[PATCH] powerpc/47x: Fix 47x syscall return crash

[Michael Ellerman]

On Tue, 10 Oct 2023 22:47:50 +1100, Michael Ellerman wrote:
> Eddie reported that newer kernels were crashing during boot on his 476
> FSP2 system:
> 
>   kernel tried to execute user page (b7ee2000) - exploit attempt? (uid: 0)
>   BUG: Unable to handle kernel instruction fetch
>   Faulting instruction address: 0xb7ee2000
>   Oops: Kernel access of bad area, sig: 11 [#1]
>   BE PAGE_SIZE=4K FSP-2
>   Modules linked in:
>   CPU: 0 PID: 61 Comm: mount Not tainted 6.1.55-d23900f.ppcnf-fsp2 #1
>   Hardware name: ibm,fsp2 476fpe 0x7ff520c0 FSP-2
>   NIP:  b7ee2000 LR: 8c008000 CTR: 00000000
>   REGS: bffebd83 TRAP: 0400   Not tainted (6.1.55-d23900f.ppcnf-fs p2)
>   MSR:  00000030 <IR,DR>  CR: 00001000  XER: 20000000
>   GPR00: c00110ac bffebe63 bffebe7e bffebe88 8c008000 00001000 00000d12 b7ee2000
>   GPR08: 00000033 00000000 00000000 c139df10 48224824 1016c314 10160000 00000000
>   GPR16: 10160000 10160000 00000008 00000000 10160000 00000000 10160000 1017f5b0
>   GPR24: 1017fa50 1017f4f0 1017fa50 1017f740 1017f630 00000000 00000000 1017f4f0
>   NIP [b7ee2000] 0xb7ee2000
>   LR [8c008000] 0x8c008000
>   Call Trace:
>   Instruction dump:
>   XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>   XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>   ---[ end trace 0000000000000000 ]---
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/47x: Fix 47x syscall return crash
      https://git.kernel.org/powerpc/c/f0eee815babed70a749d2496a7678be5b45b4c14

cheers