netdev - Re: [aarch64] pc : ftrace_set_filter_ip+0x24/0xa0 - lr : bpf_trampoline

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Date:   Thu, 28 Jul 2022 11:18:02 +0800
From:   Xu Kuohai <xukuohai@...weicloud.com>
To:     Bruno Goncalves <bgoncalv@...hat.com>
Cc:     CKI Project <cki-project@...hat.com>,
        Song Liu <songliubraving@...com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [aarch64] pc : ftrace_set_filter_ip+0x24/0xa0 - lr :
 bpf_trampoline_update.constprop.0+0x428/0x4a0

On 7/27/2022 6:40 PM, Bruno Goncalves wrote:
> Hello,
> 
> Recently we started to hit the following panic when testing the
> net-next tree on aarch64. The first commit that we hit this is
> "b3fce974d423".
> 
> [   44.517109] audit: type=1334 audit(1658859870.268:59): prog-id=19 op=LOAD
> [   44.622031] Unable to handle kernel NULL pointer dereference at
> virtual address 0000000000000010
> [   44.624321] Mem abort info:
> [   44.625049]   ESR = 0x0000000096000004
> [   44.625935]   EC = 0x25: DABT (current EL), IL = 32 bits
> [   44.627182]   SET = 0, FnV = 0
> [   44.627930]   EA = 0, S1PTW = 0
> [   44.628684]   FSC = 0x04: level 0 translation fault
> [   44.629788] Data abort info:
> [   44.630474]   ISV = 0, ISS = 0x00000004
> [   44.631362]   CM = 0, WnR = 0
> [   44.632041] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000100ab5000
> [   44.633494] [0000000000000010] pgd=0000000000000000, p4d=0000000000000000
> [   44.635202] Internal error: Oops: 96000004 [#1] SMP
> [   44.636452] Modules linked in: xfs crct10dif_ce ghash_ce virtio_blk
> virtio_console virtio_mmio qemu_fw_cfg
> [   44.638713] CPU: 2 PID: 1 Comm: systemd Not tainted 5.19.0-rc7 #1
> [   44.640164] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
> [   44.641799] pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   44.643404] pc : ftrace_set_filter_ip+0x24/0xa0
> [   44.644659] lr : bpf_trampoline_update.constprop.0+0x428/0x4a0
> [   44.646118] sp : ffff80000803b9f0
> [   44.646950] x29: ffff80000803b9f0 x28: ffff0b5d80364400 x27: ffff80000803bb48
> [   44.648721] x26: ffff8000085ad000 x25: ffff0b5d809d2400 x24: 0000000000000000
> [   44.650493] x23: 00000000ffffffed x22: ffff0b5dd7ea0900 x21: 0000000000000000
> [   44.652279] x20: 0000000000000000 x19: 0000000000000000 x18: ffffffffffffffff
> [   44.654067] x17: 0000000000000000 x16: 0000000000000000 x15: ffffffffffffffff
> [   44.655787] x14: ffff0b5d809d2498 x13: ffff0b5d809d2432 x12: 0000000005f5e100
> [   44.657535] x11: abcc77118461cefd x10: 000000000000005f x9 : ffffa7219cb5b190
> [   44.659254] x8 : ffffa7219c8e0000 x7 : 0000000000000000 x6 : ffffa7219db075e0
> [   44.661066] x5 : ffffa7219d3130e0 x4 : ffffa7219cab9da0 x3 : 0000000000000000
> [   44.662837] x2 : 0000000000000000 x1 : ffffa7219cb7a5c0 x0 : 0000000000000000
> [   44.664675] Call trace:
> [   44.665274]  ftrace_set_filter_ip+0x24/0xa0
> [   44.666327]  bpf_trampoline_update.constprop.0+0x428/0x4a0
> [   44.667696]  __bpf_trampoline_link_prog+0xcc/0x1c0
> [   44.668834]  bpf_trampoline_link_prog+0x40/0x64
> [   44.669919]  bpf_tracing_prog_attach+0x120/0x490
> [   44.671011]  link_create+0xe0/0x2b0
> [   44.671869]  __sys_bpf+0x484/0xd30
> [   44.672706]  __arm64_sys_bpf+0x30/0x40
> [   44.673678]  invoke_syscall+0x78/0x100
> [   44.674623]  el0_svc_common.constprop.0+0x4c/0xf4
> [   44.675783]  do_el0_svc+0x38/0x4c
> [   44.676624]  el0_svc+0x34/0x100
> [   44.677429]  el0t_64_sync_handler+0x11c/0x150
> [   44.678532]  el0t_64_sync+0x190/0x194
> [   44.679439] Code: 2a0203f4 f90013f5 2a0303f5 f9001fe1 (f9400800)
> [   44.680959] ---[ end trace 0000000000000000 ]---
> [   44.682111] Kernel panic - not syncing: Oops: Fatal exception
> [   44.683488] SMP: stopping secondary CPUs
> [   44.684551] Kernel Offset: 0x2721948e0000 from 0xffff800008000000
> [   44.686095] PHYS_OFFSET: 0xfffff4a380000000
> [   44.687144] CPU features: 0x010,00022811,19001080
> [   44.688308] Memory Limit: none
> [   44.689082] ---[ end Kernel panic - not syncing: Oops: Fatal exception ]---
> 
> more logs:
> https://s3.us-east-1.amazonaws.com/arr-cki-prod-datawarehouse-public/datawarehouse-public/2022/07/26/redhat:597047279/build_aarch64_redhat:597047279_aarch64/tests/1/results_0001/console.log/console.log
> 
> https://datawarehouse.cki-project.org/kcidb/tests/4529120
> 
> CKI issue tracker: https://datawarehouse.cki-project.org/issue/1434
> 

Hello,

It's caused by a NULL tr->fops passed to ftrace_set_filter_ip:

if (tr->func.ftrace_managed) {
         ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 0);
         ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
}

Could you test it with the following patch?

--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -255,8 +255,15 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
                 return -ENOENT;

         if (tr->func.ftrace_managed) {
-               ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 0);
-               ret = register_ftrace_direct_multi(tr->fops,(long)new_addr);
+               if (tr->fops)
+                       ret = ftrace_set_filter_ip(tr->fops, (unsigned long)ip,
+                                                  0, 0);
+               else
+                       ret = -ENOTSUPP;
+
+               if (!ret)
+                       ret = register_ftrace_direct_multi(tr->fops,
+                                                          (long)new_addr);
         } else {
                 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
         }

Thanks.

> Thanks,
> Bruno Goncalves
> 
> .