KMSAN: uninit-value in rds_connect

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 2dca2cbde67a kmsan: fix build warnings with CONFIG_KMSAN=n
git tree: https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=1519734a400000
kernel config: https://syzkaller.appspot.com/x/.config?x=820d6393634b55e3
dashboard link: https://syzkaller.appspot.com/bug?extid=0049bebbf3042dbd2e8f
compiler: clang version 8.0.0 (trunk 339414)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0049be...@syzkaller.appspotmail.com

RDX: 0000000000000000 RSI: 0000000020000380 RDI: 00000000000001ff
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00000000004cd2e8 R14: 00000000004c3d93 R15: 0000000000000003
==================================================================
BUG: KMSAN: uninit-value in rds_connect+0x213/0x950 net/rds/af_rds.c:511
CPU: 0 PID: 8117 Comm: syz-executor6 Not tainted 4.19.0-rc1+ #36
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
rds_connect+0x213/0x950 net/rds/af_rds.c:511
__sys_connect+0x64e/0x750 net/socket.c:1662
__do_sys_connect net/socket.c:1673 [inline]
__se_sys_connect net/socket.c:1670 [inline]
__x64_sys_connect+0xd8/0x120 net/socket.c:1670
do_syscall_64+0x15b/0x220 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x457089
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7090fc1c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f7090fc26d4 RCX: 0000000000457089
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cb710 R14: 00000000004c320b R15: 0000000000000000

Local variable description: ----address@__sys_connect
Variable was created at:
__sys_connect+0x6a/0x750 net/socket.c:1645
__do_sys_connect net/socket.c:1673 [inline]
__se_sys_connect net/socket.c:1670 [inline]
__x64_sys_connect+0xd8/0x120 net/socket.c:1670
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot.

[Santosh Shilimkar]

On 8/30/2018 11:31 AM, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    2dca2cbde67a kmsan: fix build warnings with CONFIG_KMSAN=n
> git tree:       https://github.com/google/kmsan.git/master
> console output: https://syzkaller.appspot.com/x/log.txt?x=1519734a400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=820d6393634b55e3
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=0049bebbf3042dbd2e8f
> compiler:       clang version 8.0.0 (trunk 339414)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+0049be...@syzkaller.appspotmail.com
>

OK. Will send the fix to address this.

Regards,
Santosh

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 25114c64b719 kmsan: unpoison pages moved from iov_iter to ..
git tree: https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=14465da6400000
kernel config: https://syzkaller.appspot.com/x/.config?x=3431f03869413153

dashboard link: https://syzkaller.appspot.com/bug?extid=0049bebbf3042dbd2e8f
compiler: clang version 8.0.0 (trunk 339414)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13b8513e400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10d64e96400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0049be...@syzkaller.appspotmail.com

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 rds_connect+0x213/0x950 net/rds/af_rds.c:511

CPU: 0 PID: 4780 Comm: syz-executor239 Not tainted 4.19.0-rc1+ #38

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
rds_connect+0x213/0x950 net/rds/af_rds.c:511
__sys_connect+0x64e/0x750 net/socket.c:1662
__do_sys_connect net/socket.c:1673 [inline]
__se_sys_connect net/socket.c:1670 [inline]
__x64_sys_connect+0xd8/0x120 net/socket.c:1670
do_syscall_64+0x15b/0x220 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x63/0xe7

RIP: 0033:0x440199
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:00007fff5f41c118 EFLAGS: 00000213 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440199
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401a20
R13: 0000000000401ab0 R14: 0000000000000000 R15: 0000000000000000

[syzbot]

> #syz test:
> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git master

KMSAN bugs can only be tested on https://github.com/google/kmsan.git tree
because KMSAN tool is not upstreamed yet.
See
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs
for details.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger
crash:

Reported-and-tested-by:
syzbot+0049be...@syzkaller.appspotmail.com

Tested on:

commit: 42a037ca8d9d kmsan: update README.md to reference LLVM r34..
git tree: https://github.com/google/kmsan.git/master
kernel config: https://syzkaller.appspot.com/x/.config?x=3431f03869413153

compiler: clang version 8.0.0 (trunk 339414)

patch: https://syzkaller.appspot.com/x/patch.diff?x=17fc0cd1400000

Note: testing is done by a robot and is best-effort only.