WARNING in bpf_warn_invalid_xdp_action

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d0f41851 net, ip_tunnel: fix namespaces move
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=10e94d85e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=8ce4113dadc4789fac74
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f99369e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d85601e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8ce411...@syzkaller.appspotmail.com

------------[ cut here ]------------
Illegal XDP return value 4294967274, expect packet loss!
WARNING: CPU: 0 PID: 9780 at net/core/filter.c:6918 bpf_warn_invalid_xdp_action net/core/filter.c:6918 [inline]
WARNING: CPU: 0 PID: 9780 at net/core/filter.c:6918 bpf_warn_invalid_xdp_action+0x77/0x90 net/core/filter.c:6914
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 9780 Comm: syz-executor429 Not tainted 5.5.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x3e kernel/panic.c:582
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
fixup_bug arch/x86/kernel/traps.c:169 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:bpf_warn_invalid_xdp_action net/core/filter.c:6918 [inline]
RIP: 0010:bpf_warn_invalid_xdp_action+0x77/0x90 net/core/filter.c:6914
Code: 00 f9 d6 88 41 83 fc 04 48 c7 c6 40 f9 d6 88 4c 0f 46 ee e8 2b 9e 49 fb 44 89 e2 48 c7 c7 80 f9 d6 88 4c 89 ee e8 18 4e 1a fb <0f> 0b e8 12 9e 49 fb 5b 41 5c 41 5d 5d c3 90 66 2e 0f 1f 84 00 00
RSP: 0018:ffffc900000079a8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000100 RSI: ffffffff815e5326 RDI: fffff52000000f27
RBP: ffffc900000079c0 R08: ffff88809ff963c0 R09: ffffed1015d045c9
R10: ffffed1015d045c8 R11: ffff8880ae822e43 R12: 00000000ffffffea
R13: ffffffff88d6f900 R14: ffff8880927ea110 R15: ffff88809e257180
netif_receive_generic_xdp net/core/dev.c:4564 [inline]
do_xdp_generic.part.0+0xebb/0x1790 net/core/dev.c:4613
do_xdp_generic net/core/dev.c:4985 [inline]
__netif_receive_skb_core+0x68b/0x30b0 net/core/dev.c:4985
__netif_receive_skb_one_core+0xa8/0x1a0 net/core/dev.c:5148
__netif_receive_skb+0x2c/0x1d0 net/core/dev.c:5264
process_backlog+0x206/0x750 net/core/dev.c:6095
napi_poll net/core/dev.c:6532 [inline]
net_rx_action+0x508/0x1120 net/core/dev.c:6600
__do_softirq+0x262/0x98c kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x19b/0x1e0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1a3/0x610 arch/x86/kernel/apic/apic.c:1137
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:console_unlock+0xbb8/0xf00 kernel/printk/printk.c:2481
Code: 93 89 48 c1 e8 03 42 80 3c 30 00 0f 85 e4 02 00 00 48 83 3d c1 43 35 08 00 0f 84 91 01 00 00 e8 3e 05 17 00 48 8b 7d 98 57 9d <0f> 1f 44 00 00 e9 6d ff ff ff e8 29 05 17 00 48 8b 7d 08 c7 05 1b
RSP: 0018:ffffc90001f26b38 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
RAX: ffff88809ff963c0 RBX: 0000000000000200 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffffffff815defe2 RDI: 0000000000000293
RBP: ffffc90001f26bc0 R08: 1ffffffff165e79c R09: fffffbfff165e79d
R10: fffffbfff165e79c R11: ffffffff8b2f3ce7 R12: 0000000000000000
R13: ffffffff84b35860 R14: dffffc0000000000 R15: ffffffff8a0fc990
vprintk_emit+0x2a0/0x700 kernel/printk/printk.c:1996
vprintk_default+0x28/0x30 kernel/printk/printk.c:2023
vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386
printk+0xba/0xed kernel/printk/printk.c:2056
validate_nla lib/nlattr.c:178 [inline]
__nla_validate_parse.cold+0x4d/0x60 lib/nlattr.c:381
__nla_parse+0x43/0x60 lib/nlattr.c:478
nla_parse_nested_deprecated include/net/netlink.h:1166 [inline]
do_setlink+0x2ca2/0x3720 net/core/rtnetlink.c:2773
rtnl_group_changelink net/core/rtnetlink.c:3089 [inline]
__rtnl_newlink+0xdd2/0x1790 net/core/rtnetlink.c:3243
rtnl_newlink+0x69/0xa0 net/core/rtnetlink.c:3363
rtnetlink_rcv_msg+0x45e/0xaf0 net/core/rtnetlink.c:5424
netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5442
netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
netlink_unicast+0x58c/0x7d0 net/netlink/af_netlink.c:1328
netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:639 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:659
____sys_sendmsg+0x753/0x880 net/socket.c:2330
___sys_sendmsg+0x100/0x170 net/socket.c:2384
__sys_sendmsg+0x105/0x1d0 net/socket.c:2417
__do_sys_sendmsg net/socket.c:2426 [inline]
__se_sys_sendmsg net/socket.c:2424 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2424
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x442af9
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 7b 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd3ded00a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000442af9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 00007ffd3ded00c0 R08: 0000000001bbbbbb R09: 0000000001bbbbbb
R10: 0000000001bbbbbb R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000404090 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
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syzbot can test patches for this bug, for details see:
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[syzbot]

syzbot has bisected this bug to:

commit 58956317c8de52009d1a38a721474c24aef74fe7
Author: David Ahern <dsa...@gmail.com>
Date: Fri Dec 7 20:24:57 2018 +0000

neighbor: Improve garbage collection

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=124a5985e00000
start commit: d0f41851 net, ip_tunnel: fix namespaces move
git tree: net
final crash: https://syzkaller.appspot.com/x/report.txt?x=114a5985e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=164a5985e00000

kernel config: https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=8ce4113dadc4789fac74

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f99369e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d85601e00000

Reported-by: syzbot+8ce411...@syzkaller.appspotmail.com
Fixes: 58956317c8de ("neighbor: Improve garbage collection")

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

[Eric Dumazet]

bisection looks bogus...

It would be nice to have alternative helpers to conveniently replace some WARN_ON/WARN_ONCE/...
and not having to hand-code stuff like :

diff --git a/net/core/filter.c b/net/core/filter.c
index 538f6a735a19f017df8e10149cb578107ddc8cbb..633988f7c81b3b4f015d827ccb485e8b227ad20b 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6913,11 +6913,15 @@ static bool xdp_is_valid_access(int off, int size,

void bpf_warn_invalid_xdp_action(u32 act)
{
+ static bool __section(.data.once) warned;
const u32 act_max = XDP_REDIRECT;

- WARN_ONCE(1, "%s XDP return value %u, expect packet loss!\n",
- act > act_max ? "Illegal" : "Driver unsupported",
- act);
+ if (!warned) {
+ warned = true;
+ pr_err("%s XDP return value %u, expect packet loss!\n",
+ act > act_max ? "Illegal" : "Driver unsupported", act);
+ dump_stack();
+ }
}
EXPORT_SYMBOL_GPL(bpf_warn_invalid_xdp_action);

[Dmitry Vyukov]

If a single caller of this function would be enough (or maybe grand
caller with a macro), then we could use pr_err_once/ratelimited and
print 1 line with error and caller function.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 2cbad989033bff0256675c38f96f5faab852af4b
Author: Paolo Abeni <pab...@redhat.com>
Date: Tue Nov 30 10:08:06 2021 +0000

bpf: Do not WARN in bpf_warn_invalid_xdp_action()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10d50baa700000
start commit: b3c8e0de473e Merge branch '40GbE' of git://git.kernel.org/..
git tree: net
kernel config: https://syzkaller.appspot.com/x/.config?x=1a86c22260afac2f
dashboard link: https://syzkaller.appspot.com/bug?extid=8ce4113dadc4789fac74
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=113c8a3bb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16eb4307b00000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: bpf: Do not WARN in bpf_warn_invalid_xdp_action()

[Dmitry Vyukov]

Looks legit: