linux.git/arch, branch v6.3-rc5 Linux kernel source tree Merge tag 'powerpc-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux 2023-04-02T17:01:56+00:00 Linus Torvalds torvalds@linux-foundation.org 2023-04-02T17:01:56+00:00 95d0b9d89d78e0983d4feb012b0f12d13d1ae19a Pull powerpc fixes from Michael Ellerman: - Fix a false positive warning in __pte_needs_flush() (with DEBUG_VM=y) - Fix oops when a PF_IO_WORKER thread tries to core dump - Don't try to reconfigure VAS when it's disabled Thanks to Benjamin Gray, Haren Myneni, Jens Axboe, Nathan Lynch, and Russell Currey. * tag 'powerpc-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: powerpc/pseries/vas: Ignore VAS update for DLPAR if copy/paste is not enabled powerpc: Don't try to copy PPR for task with NULL pt_regs powerpc/64s: Fix __pte_needs_flush() false positive warning 
Pull powerpc fixes from Michael Ellerman:

 - Fix a false positive warning in __pte_needs_flush() (with DEBUG_VM=y)

 - Fix oops when a PF_IO_WORKER thread tries to core dump

 - Don't try to reconfigure VAS when it's disabled

Thanks to Benjamin Gray, Haren Myneni, Jens Axboe, Nathan Lynch, and
Russell Currey.

* tag 'powerpc-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/pseries/vas: Ignore VAS update for DLPAR if copy/paste is not enabled
  powerpc: Don't try to copy PPR for task with NULL pt_regs
  powerpc/64s: Fix __pte_needs_flush() false positive warning
Merge tag 'riscv-for-linus-6.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux 2023-03-31T17:15:17+00:00 Linus Torvalds torvalds@linux-foundation.org 2023-03-31T17:15:17+00:00 39f692125c388aa657e77e5ae07ea72be02d99a5 Pull RISC-V fixes from Palmer Dabbelt: - A fix for FPU probing in XIP kernels - Always enable the alternative framework for non-XIP kernels * tag 'riscv-for-linus-6.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely() 
Pull RISC-V fixes from Palmer Dabbelt:

 - A fix for FPU probing in XIP kernels

 - Always enable the alternative framework for non-XIP kernels

* tag 'riscv-for-linus-6.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels
  RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely()
Merge tag 'mips-fixes_6.3_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux 2023-03-31T17:12:07+00:00 Linus Torvalds torvalds@linux-foundation.org 2023-03-31T17:12:07+00:00 52f1959502dec5069dcd247ce0462cdc608494b1 Pull MIPS fix from Thomas Bogendoerfer: "Fix to avoid crash on BCM6358 platforms" * tag 'mips-fixes_6.3_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: mips: bmips: BCM6358: disable RAC flush for TP1 
Pull MIPS fix from Thomas Bogendoerfer:
 "Fix to avoid crash on BCM6358 platforms"

* tag 'mips-fixes_6.3_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  mips: bmips: BCM6358: disable RAC flush for TP1
Merge patch series "RISC-V: Fixes for riscv_has_extension[un]likely()'s alternative dependency" 2023-03-29T19:23:00+00:00 Palmer Dabbelt palmer@rivosinc.com 2023-03-29T18:48:41+00:00 4622f159098e098611f393cccf73d52b007e70bc Conor Dooley <conor.dooley@microchip.com> says: Here's my attempt at fixing both the use of an FPU on XIP kernels and the issue that Jason ran into where CONFIG_FPU, which needs the alternatives frame work for has_fpu() checks, could be enabled without the alternatives actually being present. For the former, a "slow" fallback that does not use alternatives is added to riscv_has_extension_[un]likely() that can be used with XIP. Obviously, we want to make use of Jisheng's alternatives based approach where possible, so any users of riscv_has_extension_[un]likely() will want to make sure that they select RISCV_ALTERNATIVE. If they don't however, they'll hit the fallback path which (should, sparing a silly mistake from me!) behave in the same way, thus succeeding silently. Sounds like a To prevent "depends on !XIP_KERNEL; select RISCV_ALTERNATIVE" spreading like the plague through the various places that want to check for the presence of extensions, and sidestep the potential silent "success" mentioned above, all users RISCV_ALTERNATIVE are converted from selects to dependencies, with the option being selected for all !XIP_KERNEL builds. I know that the VDSO was a key place that Jisheng wanted to use the new helper rather than static branches, and I think the fallback path should not cause issues there. See the thread at [1] for the prior discussion. 1 - https://lore.kernel.org/linux-riscv/20230128172856.3814-1-jszhang@kernel.org/T/#m21390d570997145d31dd8bb95002fd61f99c6573 [Palmer: merging in the fixes as a branch as there's some features that depend on it.] * b4-shazam-merge: RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely() Link: https://lore.kernel.org/r/20230324100538.3514663-1-conor.dooley@microchip.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> 
Conor Dooley <conor.dooley@microchip.com> says:

Here's my attempt at fixing both the use of an FPU on XIP kernels and
the issue that Jason ran into where CONFIG_FPU, which needs the
alternatives frame work for has_fpu() checks, could be enabled without
the alternatives actually being present.

For the former, a "slow" fallback that does not use alternatives is
added to riscv_has_extension_[un]likely() that can be used with XIP.
Obviously, we want to make use of Jisheng's alternatives based approach
where possible, so any users of riscv_has_extension_[un]likely() will
want to make sure that they select RISCV_ALTERNATIVE.
If they don't however, they'll hit the fallback path which (should,
sparing a silly mistake from me!) behave in the same way, thus
succeeding silently. Sounds like a

To prevent "depends on !XIP_KERNEL; select RISCV_ALTERNATIVE" spreading
like the plague through the various places that want to check for the
presence of extensions, and sidestep the potential silent "success"
mentioned above, all users RISCV_ALTERNATIVE are converted from selects
to dependencies, with the option being selected for all !XIP_KERNEL
builds.

I know that the VDSO was a key place that Jisheng wanted to use the new
helper rather than static branches, and I think the fallback path
should not cause issues there.

See the thread at [1] for the prior discussion.

1 - https://lore.kernel.org/linux-riscv/20230128172856.3814-1-jszhang@kernel.org/T/#m21390d570997145d31dd8bb95002fd61f99c6573

[Palmer: merging in the fixes as a branch as there's some features that
depend on it.]

* b4-shazam-merge:
  RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels
  RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely()

Link: https://lore.kernel.org/r/20230324100538.3514663-1-conor.dooley@microchip.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels 2023-03-29T18:48:39+00:00 Conor Dooley conor.dooley@microchip.com 2023-03-24T10:05:39+00:00 1ee7fc3f4d0a93831a20d5566f203d5ad6d44de8 When moving switch_to's has_fpu() over to using riscv_has_extension_likely() rather than static branches, the FPU code gained a dependency on the alternatives framework. That dependency has now been removed, as riscv_has_extension_ikely() now contains a fallback path, using __riscv_isa_extension_available(), but if CONFIG_RISCV_ALTERNATIVE isn't selected when CONFIG_FPU is, has_fpu() checks will not benefit from the "fast path" that the alternatives framework provides. We want to ensure that alternatives are available whenever riscv_has_extension_[un]likely() is used, rather than silently falling back to the slow path, but rather than rely on selecting RISCV_ALTERNATIVE in the myriad of locations that may use riscv_has_extension_[un]likely(), select it (almost) always instead by adding it to the main RISCV config entry. xip kernels cannot make use of the alternatives framework, so it is not enabled for those configurations, although this is the status quo. All current sites that select RISCV_ALTERNATIVE are converted to dependencies on the option instead. The explicit dependencies on !XIP_KERNEL can be dropped, as RISCV_ALTERNATIVE is not user selectable. Fixes: 702e64550b12 ("riscv: fpu: switch has_fpu() to riscv_has_extension_likely()") Link: https://lore.kernel.org/all/ZBruFRwt3rUVngPu@zx2c4.com/ Reported-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Conor Dooley <conor.dooley@microchip.com> Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com> Link: https://lore.kernel.org/r/20230324100538.3514663-3-conor.dooley@microchip.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> 
When moving switch_to's has_fpu() over to using
riscv_has_extension_likely() rather than static branches, the FPU code
gained a dependency on the alternatives framework.
That dependency has now been removed, as riscv_has_extension_ikely() now
contains a fallback path, using __riscv_isa_extension_available(), but
if CONFIG_RISCV_ALTERNATIVE isn't selected when CONFIG_FPU is, has_fpu()
checks will not benefit from the "fast path" that the alternatives
framework provides.

We want to ensure that alternatives are available whenever
riscv_has_extension_[un]likely() is used, rather than silently falling
back to the slow path, but rather than rely on selecting
RISCV_ALTERNATIVE in the myriad of locations that may use
riscv_has_extension_[un]likely(), select it (almost) always instead by
adding it to the main RISCV config entry.
xip kernels cannot make use of the alternatives framework, so it is not
enabled for those configurations, although this is the status quo.

All current sites that select RISCV_ALTERNATIVE are converted to
dependencies on the option instead. The explicit dependencies on
!XIP_KERNEL can be dropped, as RISCV_ALTERNATIVE is not user selectable.

Fixes: 702e64550b12 ("riscv: fpu: switch has_fpu() to riscv_has_extension_likely()")
Link: https://lore.kernel.org/all/ZBruFRwt3rUVngPu@zx2c4.com/
Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20230324100538.3514663-3-conor.dooley@microchip.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely() 2023-03-29T18:48:38+00:00 Conor Dooley conor.dooley@microchip.com 2023-03-24T10:05:38+00:00 1aa866931b8026a0dd636e9ef7b5c5dfb4cc5ce8 The has_fpu() check, which in turn calls riscv_has_extension_likely(), relies on alternatives to figure out whether the system has an FPU. As a result, it will malfunction on XIP kernels, as they do not support the alternatives mechanism. When alternatives support is not present, fall back to using __riscv_isa_extension_available() in riscv_has_extension_[un]likely() instead stead, which handily takes the same argument, so that kernels that do not support alternatives can accurately report the presence of FPU support. Fixes: 702e64550b12 ("riscv: fpu: switch has_fpu() to riscv_has_extension_likely()") Link: https://lore.kernel.org/all/ad445951-3d13-4644-94d9-e0989cda39c3@spud/ Signed-off-by: Conor Dooley <conor.dooley@microchip.com> Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com> Link: https://lore.kernel.org/r/20230324100538.3514663-2-conor.dooley@microchip.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> 
The has_fpu() check, which in turn calls riscv_has_extension_likely(),
relies on alternatives to figure out whether the system has an FPU.
As a result, it will malfunction on XIP kernels, as they do not support
the alternatives mechanism.

When alternatives support is not present, fall back to using
__riscv_isa_extension_available() in riscv_has_extension_[un]likely()
instead stead, which handily takes the same argument, so that kernels
that do not support alternatives can accurately report the presence of
FPU support.

Fixes: 702e64550b12 ("riscv: fpu: switch has_fpu() to riscv_has_extension_likely()")
Link: https://lore.kernel.org/all/ad445951-3d13-4644-94d9-e0989cda39c3@spud/
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20230324100538.3514663-2-conor.dooley@microchip.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Merge tag 'xtensa-20230327' of https://github.com/jcmvbkbc/linux-xtensa 2023-03-29T17:24:07+00:00 Linus Torvalds torvalds@linux-foundation.org 2023-03-29T17:24:07+00:00 ffe78bbd512166e0ef1cc4858010b128c510ed7d Pull xtensa fixes from Max Filippov: - fix KASAN report in show_stack - drop linux-xtensa mailing list from the MAINTAINERS file * tag 'xtensa-20230327' of https://github.com/jcmvbkbc/linux-xtensa: MAINTAINERS: xtensa: drop linux-xtensa@linux-xtensa.org mailing list xtensa: fix KASAN report for show_stack 
Pull xtensa fixes from Max Filippov:

 - fix KASAN report in show_stack

 - drop linux-xtensa mailing list from the MAINTAINERS file

* tag 'xtensa-20230327' of https://github.com/jcmvbkbc/linux-xtensa:
  MAINTAINERS: xtensa: drop linux-xtensa@linux-xtensa.org mailing list
  xtensa: fix KASAN report for show_stack
powerpc/pseries/vas: Ignore VAS update for DLPAR if copy/paste is not enabled 2023-03-29T12:01:35+00:00 Haren Myneni haren@linux.ibm.com 2023-03-21T02:50:08+00:00 eca9f6e6f83b6725b84e1c76fdde19b003cff0eb The hypervisor supports user-mode NX from Power10. pseries_vas_dlpar_cpu() is called from lparcfg_write() to update VAS windows for DLPAR event in shared processor mode and the kernel gets -ENOTSUPP for HCALLs if the user-mode NX is not supported. The current VAS implementation also supports only with Radix page tables. Whereas in dedicated processor mode, pseries_vas_notifier() is registered only if the copy/paste feature is enabled. So instead of displaying HCALL error messages, update VAS capabilities if the copy/paste feature is available. This patch ignores updating VAS capabilities in pseries_vas_dlpar_cpu() and returns success if the copy/paste feature is not enabled. Then lparcfg_write() completes the processor DLPAR operations without any failures. Fixes: 2147783d6bf0 ("powerpc/pseries: Use lparcfg to reconfig VAS windows for DLPAR CPU") Cc: stable@vger.kernel.org # v6.1+ Signed-off-by: Haren Myneni <haren@linux.ibm.com> Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/1d0e727e7dbd9a28627ef08ca9df9c86a50175e2.camel@linux.ibm.com 
The hypervisor supports user-mode NX from Power10.

pseries_vas_dlpar_cpu() is called from lparcfg_write() to update VAS
windows for DLPAR event in shared processor mode and the kernel gets
-ENOTSUPP for HCALLs if the user-mode NX is not supported. The current
VAS implementation also supports only with Radix page tables. Whereas in
dedicated processor mode, pseries_vas_notifier() is registered only if
the copy/paste feature is enabled. So instead of displaying HCALL error
messages, update VAS capabilities if the copy/paste feature is
available.

This patch ignores updating VAS capabilities in pseries_vas_dlpar_cpu()
and returns success if the copy/paste feature is not enabled. Then
lparcfg_write() completes the processor DLPAR operations without any
failures.

Fixes: 2147783d6bf0 ("powerpc/pseries: Use lparcfg to reconfig VAS windows for DLPAR CPU")
Cc: stable@vger.kernel.org # v6.1+
Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/1d0e727e7dbd9a28627ef08ca9df9c86a50175e2.camel@linux.ibm.com
Merge tag 's390-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2023-03-28T17:43:04+00:00 Linus Torvalds torvalds@linux-foundation.org 2023-03-28T17:43:04+00:00 05c24161f4d2adc0deb6f3f0f55d25e12fbbdcde Pull s390 fixes from Vasily Gorbik: - Fix an error handling issue with PTRACE_GET_LAST_BREAK request so that -EFAULT is returned if put_user() fails, instead of ignoring it - Fix a build race for the modules_prepare target when CONFIG_EXPOLINE_EXTERN is enabled by reintroducing the dependence on scripts - Fix a memory leak in vfio_ap device driver - Add missing earlyclobber annotations to __clear_user() inline assembly to prevent incorrect register allocation * tag 's390-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: s390/ptrace: fix PTRACE_GET_LAST_BREAK error handling s390: reintroduce expoline dependence to scripts s390/vfio-ap: fix memory leak in vfio_ap device driver s390/uaccess: add missing earlyclobber annotations to __clear_user() 
Pull s390 fixes from Vasily Gorbik:

 - Fix an error handling issue with PTRACE_GET_LAST_BREAK request so
   that -EFAULT is returned if put_user() fails, instead of ignoring it

 - Fix a build race for the modules_prepare target when
   CONFIG_EXPOLINE_EXTERN is enabled by reintroducing the dependence on
   scripts

 - Fix a memory leak in vfio_ap device driver

 - Add missing earlyclobber annotations to __clear_user() inline
   assembly to prevent incorrect register allocation

* tag 's390-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/ptrace: fix PTRACE_GET_LAST_BREAK error handling
  s390: reintroduce expoline dependence to scripts
  s390/vfio-ap: fix memory leak in vfio_ap device driver
  s390/uaccess: add missing earlyclobber annotations to __clear_user()
powerpc: Don't try to copy PPR for task with NULL pt_regs 2023-03-28T11:11:41+00:00 Jens Axboe axboe@kernel.dk 2023-03-26T22:15:57+00:00 fd7276189450110ed835eb0a334e62d2f1c4e3be powerpc sets up PF_KTHREAD and PF_IO_WORKER with a NULL pt_regs, which from my (arguably very short) checking is not commonly done for other archs. This is fine, except when PF_IO_WORKER's have been created and the task does something that causes a coredump to be generated. Then we get this crash: Kernel attempted to read user page (160) - exploit attempt? (uid: 1000) BUG: Kernel NULL pointer dereference on read at 0x00000160 Faulting instruction address: 0xc0000000000c3a60 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=32 NUMA pSeries Modules linked in: bochs drm_vram_helper drm_kms_helper xts binfmt_misc ecb ctr syscopyarea sysfillrect cbc sysimgblt drm_ttm_helper aes_generic ttm sg libaes evdev joydev virtio_balloon vmx_crypto gf128mul drm dm_mod fuse loop configfs drm_panel_orientation_quirks ip_tables x_tables autofs4 hid_generic usbhid hid xhci_pci xhci_hcd usbcore usb_common sd_mod CPU: 1 PID: 1982 Comm: ppc-crash Not tainted 6.3.0-rc2+ #88 Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries NIP: c0000000000c3a60 LR: c000000000039944 CTR: c0000000000398e0 REGS: c0000000041833b0 TRAP: 0300 Not tainted (6.3.0-rc2+) MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 88082828 XER: 200400f8 ... NIP memcpy_power7+0x200/0x7d0 LR ppr_get+0x64/0xb0 Call Trace: ppr_get+0x40/0xb0 (unreliable) __regset_get+0x180/0x1f0 regset_get_alloc+0x64/0x90 elf_core_dump+0xb98/0x1b60 do_coredump+0x1c34/0x24a0 get_signal+0x71c/0x1410 do_notify_resume+0x140/0x6f0 interrupt_exit_user_prepare_main+0x29c/0x320 interrupt_exit_user_prepare+0x6c/0xa0 interrupt_return_srr_user+0x8/0x138 Because ppr_get() is trying to copy from a PF_IO_WORKER with a NULL pt_regs. Check for a valid pt_regs in both ppc_get/ppr_set, and return an error if not set. The actual error value doesn't seem to be important here, so just pick -EINVAL. Fixes: fa439810cc1b ("powerpc/ptrace: Enable support for NT_PPPC_TAR, NT_PPC_PPR, NT_PPC_DSCR") Cc: stable@vger.kernel.org # v4.8+ Signed-off-by: Jens Axboe <axboe@kernel.dk> [mpe: Trim oops in change log, add Fixes & Cc stable] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/d9f63344-fe7c-56ae-b420-4a1a04a2ae4c@kernel.dk 
powerpc sets up PF_KTHREAD and PF_IO_WORKER with a NULL pt_regs, which
from my (arguably very short) checking is not commonly done for other
archs. This is fine, except when PF_IO_WORKER's have been created and
the task does something that causes a coredump to be generated. Then we
get this crash:

  Kernel attempted to read user page (160) - exploit attempt? (uid: 1000)
  BUG: Kernel NULL pointer dereference on read at 0x00000160
  Faulting instruction address: 0xc0000000000c3a60
  Oops: Kernel access of bad area, sig: 11 [#1]
  LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=32 NUMA pSeries
  Modules linked in: bochs drm_vram_helper drm_kms_helper xts binfmt_misc ecb ctr syscopyarea sysfillrect cbc sysimgblt drm_ttm_helper aes_generic ttm sg libaes evdev joydev virtio_balloon vmx_crypto gf128mul drm dm_mod fuse loop configfs drm_panel_orientation_quirks ip_tables x_tables autofs4 hid_generic usbhid hid xhci_pci xhci_hcd usbcore usb_common sd_mod
  CPU: 1 PID: 1982 Comm: ppc-crash Not tainted 6.3.0-rc2+ #88
  Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries
  NIP:  c0000000000c3a60 LR: c000000000039944 CTR: c0000000000398e0
  REGS: c0000000041833b0 TRAP: 0300   Not tainted  (6.3.0-rc2+)
  MSR:  800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 88082828  XER: 200400f8
  ...
  NIP memcpy_power7+0x200/0x7d0
  LR  ppr_get+0x64/0xb0
  Call Trace:
    ppr_get+0x40/0xb0 (unreliable)
    __regset_get+0x180/0x1f0
    regset_get_alloc+0x64/0x90
    elf_core_dump+0xb98/0x1b60
    do_coredump+0x1c34/0x24a0
    get_signal+0x71c/0x1410
    do_notify_resume+0x140/0x6f0
    interrupt_exit_user_prepare_main+0x29c/0x320
    interrupt_exit_user_prepare+0x6c/0xa0
    interrupt_return_srr_user+0x8/0x138

Because ppr_get() is trying to copy from a PF_IO_WORKER with a NULL
pt_regs.

Check for a valid pt_regs in both ppc_get/ppr_set, and return an error
if not set. The actual error value doesn't seem to be important here, so
just pick -EINVAL.

Fixes: fa439810cc1b ("powerpc/ptrace: Enable support for NT_PPPC_TAR, NT_PPC_PPR, NT_PPC_DSCR")
Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[mpe: Trim oops in change log, add Fixes & Cc stable]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/d9f63344-fe7c-56ae-b420-4a1a04a2ae4c@kernel.dk