpc_client+0x752/0x860 fs/nfs/client.c:523
  nfs_init_client+0xb8/0x1d0 fs/nfs/client.c:634
  nfs_get_client+0x14fc/0x1720 fs/nfs/client.c:425
  nfs_init_server fs/nfs/client.c:670 [inline]
  nfs_create_server+0xbd7/0x3290 fs/nfs/client.c:954
  nfs_try_mount+0x4de/0x14b0 fs/nfs/super.c:1884
  nfs_fs_mount+0x393d/0x4000 fs/nfs/super.c:2695
  mount_fs+0x282/0x790 fs/super.c:1261
  vfs_kern_mount+0x231/0x8c0 fs/namespace.c:961
  do_new_mount fs/namespace.c:2469 [inline]
  do_mount+0xd1f/0x5ac0 fs/namespace.c:2801
  ksys_mount+0x32e/0x3d0 fs/namespace.c:3017
  __do_sys_mount fs/namespace.c:3031 [inline]
  __se_sys_mount+0xe5/0x110 fs/namespace.c:3028
  __x64_sys_mount+0x62/0x80 fs/namespace.c:3028
  do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291
  entry_SYSCALL_64_after_hwframe+0x63/0xe7

Local variable description: ----addr@rpcb_getport_async
Variable was created at:
  rpcb_getport_async+0xb3/0x1770 net/sunrpc/rpcb_clnt.c:673
  call_bind+0x1a8/0x260 net/sunrpc/clnt.c:1802
==================================================================

---
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