[syzbot] general protection fault in dev_get_by_index_rcu (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 819d11507f66 bpf, selftests: Fix spelling mistake "tained"..
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=12500db3b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=22b66456935ee10
dashboard link: https://syzkaller.appspot.com/bug?extid=983941aa85af6ded1fd9
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=153a6cb3b00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=121c690bb00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+983941...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000003e: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000001f0-0x00000000000001f7]
CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:dev_index_hash net/core/dev.c:222 [inline]
RIP: 0010:dev_get_by_index_rcu+0x28/0x140 net/core/dev.c:885
Code: 00 00 41 55 41 54 55 89 f5 53 48 89 fb e8 00 9d 4d fa 48 8d bb f0 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 fc 00 00 00 48 8b 93 f0 01 00 00 40 0f b6 c5 48
RSP: 0018:ffffc90000d97608 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000100
RDX: 000000000000003e RSI: ffffffff872a14d0 RDI: 00000000000001f0
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff873745ad R11: 000000000008808a R12: ffff88806a062100
R13: 0000000000000003 R14: ffff88806a062100 R15: ffffc90001116000
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555733a848 CR3: 000000001479e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
____bpf_clone_redirect net/core/filter.c:2410 [inline]
bpf_clone_redirect+0x91/0x420 net/core/filter.c:2401
bpf_prog_bebbfe2050753572+0x56/0xcc0
__bpf_prog_run include/linux/filter.h:626 [inline]
bpf_prog_run_xdp include/linux/filter.h:801 [inline]
veth_xdp_rcv_skb+0x64b/0x1b20 drivers/net/veth.c:775
veth_xdp_rcv+0x3ac/0x810 drivers/net/veth.c:881
veth_poll+0x134/0x850 drivers/net/veth.c:913
__napi_poll+0xaf/0x440 net/core/dev.c:7023
napi_poll net/core/dev.c:7090 [inline]
net_rx_action+0x801/0xb40 net/core/dev.c:7177
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558
run_ksoftirqd kernel/softirq.c:921 [inline]
run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913
smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Modules linked in:
---[ end trace 86b7d5782a67ad32 ]---
RIP: 0010:dev_index_hash net/core/dev.c:222 [inline]
RIP: 0010:dev_get_by_index_rcu+0x28/0x140 net/core/dev.c:885
Code: 00 00 41 55 41 54 55 89 f5 53 48 89 fb e8 00 9d 4d fa 48 8d bb f0 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 fc 00 00 00 48 8b 93 f0 01 00 00 40 0f b6 c5 48
RSP: 0018:ffffc90000d97608 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000100
RDX: 000000000000003e RSI: ffffffff872a14d0 RDI: 00000000000001f0
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff873745ad R11: 000000000008808a R12: ffff88806a062100
R13: 0000000000000003 R14: ffff88806a062100 R15: ffffc90001116000
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555733a848 CR3: 000000001479e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 41 55 push %r13
4: 41 54 push %r12
6: 55 push %rbp
7: 89 f5 mov %esi,%ebp
9: 53 push %rbx
a: 48 89 fb mov %rdi,%rbx
d: e8 00 9d 4d fa callq 0xfa4d9d12
12: 48 8d bb f0 01 00 00 lea 0x1f0(%rbx),%rdi
19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
20: fc ff df
23: 48 89 fa mov %rdi,%rdx
26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2e: 0f 85 fc 00 00 00 jne 0x130
34: 48 8b 93 f0 01 00 00 mov 0x1f0(%rbx),%rdx
3b: 40 0f b6 c5 movzbl %bpl,%eax
3f: 48 rex.W


---
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[Alexei Starovoitov]

Toke, Jesper,

please take a look.
Seems to be in your area of expertise.

Thanks

[Toke Høiland-Jørgensen]

Alexei Starovoitov <alexei.st...@gmail.com> writes:

> Toke, Jesper,
>
> please take a look.
> Seems to be in your area of expertise.

Yikes, I think I see the problem. Let me just confirm and I'll send a fix :)

-Toke

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+983941...@syzkaller.appspotmail.com

Tested on:

commit: e4a3d6a6 Merge branch '100GbE' of git://git.kernel.org..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
kernel config: https://syzkaller.appspot.com/x/.config?x=34274384f56cbb7e

dashboard link: https://syzkaller.appspot.com/bug?extid=983941aa85af6ded1fd9
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1692c003b00000

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

[Toke Høiland-Jørgensen]

Fix here: https://lore.kernel.org/r/20220107183049...@redhat.com

-Toke