Re: [syzbot] [bpf?] [net?] general protection fault in __cpu_map_flush

[Toke Høiland-Jørgensen]

Hi Sebastian

The syzbot splat below shows up in recent -next kernels which
sorta-kinda wags its finger suggestively at the bpf_net_ctx_get()
changes. There's one for __dev_flush() as well:
https://lore.kernel.org/r/0000000000009d1d0a061d91b803@xxxxxxxxxx

Care to take a look? :)

Thanks!

-Toke


syzbot <syzbot+c226757eb784a9da3e8b@xxxxxxxxxxxxxxxxxxxxxxxxx> writes:

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    9ec6ec93f2c1 Add linux-next specific files for 20240724
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10e71ca1980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=83e9d0906fa0e2bd
> dashboard link: https://syzkaller.appspot.com/bug?extid=c226757eb784a9da3e8b
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17c0f8e3980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=151b9919980000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/c0ab2da24b1f/disk-9ec6ec93.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/da6faf16185f/vmlinux-9ec6ec93.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/1ad900571155/bzImage-9ec6ec93.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c226757eb784a9da3e8b@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> Oops: general protection fault, probably for non-canonical address 0xe3fffb24002e6fe6: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: maybe wild-memory-access in range [0x1ffff92001737f30-0x1ffff92001737f37]
> CPU: 1 UID: 0 PID: 11878 Comm: syz-executor412 Not tainted 6.10.0-next-20240724-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
> RIP: 0010:__cpu_map_flush+0x42/0xd0
> Code: e8 13 8c d6 ff 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 4d 12 3e 00 49 8b 1e 4c 39 f3 74 77 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 2f 12 3e 00 4c 8b 23 48 8d 7b c0
> RSP: 0018:ffffc90000a18b10 EFLAGS: 00010202
> RAX: 03ffff24002e6fe6 RBX: 1ffff92001737f30 RCX: ffff888074dc8000
> RDX: 0000000080000101 RSI: 0000000000000010 RDI: ffffc9000b9bf800
> RBP: dffffc0000000000 R08: ffffffff896d3b5a R09: 1ffffffff1f5f375
> R10: dffffc0000000000 R11: fffffbfff1f5f376 R12: ffffc9000b9bf800
> R13: ffffc9000b9bf820 R14: ffffc9000b9bf800 R15: dffffc0000000000
> FS:  0000555592677380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fd44da640f0 CR3: 000000001ea68000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <IRQ>
>  xdp_do_check_flushed+0x136/0x240 net/core/filter.c:4304
>  __napi_poll+0xe4/0x490 net/core/dev.c:6774
>  napi_poll net/core/dev.c:6840 [inline]
>  net_rx_action+0x89b/0x1240 net/core/dev.c:6962
>  handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
>  __do_softirq kernel/softirq.c:588 [inline]
>  invoke_softirq kernel/softirq.c:428 [inline]
>  __irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
>  irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
>  common_interrupt+0xaa/0xd0 arch/x86/kernel/irq.c:278
>  </IRQ>
>  <TASK>
>  asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
> RIP: 0010:check_kcov_mode kernel/kcov.c:184 [inline]
> RIP: 0010:__sanitizer_cov_trace_pc+0x37/0x70 kernel/kcov.c:207
> Code: 40 d7 03 00 65 8b 15 10 0c 70 7e f7 c2 00 01 ff 00 74 11 f7 c2 00 01 00 00 74 35 83 b9 1c 16 00 00 00 74 2c 8b 91 f8 15 00 00 <83> fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 48 8d 7e 01 8b 89 fc
> RSP: 0018:ffffc9000b9bf8a0 EFLAGS: 00000246
> RAX: ffffffff81410dcc RBX: 0000000000000000 RCX: ffff888074dc8000
> RDX: 0000000000000000 RSI: ffffffff8b942412 RDI: ffffffff8b942328
> RBP: 1ffff92001737f30 R08: ffffffff81410c60 R09: ffffc9000b9bfa70
> R10: 0000000000000003 R11: ffffffff817f7030 R12: ffffffff90294810
> R13: dffffc0000000000 R14: 1ffff92001737f30 R15: ffffffff90d0fbd4
>  unwind_next_frame+0x67c/0x2a00 arch/x86/kernel/unwind_orc.c:495
>  arch_stack_walk+0x151/0x1b0 arch/x86/kernel/stacktrace.c:25
>  stack_trace_save+0x118/0x1d0 kernel/stacktrace.c:122
>  kasan_save_stack mm/kasan/common.c:47 [inline]
>  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
>  kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
>  poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
>  __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
>  kasan_slab_free include/linux/kasan.h:184 [inline]
>  slab_free_hook mm/slub.c:2252 [inline]
>  slab_free mm/slub.c:4473 [inline]
>  kmem_cache_free+0x145/0x350 mm/slub.c:4548
>  __dentry_kill+0x497/0x630 fs/dcache.c:629
>  dput+0x19f/0x2b0 fs/dcache.c:852
>  __fput+0x5f8/0x8a0 fs/file_table.c:430
>  __do_sys_close fs/open.c:1566 [inline]
>  __se_sys_close fs/open.c:1551 [inline]
>  __x64_sys_close+0x7f/0x110 fs/open.c:1551
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd44d9ed9c0
> Code: ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 80 3d e1 76 07 00 00 74 17 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c
> RSP: 002b:00007fff7a1e95b8 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
> RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007fd44d9ed9c0
> RDX: 0000000000000e80 RSI: 0000000020000100 RDI: 0000000000000004
> RBP: 00007fff7a1e9600 R08: 00007fff7a1e95e0 R09: 00007fff7a1e95e0
> R10: 00007fff7a1e95e0 R11: 0000000000000202 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__cpu_map_flush+0x42/0xd0
> Code: e8 13 8c d6 ff 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 4d 12 3e 00 49 8b 1e 4c 39 f3 74 77 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 2f 12 3e 00 4c 8b 23 48 8d 7b c0
> RSP: 0018:ffffc90000a18b10 EFLAGS: 00010202
> RAX: 03ffff24002e6fe6 RBX: 1ffff92001737f30 RCX: ffff888074dc8000
> RDX: 0000000080000101 RSI: 0000000000000010 RDI: ffffc9000b9bf800
> RBP: dffffc0000000000 R08: ffffffff896d3b5a R09: 1ffffffff1f5f375
> R10: dffffc0000000000 R11: fffffbfff1f5f376 R12: ffffc9000b9bf800
> R13: ffffc9000b9bf820 R14: ffffc9000b9bf800 R15: dffffc0000000000
> FS:  0000555592677380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fd44da640f0 CR3: 000000001ea68000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:	e8 13 8c d6 ff       	call   0xffd68c18
>    5:	4c 89 f0             	mov    %r14,%rax
>    8:	48 c1 e8 03          	shr    $0x3,%rax
>    c:	42 80 3c 38 00       	cmpb   $0x0,(%rax,%r15,1)
>   11:	74 08                	je     0x1b
>   13:	4c 89 f7             	mov    %r14,%rdi
>   16:	e8 4d 12 3e 00       	call   0x3e1268
>   1b:	49 8b 1e             	mov    (%r14),%rbx
>   1e:	4c 39 f3             	cmp    %r14,%rbx
>   21:	74 77                	je     0x9a
>   23:	48 89 d8             	mov    %rbx,%rax
>   26:	48 c1 e8 03          	shr    $0x3,%rax
> * 2a:	42 80 3c 38 00       	cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
>   2f:	74 08                	je     0x39
>   31:	48 89 df             	mov    %rbx,%rdi
>   34:	e8 2f 12 3e 00       	call   0x3e1268
>   39:	4c 8b 23             	mov    (%rbx),%r12
>   3c:	48 8d 7b c0          	lea    -0x40(%rbx),%rdi
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.