WARNING in netlink_ack (2)

[syzbot]

Hello,

syzkaller hit the following crash on
cf1fb158230edce8a0482bfb2e59b9c390477fb6
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


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Reported-by: syzbot+315fa6...@syzkaller.appspotmail.com
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audit: type=1400 audit(1515595879.379:7): avc: denied { map } for
pid=3498 comm="syzkaller002174" path="/root/syzkaller002174137" dev="sda1"
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
tc_ctl_action: received NO action attribs
WARNING: CPU: 0 PID: 3498 at net/netlink/af_netlink.c:2365
netlink_ack+0x625/0xa10 net/netlink/af_netlink.c:2363
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3498 Comm: syzkaller002174 Not tainted 4.15.0-rc7+ #256
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
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:1079
RIP: 0010:netlink_ack+0x625/0xa10 net/netlink/af_netlink.c:2363
RSP: 0018:ffff8801bfd8f790 EFLAGS: 00010293
RAX: ffff8801c00560c0 RBX: ffff8801d404dc00 RCX: ffffffff8455ad75
RDX: 0000000000000000 RSI: ffff8801c03a3530 RDI: ffff8801d404dcd8
RBP: ffff8801bfd8f848 R08: ffffed0038e8f55d R09: ffffed0038e8f55d
R10: 0000000000000003 R11: ffffed0038e8f55c R12: ffff8801c03a3500
R13: ffff8801c747aac0 R14: ffff8801d404d980 R15: 1ffff10037fb1ef8
netlink_rcv_skb+0x375/0x470 net/netlink/af_netlink.c:2414
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4423
netlink_unicast_kernel net/netlink/af_netlink.c:1275 [inline]
netlink_unicast+0x4ee/0x700 net/netlink/af_netlink.c:1301
netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1864
sock_sendmsg_nosec net/socket.c:636 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:646
___sys_sendmsg+0x767/0x8b0 net/socket.c:2026
__sys_sendmsg+0xe5/0x210 net/socket.c:2060
SYSC_sendmsg net/socket.c:2071 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2067
entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x440c39
RSP: 002b:00007ffeab2f1f98 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440c39
RDX: 0000000000008800 RSI: 00000000201dcfc8 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000217 R12: 00000000004025a0
R13: 0000000000402630 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Xin Long]

shoudn't the extack be cleared after the ack for one msg ?

@@ -2443,8 +2457,10 @@ int netlink_rcv_skb(struct sk_buff *skb, int
(*cb)(struct sk_buff *,
goto skip;

ack:
- if (nlh->nlmsg_flags & NLM_F_ACK || err)
+ if (nlh->nlmsg_flags & NLM_F_ACK || err) {
netlink_ack(skb, nlh, err, &extack);
+ memset(&extack, 0, sizeof(extack));
+ }

or just move the extack definition into the loop:

@@ -2417,11 +2431,11 @@ int netlink_rcv_skb(struct sk_buff *skb, int
(*cb)(struct sk_buff *,
struct nlmsghdr *,
struct netlink_ext_ack *))
{
- struct netlink_ext_ack extack = {};
struct nlmsghdr *nlh;
int err;

while (skb->len >= nlmsg_total_size(0)) {
+ struct netlink_ext_ack extack = {};
int msglen;

[David Ahern]

On 1/12/18 4:34 AM, Xin Long wrote:
>> audit: type=1400 audit(1515595879.379:7): avc: denied { map } for
>> pid=3498 comm="syzkaller002174" path="/root/syzkaller002174137" dev="sda1"
>> ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
>> tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
>> tc_ctl_action: received NO action attribs
>> WARNING: CPU: 0 PID: 3498 at net/netlink/af_netlink.c:2365
>> netlink_ack+0x625/0xa10 net/netlink/af_netlink.c:2363
>> Kernel panic - not syncing: panic_on_warn set ...
>
> shoudn't the extack be cleared after the ack for one msg ?
>

I sent a patch 2 days ago to do that; waiting for Dave to pick it up.