WARNING in hwsim_new_radio_nl

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 5d30bcac Merge tag '9p-for-5.7-2' of git://github.com/mart..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=119383b3e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=65d386b867ba5289
dashboard link: https://syzkaller.appspot.com/bug?extid=a4aee3f42d7584d76761
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

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+a4aee3...@syzkaller.appspotmail.com

------------[ cut here ]------------
precision 33020 too large
WARNING: CPU: 0 PID: 25816 at lib/vsprintf.c:2471 set_precision lib/vsprintf.c:2471 [inline]
WARNING: CPU: 0 PID: 25816 at lib/vsprintf.c:2471 vsnprintf+0x1467/0x1aa0 lib/vsprintf.c:2547
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 25816 Comm: syz-executor.0 Not tainted 5.6.0-syzkaller #0
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+0x1e9/0x30e lib/dump_stack.c:118
panic+0x264/0x7a0 kernel/panic.c:221
__warn+0x209/0x210 kernel/panic.c:582
report_bug+0x1ac/0x2d0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:175 [inline]
do_error_trap+0xca/0x1c0 arch/x86/kernel/traps.c:267
do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:set_precision lib/vsprintf.c:2471 [inline]
RIP: 0010:vsnprintf+0x1467/0x1aa0 lib/vsprintf.c:2547
Code: f5 6e f9 48 8d 5c 24 48 e9 8e fc ff ff e8 81 f5 6e f9 c6 05 a6 4e 63 01 01 48 c7 c7 c1 69 0a 89 44 89 fe 31 c0 e8 29 09 41 f9 <0f> 0b e9 b7 f6 ff ff e8 5d f5 6e f9 c6 05 81 4e 63 01 01 48 c7 c7
RSP: 0018:ffffc90016587780 EFLAGS: 00010246
RAX: 2f3b2aeaadea7400 RBX: ffffc900165877c8 RCX: 0000000000040000
RDX: ffffc90001f09000 RSI: 0000000000009177 RDI: 0000000000009178
RBP: 80fc0000ffffff02 R08: dffffc0000000000 R09: fffffbfff162889d
R10: fffffbfff162889d R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff88ea1fb0 R15: 00000000000080fc
kvasprintf+0x59/0xf0 lib/kasprintf.c:22
kasprintf+0x6a/0x90 lib/kasprintf.c:59
hwsim_new_radio_nl+0x95c/0xf30 drivers/net/wireless/mac80211_hwsim.c:3672
genl_family_rcv_msg_doit net/netlink/genetlink.c:673 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:718 [inline]
genl_rcv_msg+0x1054/0x1530 net/netlink/genetlink.c:735
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2469
genl_rcv+0x24/0x40 net/netlink/genetlink.c:746
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1329
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg net/socket.c:672 [inline]
____sys_sendmsg+0x4f9/0x7c0 net/socket.c:2362
___sys_sendmsg net/socket.c:2416 [inline]
__sys_sendmsg+0x2a6/0x360 net/socket.c:2449
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c889
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb9e5575c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb9e55766d4 RCX: 000000000045c889
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009f5 R14: 00000000004ccb09 R15: 000000000076bf0c
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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 syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 4f8a3cc1 Merge tag 'x86-urgent-2020-04-12' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=110243b3e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=3bfbde87e8e65624

dashboard link: https://syzkaller.appspot.com/bug?extid=a4aee3f42d7584d76761
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=100825afe00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10df613fe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a4aee3...@syzkaller.appspotmail.com

netlink: 98586 bytes leftover after parsing attributes in process `syz-executor425'.

------------[ cut here ]------------
precision 33020 too large

WARNING: CPU: 1 PID: 6998 at lib/vsprintf.c:2471 set_precision lib/vsprintf.c:2471 [inline]
WARNING: CPU: 1 PID: 6998 at lib/vsprintf.c:2471 vsnprintf+0x1467/0x1aa0 lib/vsprintf.c:2547

Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 6998 Comm: syz-executor425 Not tainted 5.6.0-syzkaller #0

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+0x1e9/0x30e lib/dump_stack.c:118
panic+0x264/0x7a0 kernel/panic.c:221
__warn+0x209/0x210 kernel/panic.c:582
report_bug+0x1ac/0x2d0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:175 [inline]
do_error_trap+0xca/0x1c0 arch/x86/kernel/traps.c:267
do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:set_precision lib/vsprintf.c:2471 [inline]
RIP: 0010:vsnprintf+0x1467/0x1aa0 lib/vsprintf.c:2547

Code: a6 bb fd 48 8d 5c 24 48 e9 8e fc ff ff e8 01 a6 bb fd c6 05 bf 06 b0 05 01 48 c7 c7 c1 d3 f2 88 44 89 fe 31 c0 e8 29 ba 8d fd <0f> 0b e9 b7 f6 ff ff e8 dd a5 bb fd c6 05 9a 06 b0 05 01 48 c7 c7
RSP: 0018:ffffc90001647780 EFLAGS: 00010246
RAX: 2f9f2ace1f35b900 RBX: ffffc900016477c8 RCX: ffff88809d86c2c0
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000286
RBP: 80fc0000ffffff02 R08: dffffc0000000000 R09: fffffbfff1628ea5
R10: fffffbfff1628ea5 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff88ea3058 R15: 00000000000080fc

kvasprintf+0x59/0xf0 lib/kasprintf.c:22
kasprintf+0x6a/0x90 lib/kasprintf.c:59
hwsim_new_radio_nl+0x95c/0xf30 drivers/net/wireless/mac80211_hwsim.c:3672
genl_family_rcv_msg_doit net/netlink/genetlink.c:673 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:718 [inline]
genl_rcv_msg+0x1054/0x1530 net/netlink/genetlink.c:735
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2469
genl_rcv+0x24/0x40 net/netlink/genetlink.c:746
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1329
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg net/socket.c:672 [inline]
____sys_sendmsg+0x4f9/0x7c0 net/socket.c:2362
___sys_sendmsg net/socket.c:2416 [inline]
__sys_sendmsg+0x2a6/0x360 net/socket.c:2449
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3

RIP: 0033:0x4401f9
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:00007ffecc373af8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401f9

RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003

RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a80
R13: 0000000000401b10 R14: 0000000000000000 R15: 0000000000000000

[syzbot]

syzbot has bisected this bug to:

commit 01cacb00b35cb62b139f07d5f84bcf0eeda8eff6
Author: Paolo Abeni <pab...@redhat.com>
Date: Fri Mar 27 21:48:51 2020 +0000

mptcp: add netlink-based PM

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10225bb3e00000
start commit: 4f8a3cc1 Merge tag 'x86-urgent-2020-04-12' of git://git.ke..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=12225bb3e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14225bb3e00000

kernel config: https://syzkaller.appspot.com/x/.config?x=3bfbde87e8e65624
dashboard link: https://syzkaller.appspot.com/bug?extid=a4aee3f42d7584d76761

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=100825afe00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10df613fe00000

Reported-by: syzbot+a4aee3...@syzkaller.appspotmail.com
Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Johannes Berg]

Hi syzbot keepers,

On Mon, 2020-04-13 at 07:05 -0700, syzbot wrote:
> syzbot has bisected this bug to:
>
> commit 01cacb00b35cb62b139f07d5f84bcf0eeda8eff6
> Author: Paolo Abeni <pab...@redhat.com>
> Date: Fri Mar 27 21:48:51 2020 +0000
>
> mptcp: add netlink-based PM
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10225bb3e00000

This is, fairly obviously, incorrect. Same with the bisection for
6693adf1698864d21734, which is really the same underlying problem as
this one (though at a different code site).

However, it stands out that this was bisected to a commit that adds a
new generic netlink family in both cases.

This makes sense - the reproducer identifies the family by *number*, but
that number isn't stable, generic netlink families should be identified
by *name*.

Perhaps somehow syzbot could be taught that, so that the bisection is
stable across kernels with different generic netlink families
registered?

Alternatively, we _could_ add some kind of stable ID mode, but I'm not
sure we really want to ... since that would mean people start hardcoding
IDs?

johannes

[Paolo Abeni]

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

I don't see why the bisection pointed to the MPTCP commit ?!? the
following patch should address the issue.
---
diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 7fe8207db6ae..2082abdb08d4 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -635,7 +635,8 @@ static const struct nla_policy hwsim_genl_policy[HWSIM_ATTR_MAX + 1] = {
[HWSIM_ATTR_SUPPORT_P2P_DEVICE] = { .type = NLA_FLAG },
[HWSIM_ATTR_USE_CHANCTX] = { .type = NLA_FLAG },
[HWSIM_ATTR_DESTROY_RADIO_ON_CLOSE] = { .type = NLA_FLAG },
- [HWSIM_ATTR_RADIO_NAME] = { .type = NLA_STRING },
+ [HWSIM_ATTR_RADIO_NAME] = { .type = NLA_STRING,
+ .len = NL80211_WIPHY_NAME_MAXLEN },
[HWSIM_ATTR_NO_VIF] = { .type = NLA_FLAG },
[HWSIM_ATTR_FREQ] = { .type = NLA_U32 },
[HWSIM_ATTR_TX_INFO_FLAGS] = { .type = NLA_BINARY },

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+a4aee3...@syzkaller.appspotmail.com

Tested on:

commit: e154659b mptcp: fix double-unlock in mptcp_poll
git tree: net
kernel config: https://syzkaller.appspot.com/x/.config?x=5af684c50f30bcb2

dashboard link: https://syzkaller.appspot.com/bug?extid=a4aee3f42d7584d76761
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

patch: https://syzkaller.appspot.com/x/patch.diff?x=144e124fe00000

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

[Johannes Berg]

On Tue, 2020-04-14 at 12:42 +0200, Paolo Abeni wrote:
> #syz test git://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git master
>
> I don't see why the bisection pointed to the MPTCP commit ?!?

I just sent an explanation for that :)

Good fix too, I already applied another one just now for an earlier, but
really mostly identical, syzbot warning (and yes, tagged it with both).

johannes

[Paolo Abeni]

On Tue, 2020-04-14 at 13:11 +0200, Johannes Berg wrote:
> On Tue, 2020-04-14 at 12:42 +0200, Paolo Abeni wrote:
> > #syz test git://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git master
> >
> > I don't see why the bisection pointed to the MPTCP commit ?!?
>
> I just sent an explanation for that :)

Thanks, I did not thought about hard-coded ids!

> Good fix too, I already applied another one just now for an earlier, but
> really mostly identical, syzbot warning (and yes, tagged it with both).

Nice! I saw the fix you mentioned after reading your email. I'm fine
with that.

Cheers,

Paolo

[Dmitry Vyukov]

+syzkaller mailing list

Hi Johannes,

syzkaller has a pseudo-syscall to map string genetlink family ID to
int ID. If that syscall would have been used, then I assume it should
have worked. However in this case, it managed to trigger the bug with
a plain opaque blob with no knowledge about the blob contents
whatsoever. I don't see any realistic way to preserve family ID in
this case.