WARNING in xfrm_state_fini (2)

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
4bf772b14675411a69b3c807f73006de0fe4b649 (Fri Feb 2 01:48:47 2018 +0000)
Merge tag 'drm-for-v4.16' of git://people.freedesktop.org/~airlied/linux

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
user-space arch: i386

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0bf051...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

netlink: 3 bytes leftover after parsing attributes in process
`syz-executor2'.
WARNING: CPU: 0 PID: 28 at net/xfrm/xfrm_state.c:2341
xfrm_state_fini+0x46a/0x620 net/xfrm/xfrm_state.c:2341
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 28 Comm: kworker/u4:2 Not tainted 4.15.0+ #202
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1dc/0x200 kernel/panic.c:547
report_bug+0x211/0x2d0 lib/bug.c:184
fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
fixup_bug arch/x86/kernel/traps.c:247 [inline]
do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1097
RIP: 0010:xfrm_state_fini+0x46a/0x620 net/xfrm/xfrm_state.c:2341
RSP: 0000:ffff8801d993f148 EFLAGS: 00010293
RAX: ffff8801d9926000 RBX: ffff8801b899a100 RCX: ffffffff84be327a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff86ac93f8
RBP: ffff8801d993f2a0 R08: 1ffff1003b327dbc R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1003b327e2b
R13: ffff8801d993f278 R14: 1ffff1003b327e2f R15: ffff8801b899b500
xfrm_net_exit+0x25/0x70 net/xfrm/xfrm_policy.c:2978
ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
cleanup_net+0x6a3/0xcc0 net/core/net_namespace.c:517
process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
worker_thread+0x223/0x1990 kernel/workqueue.c:2247
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:542
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

syzbot has found reproducer for the following crash on net-next commit
ba6056a41cb09575a5ffe2fcfa9a0afb1b60eb92 (Mon Feb 26 15:37:24 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

So far this crash happened 165 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.

Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0bf051...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed.

WARNING: CPU: 1 PID: 21 at net/xfrm/xfrm_state.c:2341

xfrm_state_fini+0x46a/0x620 net/xfrm/xfrm_state.c:2341
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 21 Comm: kworker/u4:1 Not tainted 4.16.0-rc2+ #242

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]

dump_stack+0x194/0x24d lib/dump_stack.c:53

panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1dc/0x200 kernel/panic.c:547
report_bug+0x211/0x2d0 lib/bug.c:184
fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
fixup_bug arch/x86/kernel/traps.c:247 [inline]
do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315

invalid_op+0x58/0x80 arch/x86/entry/entry_64.S:957

RIP: 0010:xfrm_state_fini+0x46a/0x620 net/xfrm/xfrm_state.c:2341

RSP: 0018:ffff8801d9447150 EFLAGS: 00010293
RAX: ffff8801d9436580 RBX: ffff8801cd526200 RCX: ffffffff84e9ea7a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff86ec96b8
RBP: ffff8801d94472a8 R08: 1ffff1003b288dbd R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1003b288e2c
R13: ffff8801d9447280 R14: 1ffff1003b288e30 R15: ffff8801cd527600
xfrm_net_exit+0x25/0x70 net/xfrm/xfrm_policy.c:2978
ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:146
cleanup_net+0x5a3/0xbf0 net/core/net_namespace.c:539

process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
worker_thread+0x223/0x1990 kernel/workqueue.c:2247
kthread+0x33c/0x400 kernel/kthread.c:238

ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:407

[Jason Litzinger]

I've simplified the reproducer provided by syzbot to the included
version.  The warning is reproduced 100% using the qemu image in the
syzkaller docs running the latest upstream and net.

As noted on the dashboard, this is similar to [1], in that an entry
remains in the xfrm_state_walk list, but different because the
protocol is not 0, it is 43, IPPROTO_ROUTING (and is valid by the fix
for [1], see 6a53b7593233).

Unfortunately, when a namespace exits, xfrm_state_fini only flushes
IPSEC protocols.  I don't have enough experience with the xfrm
subsystem to know whether this is correct, however, dc00a525603650a14
explicitly allows non ipsec protocols, as well as 0 for "all".

Would it be more appropriate for flush to also flush the non ipsec

protocols allowed in xfrm_user.c:validate_tmpl (explicitly or with 0)?

If someone with more experience with the subsystem believes that to be
the case I'm happy to send a patch (against net or ipsec?), otherwise
I'm going to keep digging to see if a better option presents itself.

Regardless I hope the simplified reproducer might be useful.

-Jason

[1] https://syzkaller.appspot.com/bug?id=c922592229951800c197ce48a5eaab8877c33723

* I wasn't subscribed to the list for the original message, so I'm
  using the GUI to reply...apologies if anything is mangled.

[Dmitry Vyukov]

+kernel developers back to CC

Jason did some debugging of this bug and have some questions as to
what's the best way to proceed. Please read the above.

[Steffen Klassert]

Thanks for the info!

I'm traveling currently, so it may take some time
until I can look at it.