Subject: Re: [syzbot] [net?] BUG: unable to handle kernel paging request in nsim_bpf

From: Stanislav Fomichev <[email-masked]>
Date: Thu, 9 Nov 2023 16:21:09 -0800

On 11/08, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:

Looks like we need to have a distinction between dev-bound vs
dev-offloaded. I'll try to poke it.

> HEAD commit:    8de1e7afcc1c Merge branch 'for-next/core' into for-kernelci
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=158c647b680000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3e6feaeda5dcbc27
> dashboard link: https://syzkaller.appspot.com/bug?extid=44c2416196b7c607f226
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=104da6eb680000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14df3787680000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/0f00907f9764/disk-8de1e7af.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/0502fe78c60d/vmlinux-8de1e7af.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/192135168cc0/Image-8de1e7af.gz.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email-masked]
> 
> netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
> Unable to handle kernel paging request at virtual address dfff800000000003
> KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> Mem abort info:
>   ESR = 0x0000000096000005
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x05: level 1 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
>   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
>   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> [dfff800000000003] address between user and kernel address ranges
> Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 6085 Comm: syz-executor153 Not tainted 6.6.0-rc7-syzkaller-g8de1e7afcc1c #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : nsim_setup_prog_hw_checks drivers/net/netdevsim/bpf.c:320 [inline]
> pc : nsim_bpf+0x1e0/0xae0 drivers/net/netdevsim/bpf.c:562
> lr : nsim_bpf+0x8c/0xae0 drivers/net/netdevsim/bpf.c:554
> sp : ffff800096c67790
> x29: ffff800096c677a0 x28: dfff800000000000 x27: ffff700012d8cf00
> x26: dfff800000000000 x25: ffff800096c67a00 x24: 0000000000000008
> x23: ffff800096c67820 x22: 0000000000000018 x21: ffff800096c67820
> x20: ffff0000d3834cc0 x19: ffff0000d3834000 x18: ffff800096c67580
> x17: ffff8000805c1258 x16: ffff80008030c738 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000003
> x11: ffff0000d4ab3780 x10: 00000000000000bc x9 : ffff800085ce8bf0
> x8 : 0000000000000003 x7 : 0000000000000000 x6 : 0000000000000000
> x5 : ffff800092dee000 x4 : 0000000000000000 x3 : ffff80008030c754
> x2 : 0000000000000000 x1 : ffff80009001ef50 x0 : 0000000000000001
> Call trace:
>  nsim_setup_prog_hw_checks drivers/net/netdevsim/bpf.c:320 [inline]
>  nsim_bpf+0x1e0/0xae0 drivers/net/netdevsim/bpf.c:562
>  dev_xdp_install+0x124/0x2f0 net/core/dev.c:9199
>  dev_xdp_attach+0xa4c/0xcc8 net/core/dev.c:9351
>  dev_xdp_attach_link net/core/dev.c:9370 [inline]
>  bpf_xdp_link_attach+0x300/0x710 net/core/dev.c:9540
>  link_create+0x2c0/0x68c kernel/bpf/syscall.c:4954
>  __sys_bpf+0x4d4/0x5dc kernel/bpf/syscall.c:5414
>  __do_sys_bpf kernel/bpf/syscall.c:5448 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5446 [inline]
>  __arm64_sys_bpf+0x80/0x98 kernel/bpf/syscall.c:5446
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> Code: 96b3720d f94002c8 91006116 d343fec8 (387a6908) 
> ---[ end trace 0000000000000000 ]---
> ----------------
> Code disassembly (best guess):
>    0:	96b3720d 	bl	0xfffffffffacdc834
>    4:	f94002c8 	ldr	x8, [x22]
>    8:	91006116 	add	x22, x8, #0x18
>    c:	d343fec8 	lsr	x8, x22, #3
> * 10:	387a6908 	ldrb	w8, [x8, x26] <-- trapping instruction
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email-masked].
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> 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.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup