Re: POWER9 crash due to STRICT_KERNEL_RWX (WAS: Re: Linux-next POWER9 NULL pointer NIP...)
From: Steven Rostedt
Date: Thu Apr 16 2020 - 22:17:58 EST
On Thu, 16 Apr 2020 21:19:10 -0400
Qian Cai <cai@xxxxxx> wrote:
> OK, reverted the commit,
>
> c55d7b5e6426 (âpowerpc: Remove STRICT_KERNEL_RWX incompatibility with RELOCATABLEâ)
>
> or set STRICT_KERNEL_RWX=n fixed the crash below and also mentioned in this thread,
This may be a symptom and not a cure.
>
> https://lore.kernel.org/lkml/15AC5B0E-A221-4B8C-9039-FA96B8EF7C88@xxxxxx/
>
> [ 148.110969][T13115] LTP: starting chown04_16
> [ 148.255048][T13380] kernel tried to execute exec-protected page (c0000000016804ac) - exploit attempt? (uid: 0)
> [ 148.255099][T13380] BUG: Unable to handle kernel instruction fetch
> [ 148.255122][T13380] Faulting instruction address: 0xc0000000016804ac
> [ 148.255136][T13380] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 148.255157][T13380] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=256 DEBUG_PAGEALLOC NUMA PowerNV
> [ 148.255171][T13380] Modules linked in: loop kvm_hv kvm xfs sd_mod bnx2x mdio ahci tg3 libahci libphy libata firmware_class dm_mirror dm_region_hash dm_log dm_mod
> [ 148.255213][T13380] CPU: 45 PID: 13380 Comm: chown04_16 Tainted: G W 5.6.0+ #7
> [ 148.255236][T13380] NIP: c0000000016804ac LR: c00800000fa60408 CTR: c0000000016804ac
> [ 148.255250][T13380] REGS: c0000010a6fafa00 TRAP: 0400 Tainted: G W (5.6.0+)
> [ 148.255281][T13380] MSR: 9000000010009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 84000248 XER: 20040000
> [ 148.255310][T13380] CFAR: c00800000fa66534 IRQMASK: 0
> [ 148.255310][T13380] GPR00: c000000000973268 c0000010a6fafc90 c000000001648200 0000000000000000
> [ 148.255310][T13380] GPR04: c000000d8a22dc00 c0000010a6fafd30 00000000b5e98331 ffffffff00012c9f
> [ 148.255310][T13380] GPR08: c000000d8a22dc00 0000000000000000 0000000000000000 c00000000163c520
> [ 148.255310][T13380] GPR12: c0000000016804ac c000001ffffdad80 0000000000000000 0000000000000000
> [ 148.255310][T13380] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [ 148.255310][T13380] GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [ 148.255310][T13380] GPR24: 00007fff8f5e2e48 0000000000000000 c00800000fa6a488 c0000010a6fafd30
> [ 148.255310][T13380] GPR28: 0000000000000000 000000007fffffff c00800000fa60400 c000000efd0c6780
> [ 148.255494][T13380] NIP [c0000000016804ac] sysctl_net_busy_read+0x0/0x4
The instruction pointer is on sysctl_net_busy_read? Isn't that data and
not code?
In net/socket.c:
#ifdef CONFIG_NET_RX_BUSY_POLL
unsigned int sysctl_net_busy_read __read_mostly;
unsigned int sysctl_net_busy_poll __read_mostly;
#endif
-- Steve
> [ 148.255516][T13380] LR [c00800000fa60408] find_free_cb+0x8/0x30 [loop]
> [ 148.255528][T13380] Call Trace:
> [ 148.255538][T13380] [c0000010a6fafc90] [c0000000009732c0] idr_for_each+0xf0/0x170 (unreliable)
> [ 148.255572][T13380] [c0000010a6fafd10] [c00800000fa626c4] loop_lookup.part.1+0x4c/0xb0 [loop]
> [ 148.255597][T13380] [c0000010a6fafd50] [c00800000fa634d8] loop_control_ioctl+0x120/0x1d0 [loop]
> [ 148.255623][T13380] [c0000010a6fafdb0] [c0000000004ddc08] ksys_ioctl+0xd8/0x130
> [ 148.255636][T13380] [c0000010a6fafe00] [c0000000004ddc88] sys_ioctl+0x28/0x40
> [ 148.255669][T13380] [c0000010a6fafe20] [c00000000000b378] system_call+0x5c/0x68
> [ 148.255699][T13380] Instruction dump:
> [ 148.255718][T13380] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> [ 148.255744][T13380] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> [ 148.255772][T13380] ---[ end trace a5894a74208c22ec ]---
> [ 148.576663][T13380]
> [ 149.576765][T13380] Kernel panic - not syncing: Fatal exception
>