linux-stable.git/arch/powerpc/kernel, branch v6.1.78 Linux kernel stable tree powerpc: Fix build error due to is_valid_bugaddr() 2024-02-05T20:12:46+00:00 Michael Ellerman mpe@ellerman.id.au 2023-11-30T11:44:33+00:00 7ad4b2a6b279ebcc6229cf432beca88526d89950 [ Upstream commit f8d3555355653848082c351fa90775214fb8a4fa ] With CONFIG_GENERIC_BUG=n the build fails with: arch/powerpc/kernel/traps.c:1442:5: error: no previous prototype for ‘is_valid_bugaddr’ [-Werror=missing-prototypes] 1442 | int is_valid_bugaddr(unsigned long addr) | ^~~~~~~~~~~~~~~~ The prototype is only defined, and the function is only needed, when CONFIG_GENERIC_BUG=y, so move the implementation under that. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231130114433.3053544-2-mpe@ellerman.id.au Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit f8d3555355653848082c351fa90775214fb8a4fa ]

With CONFIG_GENERIC_BUG=n the build fails with:

  arch/powerpc/kernel/traps.c:1442:5: error: no previous prototype for ‘is_valid_bugaddr’ [-Werror=missing-prototypes]
  1442 | int is_valid_bugaddr(unsigned long addr)
       |     ^~~~~~~~~~~~~~~~

The prototype is only defined, and the function is only needed, when
CONFIG_GENERIC_BUG=y, so move the implementation under that.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231130114433.3053544-2-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/ftrace: Fix stack teardown in ftrace_no_trace 2023-12-20T16:00:14+00:00 Naveen N Rao naveen@kernel.org 2023-11-30T06:59:47+00:00 1c077acf246c4400df0b9be94aa88650bc31a137 [ Upstream commit 4b3338aaa74d7d4ec5b6734dc298f0db94ec83d2 ] Commit 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind") added use of a new stack frame on ftrace entry to fix stack unwind. However, the commit missed updating the offset used while tearing down the ftrace stack when ftrace is disabled. Fix the same. In addition, the commit missed saving the correct stack pointer in pt_regs. Update the same. Fixes: 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind") Cc: stable@vger.kernel.org # v6.5+ Signed-off-by: Naveen N Rao <naveen@kernel.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 4b3338aaa74d7d4ec5b6734dc298f0db94ec83d2 ]

Commit 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix
stack unwind") added use of a new stack frame on ftrace entry to fix
stack unwind. However, the commit missed updating the offset used while
tearing down the ftrace stack when ftrace is disabled. Fix the same.

In addition, the commit missed saving the correct stack pointer in
pt_regs. Update the same.

Fixes: 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
Cc: stable@vger.kernel.org # v6.5+
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc: Don't clobber f0/vs0 during fp|altivec register save 2023-12-08T07:51:15+00:00 Timothy Pearson tpearson@raptorengineering.com 2023-11-19T15:18:02+00:00 c23b9eaca80c4b4a0c17cc4c9894ff2b60689d04 commit 5e1d824f9a283cbf90f25241b66d1f69adb3835b upstream. During floating point and vector save to thread data f0/vs0 are clobbered by the FPSCR/VSCR store routine. This has been obvserved to lead to userspace register corruption and application data corruption with io-uring. Fix it by restoring f0/vs0 after FPSCR/VSCR store has completed for all the FP, altivec, VMX register save paths. Tested under QEMU in kvm mode, running on a Talos II workstation with dual POWER9 DD2.2 CPUs. Additional detail (mpe): Typically save_fpu() is called from __giveup_fpu() which saves the FP regs and also *turns off FP* in the tasks MSR, meaning the kernel will reload the FP regs from the thread struct before letting the task use FP again. So in that case save_fpu() is free to clobber f0 because the FP regs no longer hold live values for the task. There is another case though, which is the path via: sys_clone() ... copy_process() dup_task_struct() arch_dup_task_struct() flush_all_to_thread() save_all() That path saves the FP regs but leaves them live. That's meant as an optimisation for a process that's using FP/VSX and then calls fork(), leaving the regs live means the parent process doesn't have to take a fault after the fork to get its FP regs back. The optimisation was added in commit 8792468da5e1 ("powerpc: Add the ability to save FPU without giving it up"). That path does clobber f0, but f0 is volatile across function calls, and typically programs reach copy_process() from userspace via a syscall wrapper function. So in normal usage f0 being clobbered across a syscall doesn't cause visible data corruption. But there is now a new path, because io-uring can call copy_process() via create_io_thread() from the signal handling path. That's OK if the signal is handled as part of syscall return, but it's not OK if the signal is handled due to some other interrupt. That path is: interrupt_return_srr_user() interrupt_exit_user_prepare() interrupt_exit_user_prepare_main() do_notify_resume() get_signal() task_work_run() create_worker_cb() create_io_worker() copy_process() dup_task_struct() arch_dup_task_struct() flush_all_to_thread() save_all() if (tsk->thread.regs->msr & MSR_FP) save_fpu() # f0 is clobbered and potentially live in userspace Note the above discussion applies equally to save_altivec(). Fixes: 8792468da5e1 ("powerpc: Add the ability to save FPU without giving it up") Cc: stable@vger.kernel.org # v4.6+ Closes: https://lore.kernel.org/all/480932026.45576726.1699374859845.JavaMail.zimbra@raptorengineeringinc.com/ Closes: https://lore.kernel.org/linuxppc-dev/480221078.47953493.1700206777956.JavaMail.zimbra@raptorengineeringinc.com/ Tested-by: Timothy Pearson <tpearson@raptorengineering.com> Tested-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com> [mpe: Reword change log to describe exact path of corruption & other minor tweaks] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/1921539696.48534988.1700407082933.JavaMail.zimbra@raptorengineeringinc.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 5e1d824f9a283cbf90f25241b66d1f69adb3835b upstream.

During floating point and vector save to thread data f0/vs0 are
clobbered by the FPSCR/VSCR store routine. This has been obvserved to
lead to userspace register corruption and application data corruption
with io-uring.

Fix it by restoring f0/vs0 after FPSCR/VSCR store has completed for
all the FP, altivec, VMX register save paths.

Tested under QEMU in kvm mode, running on a Talos II workstation with
dual POWER9 DD2.2 CPUs.

Additional detail (mpe):

Typically save_fpu() is called from __giveup_fpu() which saves the FP
regs and also *turns off FP* in the tasks MSR, meaning the kernel will
reload the FP regs from the thread struct before letting the task use FP
again. So in that case save_fpu() is free to clobber f0 because the FP
regs no longer hold live values for the task.

There is another case though, which is the path via:
  sys_clone()
    ...
    copy_process()
      dup_task_struct()
        arch_dup_task_struct()
          flush_all_to_thread()
            save_all()

That path saves the FP regs but leaves them live. That's meant as an
optimisation for a process that's using FP/VSX and then calls fork(),
leaving the regs live means the parent process doesn't have to take a
fault after the fork to get its FP regs back. The optimisation was added
in commit 8792468da5e1 ("powerpc: Add the ability to save FPU without
giving it up").

That path does clobber f0, but f0 is volatile across function calls,
and typically programs reach copy_process() from userspace via a syscall
wrapper function. So in normal usage f0 being clobbered across a
syscall doesn't cause visible data corruption.

But there is now a new path, because io-uring can call copy_process()
via create_io_thread() from the signal handling path. That's OK if the
signal is handled as part of syscall return, but it's not OK if the
signal is handled due to some other interrupt.

That path is:

interrupt_return_srr_user()
  interrupt_exit_user_prepare()
    interrupt_exit_user_prepare_main()
      do_notify_resume()
        get_signal()
          task_work_run()
            create_worker_cb()
              create_io_worker()
                copy_process()
                  dup_task_struct()
                    arch_dup_task_struct()
                      flush_all_to_thread()
                        save_all()
                          if (tsk->thread.regs->msr & MSR_FP)
                            save_fpu()
                            # f0 is clobbered and potentially live in userspace

Note the above discussion applies equally to save_altivec().

Fixes: 8792468da5e1 ("powerpc: Add the ability to save FPU without giving it up")
Cc: stable@vger.kernel.org # v4.6+
Closes: https://lore.kernel.org/all/480932026.45576726.1699374859845.JavaMail.zimbra@raptorengineeringinc.com/
Closes: https://lore.kernel.org/linuxppc-dev/480221078.47953493.1700206777956.JavaMail.zimbra@raptorengineeringinc.com/
Tested-by: Timothy Pearson <tpearson@raptorengineering.com>
Tested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com>
[mpe: Reword change log to describe exact path of corruption & other minor tweaks]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/1921539696.48534988.1700407082933.JavaMail.zimbra@raptorengineeringinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
KVM: PPC: Book3S HV: Fix KVM_RUN clobbering FP/VEC user registers 2023-12-08T07:51:15+00:00 Nicholas Piggin npiggin@gmail.com 2023-11-22T02:58:11+00:00 e6bc42fae6b85efac58780bbd5f523bb4eab26c1 commit dc158d23b33df9033bcc8e7117e8591dd2f9d125 upstream. Before running a guest, the host process (e.g., QEMU) FP/VEC registers are saved if they were being used, similarly to when the kernel uses FP registers. The guest values are then loaded into regs, and the host process registers will be restored lazily when it uses FP/VEC. KVM HV has a bug here: the host process registers do get saved, but the user MSR bits remain enabled, which indicates the registers are valid for the process. After they are clobbered by running the guest, this valid indication causes the host process to take on the FP/VEC register values of the guest. Fixes: 34e119c96b2b ("KVM: PPC: Book3S HV P9: Reduce mtmsrd instructions required to save host SPRs") Cc: stable@vger.kernel.org # v5.17+ Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231122025811.2973-1-npiggin@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit dc158d23b33df9033bcc8e7117e8591dd2f9d125 upstream.

Before running a guest, the host process (e.g., QEMU) FP/VEC registers
are saved if they were being used, similarly to when the kernel uses FP
registers. The guest values are then loaded into regs, and the host
process registers will be restored lazily when it uses FP/VEC.

KVM HV has a bug here: the host process registers do get saved, but the
user MSR bits remain enabled, which indicates the registers are valid
for the process. After they are clobbered by running the guest, this
valid indication causes the host process to take on the FP/VEC register
values of the guest.

Fixes: 34e119c96b2b ("KVM: PPC: Book3S HV P9: Reduce mtmsrd instructions required to save host SPRs")
Cc: stable@vger.kernel.org # v5.17+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231122025811.2973-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
powerpc: Only define __parse_fpscr() when required 2023-11-20T10:52:12+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2023-09-22T12:33:13+00:00 9d4f7441cddd3af0a67db42375f707fc9f459559 [ Upstream commit c7e0d9bb9154c6e6b2ac8746faba27b53393f25e ] Clang 17 reports: arch/powerpc/kernel/traps.c:1167:19: error: unused function '__parse_fpscr' [-Werror,-Wunused-function] __parse_fpscr() is called from two sites. First call is guarded by #ifdef CONFIG_PPC_FPU_REGS Second call is guarded by CONFIG_MATH_EMULATION which selects CONFIG_PPC_FPU_REGS. So only define __parse_fpscr() when CONFIG_PPC_FPU_REGS is defined. Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202309210327.WkqSd5Bq-lkp@intel.com/ Fixes: b6254ced4da6 ("powerpc/signal: Don't manage floating point regs when no FPU") Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/5de2998c57f3983563b27b39228ea9a7229d4110.1695385984.git.christophe.leroy@csgroup.eu Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit c7e0d9bb9154c6e6b2ac8746faba27b53393f25e ]

Clang 17 reports:

arch/powerpc/kernel/traps.c:1167:19: error: unused function '__parse_fpscr' [-Werror,-Wunused-function]

__parse_fpscr() is called from two sites. First call is guarded
by #ifdef CONFIG_PPC_FPU_REGS

Second call is guarded by CONFIG_MATH_EMULATION which selects
CONFIG_PPC_FPU_REGS.

So only define __parse_fpscr() when CONFIG_PPC_FPU_REGS is defined.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309210327.WkqSd5Bq-lkp@intel.com/
Fixes: b6254ced4da6 ("powerpc/signal: Don't manage floating point regs when no FPU")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/5de2998c57f3983563b27b39228ea9a7229d4110.1695385984.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/mm: Fix boot crash with FLATMEM 2023-11-08T13:11:02+00:00 Michael Ellerman mpe@ellerman.id.au 2023-10-23T11:25:00+00:00 ed0ba37e7b9b2f9669d3ed0634356aef04ee0ef1 [ Upstream commit daa9ada2093ed23d52b4c1fe6e13cf78f55cc85f ] Erhard reported that his G5 was crashing with v6.6-rc kernels: mpic: Setting up HT PICs workarounds for U3/U4 BUG: Unable to handle kernel data access at 0xfeffbb62ffec65fe Faulting instruction address: 0xc00000000005dc40 Oops: Kernel access of bad area, sig: 11 [#1] BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 PowerMac Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Tainted: G T 6.6.0-rc3-PMacGS #1 Hardware name: PowerMac11,2 PPC970MP 0x440101 PowerMac NIP: c00000000005dc40 LR: c000000000066660 CTR: c000000000007730 REGS: c0000000022bf510 TRAP: 0380 Tainted: G T (6.6.0-rc3-PMacGS) MSR: 9000000000001032 <SF,HV,ME,IR,DR,RI> CR: 44004242 XER: 00000000 IRQMASK: 3 GPR00: 0000000000000000 c0000000022bf7b0 c0000000010c0b00 00000000000001ac GPR04: 0000000003c80000 0000000000000300 c0000000f20001ae 0000000000000300 GPR08: 0000000000000006 feffbb62ffec65ff 0000000000000001 0000000000000000 GPR12: 9000000000001032 c000000002362000 c000000000f76b80 000000000349ecd8 GPR16: 0000000002367ba8 0000000002367f08 0000000000000006 0000000000000000 GPR20: 00000000000001ac c000000000f6f920 c0000000022cd985 000000000000000c GPR24: 0000000000000300 00000003b0a3691d c0003e008030000e 0000000000000000 GPR28: c00000000000000c c0000000f20001ee feffbb62ffec65fe 00000000000001ac NIP hash_page_do_lazy_icache+0x50/0x100 LR __hash_page_4K+0x420/0x590 Call Trace: hash_page_mm+0x364/0x6f0 do_hash_fault+0x114/0x2b0 data_access_common_virt+0x198/0x1f0 --- interrupt: 300 at mpic_init+0x4bc/0x10c4 NIP: c000000002020a5c LR: c000000002020a04 CTR: 0000000000000000 REGS: c0000000022bf9f0 TRAP: 0300 Tainted: G T (6.6.0-rc3-PMacGS) MSR: 9000000000001032 <SF,HV,ME,IR,DR,RI> CR: 24004248 XER: 00000000 DAR: c0003e008030000e DSISR: 40000000 IRQMASK: 1 ... NIP mpic_init+0x4bc/0x10c4 LR mpic_init+0x464/0x10c4 --- interrupt: 300 pmac_setup_one_mpic+0x258/0x2dc pmac_pic_init+0x28c/0x3d8 init_IRQ+0x90/0x140 start_kernel+0x57c/0x78c start_here_common+0x1c/0x20 A bisect pointed to the breakage beginning with commit 9fee28baa601 ("powerpc: implement the new page table range API"). Analysis of the oops pointed to a struct page with a corrupted compound_head being loaded via page_folio() -> _compound_head() in hash_page_do_lazy_icache(). The access by the mpic code is to an MMIO address, so the expectation is that the struct page for that address would be initialised by init_unavailable_range(), as pointed out by Aneesh. Instrumentation showed that was not the case, which eventually lead to the realisation that pfn_valid() was returning false for that address, causing the struct page to not be initialised. Because the system is using FLATMEM, the version of pfn_valid() in memory_model.h is used: static inline int pfn_valid(unsigned long pfn) { ... return pfn >= pfn_offset && (pfn - pfn_offset) < max_mapnr; } Which relies on max_mapnr being initialised. Early in boot max_mapnr is zero meaning no PFNs are valid. max_mapnr is initialised in mem_init() called via: start_kernel() mm_core_init() # init/main.c:928 mem_init() But that is too late for the usage in init_unavailable_range() called via: start_kernel() setup_arch() # init/main.c:893 paging_init() free_area_init() init_unavailable_range() Although max_mapnr is currently set in mem_init(), the value is actually already available much earlier, as soon as mem_topology_setup() has completed, which is also before paging_init() is called. So move the initialisation there, which causes paging_init() to correctly initialise the struct page and fixes the bug. This bug seems to have been lurking for years, but went unnoticed because the pre-folio code was inspecting the uninitialised page->flags but not dereferencing it. Thanks to Erhard and Aneesh for help debugging. Reported-by: Erhard Furtner <erhard_f@mailbox.org> Closes: https://lore.kernel.org/all/20230929132750.3cd98452@yea/ Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231023112500.1550208-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit daa9ada2093ed23d52b4c1fe6e13cf78f55cc85f ]

Erhard reported that his G5 was crashing with v6.6-rc kernels:

  mpic: Setting up HT PICs workarounds for U3/U4
  BUG: Unable to handle kernel data access at 0xfeffbb62ffec65fe
  Faulting instruction address: 0xc00000000005dc40
  Oops: Kernel access of bad area, sig: 11 [#1]
  BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 PowerMac
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Tainted: G                T  6.6.0-rc3-PMacGS #1
  Hardware name: PowerMac11,2 PPC970MP 0x440101 PowerMac
  NIP:  c00000000005dc40 LR: c000000000066660 CTR: c000000000007730
  REGS: c0000000022bf510 TRAP: 0380   Tainted: G                T (6.6.0-rc3-PMacGS)
  MSR:  9000000000001032 <SF,HV,ME,IR,DR,RI>  CR: 44004242  XER: 00000000
  IRQMASK: 3
  GPR00: 0000000000000000 c0000000022bf7b0 c0000000010c0b00 00000000000001ac
  GPR04: 0000000003c80000 0000000000000300 c0000000f20001ae 0000000000000300
  GPR08: 0000000000000006 feffbb62ffec65ff 0000000000000001 0000000000000000
  GPR12: 9000000000001032 c000000002362000 c000000000f76b80 000000000349ecd8
  GPR16: 0000000002367ba8 0000000002367f08 0000000000000006 0000000000000000
  GPR20: 00000000000001ac c000000000f6f920 c0000000022cd985 000000000000000c
  GPR24: 0000000000000300 00000003b0a3691d c0003e008030000e 0000000000000000
  GPR28: c00000000000000c c0000000f20001ee feffbb62ffec65fe 00000000000001ac
  NIP hash_page_do_lazy_icache+0x50/0x100
  LR  __hash_page_4K+0x420/0x590
  Call Trace:
    hash_page_mm+0x364/0x6f0
    do_hash_fault+0x114/0x2b0
    data_access_common_virt+0x198/0x1f0
  --- interrupt: 300 at mpic_init+0x4bc/0x10c4
  NIP:  c000000002020a5c LR: c000000002020a04 CTR: 0000000000000000
  REGS: c0000000022bf9f0 TRAP: 0300   Tainted: G                T (6.6.0-rc3-PMacGS)
  MSR:  9000000000001032 <SF,HV,ME,IR,DR,RI>  CR: 24004248  XER: 00000000
  DAR: c0003e008030000e DSISR: 40000000 IRQMASK: 1
  ...
  NIP mpic_init+0x4bc/0x10c4
  LR  mpic_init+0x464/0x10c4
  --- interrupt: 300
    pmac_setup_one_mpic+0x258/0x2dc
    pmac_pic_init+0x28c/0x3d8
    init_IRQ+0x90/0x140
    start_kernel+0x57c/0x78c
    start_here_common+0x1c/0x20

A bisect pointed to the breakage beginning with commit 9fee28baa601 ("powerpc:
implement the new page table range API").

Analysis of the oops pointed to a struct page with a corrupted
compound_head being loaded via page_folio() -> _compound_head() in
hash_page_do_lazy_icache().

The access by the mpic code is to an MMIO address, so the expectation
is that the struct page for that address would be initialised by
init_unavailable_range(), as pointed out by Aneesh.

Instrumentation showed that was not the case, which eventually lead to
the realisation that pfn_valid() was returning false for that address,
causing the struct page to not be initialised.

Because the system is using FLATMEM, the version of pfn_valid() in
memory_model.h is used:

static inline int pfn_valid(unsigned long pfn)
{
	...
	return pfn >= pfn_offset && (pfn - pfn_offset) < max_mapnr;
}

Which relies on max_mapnr being initialised. Early in boot max_mapnr is
zero meaning no PFNs are valid.

max_mapnr is initialised in mem_init() called via:

  start_kernel()
    mm_core_init()  # init/main.c:928
      mem_init()

But that is too late for the usage in init_unavailable_range() called via:

  start_kernel()
    setup_arch()    # init/main.c:893
      paging_init()
        free_area_init()
          init_unavailable_range()

Although max_mapnr is currently set in mem_init(), the value is actually
already available much earlier, as soon as mem_topology_setup() has
completed, which is also before paging_init() is called. So move the
initialisation there, which causes paging_init() to correctly initialise
the struct page and fixes the bug.

This bug seems to have been lurking for years, but went unnoticed
because the pre-folio code was inspecting the uninitialised page->flags
but not dereferencing it.

Thanks to Erhard and Aneesh for help debugging.

Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Closes: https://lore.kernel.org/all/20230929132750.3cd98452@yea/
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231023112500.1550208-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/85xx: Fix math emulation exception 2023-11-08T13:10:58+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2023-09-25T15:55:51+00:00 c64c237275b46c52e97cb020ed10d2028f214be4 [ Upstream commit 8e8a12ecbc86700b5e1a3596ce2b3c43dafad336 ] Booting mpc85xx_defconfig kernel on QEMU leads to: Bad trap at PC: fe9bab0, SR: 2d000, vector=800 awk[82]: unhandled trap (5) at 0 nip fe9bab0 lr fe9e01c code 5 in libc-2.27.so[fe5a000+17a000] awk[82]: code: 3aa00000 3a800010 4bffe03c 9421fff0 7ca62b78 38a00000 93c10008 83c10008 awk[82]: code: 38210010 4bffdec8 9421ffc0 7c0802a6 <fc00048e> d8010008 4815190d 93810030 Trace/breakpoint trap WARNING: no useful console This is because allthough CONFIG_MATH_EMULATION is selected, Exception 800 calls unknown_exception(). Call emulation_assist_interrupt() instead. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/066caa6d9480365da9b8ed83692d7101e10ac5f8.1695657339.git.christophe.leroy@csgroup.eu Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 8e8a12ecbc86700b5e1a3596ce2b3c43dafad336 ]

Booting mpc85xx_defconfig kernel on QEMU leads to:

Bad trap at PC: fe9bab0, SR: 2d000, vector=800
awk[82]: unhandled trap (5) at 0 nip fe9bab0 lr fe9e01c code 5 in libc-2.27.so[fe5a000+17a000]
awk[82]: code: 3aa00000 3a800010 4bffe03c 9421fff0 7ca62b78 38a00000 93c10008 83c10008
awk[82]: code: 38210010 4bffdec8 9421ffc0 7c0802a6 <fc00048e> d8010008 4815190d 93810030
Trace/breakpoint trap
WARNING: no useful console

This is because allthough CONFIG_MATH_EMULATION is selected,
Exception 800 calls unknown_exception().

Call emulation_assist_interrupt() instead.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/066caa6d9480365da9b8ed83692d7101e10ac5f8.1695657339.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/47x: Fix 47x syscall return crash 2023-10-19T21:08:56+00:00 Michael Ellerman mpe@ellerman.id.au 2023-10-10T11:47:50+00:00 8ac2689502f986a46f4221e239d4ff2897f1ccb3 commit f0eee815babed70a749d2496a7678be5b45b4c14 upstream. 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 ]--- The problem is in ret_from_syscall where the check for icache_44x_need_flush is done. When the flush is needed the code jumps out-of-line to do the flush, and then intends to jump back to continue the syscall return. However the branch back to label 1b doesn't return to the correct location, instead branching back just prior to the return to userspace, causing bogus register values to be used by the rfi. The breakage was introduced by commit 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") which inadvertently removed the "1" label and reused it elsewhere. Fix it by adding named local labels in the correct locations. Note that the return label needs to be outside the ifdef so that CONFIG_PPC_47x=n compiles. Fixes: 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") Cc: stable@vger.kernel.org # v5.12+ Reported-by: Eddie James <eajames@linux.ibm.com> Tested-by: Eddie James <eajames@linux.ibm.com> Link: https://lore.kernel.org/linuxppc-dev/fdaadc46-7476-9237-e104-1d2168526e72@linux.ibm.com/ Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Link: https://msgid.link/20231010114750.847794-1-mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit f0eee815babed70a749d2496a7678be5b45b4c14 upstream.

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 ]---

The problem is in ret_from_syscall where the check for
icache_44x_need_flush is done. When the flush is needed the code jumps
out-of-line to do the flush, and then intends to jump back to continue
the syscall return.

However the branch back to label 1b doesn't return to the correct
location, instead branching back just prior to the return to userspace,
causing bogus register values to be used by the rfi.

The breakage was introduced by commit 6f76a01173cc
("powerpc/syscall: implement system call entry/exit logic in C for PPC32") which
inadvertently removed the "1" label and reused it elsewhere.

Fix it by adding named local labels in the correct locations. Note that
the return label needs to be outside the ifdef so that CONFIG_PPC_47x=n
compiles.

Fixes: 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32")
Cc: stable@vger.kernel.org # v5.12+
Reported-by: Eddie James <eajames@linux.ibm.com>
Tested-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/linuxppc-dev/fdaadc46-7476-9237-e104-1d2168526e72@linux.ibm.com/
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://msgid.link/20231010114750.847794-1-mpe@ellerman.id.au
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
powerpc/watchpoints: Annotate atomic context in more places 2023-10-06T12:56:57+00:00 Benjamin Gray bgray@linux.ibm.com 2023-08-29T06:34:57+00:00 c93aa8cfaec493e21aed78438f7cfb341fdaec12 [ Upstream commit 27646b2e02b096a6936b3e3b6ba334ae20763eab ] It can be easy to miss that the notifier mechanism invokes the callbacks in an atomic context, so add some comments to that effect on the two handlers we register here. Signed-off-by: Benjamin Gray <bgray@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20230829063457.54157-4-bgray@linux.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 27646b2e02b096a6936b3e3b6ba334ae20763eab ]

It can be easy to miss that the notifier mechanism invokes the callbacks
in an atomic context, so add some comments to that effect on the two
handlers we register here.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230829063457.54157-4-bgray@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/watchpoint: Disable pagefaults when getting user instruction 2023-10-06T12:56:57+00:00 Benjamin Gray bgray@linux.ibm.com 2023-08-29T06:34:56+00:00 3632e9fd82d030491c8643cb61d36a2371e83a02 [ Upstream commit 3241f260eb830d27d09cc604690ec24533fdb433 ] This is called in an atomic context, so is not allowed to sleep if a user page needs to be faulted in and has nowhere it can be deferred to. The pagefault_disabled() function is documented as preventing user access methods from sleeping. In practice the page will be mapped in nearly always because we are reading the instruction that just triggered the watchpoint trap. Signed-off-by: Benjamin Gray <bgray@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20230829063457.54157-3-bgray@linux.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 3241f260eb830d27d09cc604690ec24533fdb433 ]

This is called in an atomic context, so is not allowed to sleep if a
user page needs to be faulted in and has nowhere it can be deferred to.
The pagefault_disabled() function is documented as preventing user
access methods from sleeping.

In practice the page will be mapped in nearly always because we are
reading the instruction that just triggered the watchpoint trap.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230829063457.54157-3-bgray@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>