linux.git/arch/s390, branch v5.9

mm/gup: fix gup_fast with dynamic page table folding

2020-09-26T17:33:57+00:00

Currently to make sure that every page table entry is read just once
gup_fast walks perform READ_ONCE and pass pXd value down to the next
gup_pXd_range function by value e.g.:

  static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
                           unsigned int flags, struct page **pages, int *nr)
  ...
          pudp = pud_offset(&p4d, addr);

This function passes a reference on that local value copy to pXd_offset,
and might get the very same pointer in return.  This happens when the
level is folded (on most arches), and that pointer should not be
iterated.

On s390 due to the fact that each task might have different 5,4 or
3-level address translation and hence different levels folded the logic
is more complex and non-iteratable pointer to a local copy leads to
severe problems.

Here is an example of what happens with gup_fast on s390, for a task
with 3-level paging, crossing a 2 GB pud boundary:

  // addr = 0x1007ffff000, end = 0x10080001000
  static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
                           unsigned int flags, struct page **pages, int *nr)
  {
        unsigned long next;
        pud_t *pudp;

        // pud_offset returns &p4d itself (a pointer to a value on stack)
        pudp = pud_offset(&p4d, addr);
        do {
                // on second iteratation reading "random" stack value
                pud_t pud = READ_ONCE(*pudp);

                // next = 0x10080000000, due to PUD_SIZE/MASK != PGDIR_SIZE/MASK on s390
                next = pud_addr_end(addr, end);
                ...
        } while (pudp++, addr = next, addr != end); // pudp++ iterating over stack

        return 1;
  }

This happens since s390 moved to common gup code with commit
d1874a0c2805 ("s390/mm: make the pxd_offset functions more robust") and
commit 1a42010cdc26 ("s390/mm: convert to the generic
get_user_pages_fast code").

s390 tried to mimic static level folding by changing pXd_offset
primitives to always calculate top level page table offset in pgd_offset
and just return the value passed when pXd_offset has to act as folded.

What is crucial for gup_fast and what has been overlooked is that
PxD_SIZE/MASK and thus pXd_addr_end should also change correspondingly.
And the latter is not possible with dynamic folding.

To fix the issue in addition to pXd values pass original pXdp pointers
down to gup_pXd_range functions.  And introduce pXd_offset_lockless
helpers, which take an additional pXd entry value parameter.  This has
already been discussed in

  https://lkml.kernel.org/r/20190418100218.0a4afd51@mschwideX1

Fixes: 1a42010cdc26 ("s390/mm: convert to the generic get_user_pages_fast code")
Signed-off-by: Vasily Gorbik 
Signed-off-by: Andrew Morton 
Reviewed-by: Gerald Schaefer 
Reviewed-by: Alexander Gordeev 
Reviewed-by: Jason Gunthorpe 
Reviewed-by: Mike Rapoport 
Reviewed-by: John Hubbard 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Dave Hansen 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Michael Ellerman 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Jeff Dike 
Cc: Richard Weinberger 
Cc: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: Arnd Bergmann 
Cc: Andrey Ryabinin 
Cc: Heiko Carstens 
Cc: Christian Borntraeger 
Cc: Claudio Imbrenda 
Cc: 	[5.2+]
Link: https://lkml.kernel.org/r/patch.git-943f1e5dcff2.your-ad-here.call-01599856292-ext-8676@work.hours
Signed-off-by: Linus Torvalds

s390: add 3f program exception handler

2020-09-14T08:08:07+00:00

Program exception 3f (secure storage violation) can only be detected
when the CPU is running in SIE with a format 4 state description,
e.g. running a protected guest. Because of this and because user
space partly controls the guest memory mapping and can trigger this
exception, we want to send a SIGSEGV to the process running the guest
and not panic the kernel.

Signed-off-by: Janosch Frank 
Cc:  # 5.7
Fixes: 084ea4d611a3 ("s390/mm: add (non)secure page access exceptions handlers")
Reviewed-by: Claudio Imbrenda 
Reviewed-by: Cornelia Huck 
Acked-by: Christian Borntraeger 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/pci: fix leak of DMA tables on hard unplug

2020-09-14T08:08:07+00:00

commit f606b3ef47c9 ("s390/pci: adapt events for zbus") removed the
zpci_disable_device() call for a zPCI event with PEC 0x0304 because
the device is already deconfigured by the platform.
This however skips the Linux side of the disable in particular it leads
to leaking the DMA tables and bitmaps because zpci_dma_exit_device() is
never called on the device.

If the device transitions to the Reserved state we call zpci_zdev_put()
but zpci_release_device() will not call zpci_disable_device() because
the state of the zPCI function is already ZPCI_FN_STATE_STANDBY.

If the device is put into the Standby state, zpci_disable_device() is
not called and the device is assumed to have been put in Standby through
platform action.
At this point the device may be removed by a subsequent event with PEC
0x0308 or 0x0306 which calls zpci_zdev_put() with the same problem
as above or the device may be configured again in which case
zpci_disable_device() is also not called.

Fix this by calling zpci_disable_device() explicitly for PEC 0x0304 as
before. To make it more clear that zpci_disable_device() may be called,
even if the lower level device has already been disabled by the
platform, add a comment to zpci_disable_device().

Cc:  # 5.8
Fixes: f606b3ef47c9 ("s390/pci: adapt events for zbus")
Signed-off-by: Niklas Schnelle 
Signed-off-by: Vasily Gorbik

s390/init: add missing __init annotations

2020-09-14T08:08:07+00:00

Add __init to reserve_memory_end, reserve_oldmem and remove_oldmem.
Sometimes these functions are not inlined, and then the build
complains about section mismatch.

Signed-off-by: Ilya Leoshkevich 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/idle: fix suspicious RCU usage

2020-09-14T08:08:07+00:00

After commit eb1f00237aca ("lockdep,trace: Expose tracepoints") the
lock tracepoints are visible to lockdep and RCU-lockdep is finding a
bunch more RCU violations that were previously hidden.

Switch the idle->seqcount over to using raw_write_*() to avoid the
lockdep annotation and thus the lock tracepoints.

Reported-by: Guenter Roeck 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390: update defconfigs

2020-09-02T11:17:05+00:00

Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390: fix GENERIC_LOCKBREAK dependency typo in Kconfig

2020-09-02T11:17:05+00:00

Commit fa686453053b ("sched/rt, s390: Use CONFIG_PREEMPTION")
changed a bunch of uses of CONFIG_PREEMPT to _PREEMPTION.
Except in the Kconfig it used two T's. That's the only place
in the system where that spelling exists, so let's fix that.

Fixes: fa686453053b ("sched/rt, s390: Use CONFIG_PREEMPTION")
Cc:  # 5.6
Signed-off-by: Eric Farman 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

Merge tag 'locking-urgent-2020-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-08-30T18:43:50+00:00

Pull locking fixes from Thomas Gleixner:
 "A set of fixes for lockdep, tracing and RCU:

   - Prevent recursion by using raw_cpu_* operations

   - Fixup the interrupt state in the cpu idle code to be consistent

   - Push rcu_idle_enter/exit() invocations deeper into the idle path so
     that the lock operations are inside the RCU watching sections

   - Move trace_cpu_idle() into generic code so it's called before RCU
     goes idle.

   - Handle raw_local_irq* vs. local_irq* operations correctly

   - Move the tracepoints out from under the lockdep recursion handling
     which turned out to be fragile and inconsistent"

* tag 'locking-urgent-2020-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lockdep,trace: Expose tracepoints
  lockdep: Only trace IRQ edges
  mips: Implement arch_irqs_disabled()
  arm64: Implement arch_irqs_disabled()
  nds32: Implement arch_irqs_disabled()
  locking/lockdep: Cleanup
  x86/entry: Remove unused THUNKs
  cpuidle: Move trace_cpu_idle() into generic code
  cpuidle: Make CPUIDLE_FLAG_TLB_FLUSHED generic
  sched,idle,rcu: Push rcu_idle deeper into the idle path
  cpuidle: Fixup IRQ state
  lockdep: Use raw_cpu_*() for per-cpu variables

s390/vmem: fix vmem_add_range for 4-level paging

2020-08-26T16:07:05+00:00

The kernel currently crashes if 4-level paging is used. Add missing
p4d_populate for just allocated pud entry.

Fixes: 3e0d3e408e63 ("s390/vmem: consolidate vmem_add_range() and vmem_remove_range()")
Reviewed-by: Gerald Schaefer 
Signed-off-by: Vasily Gorbik

s390: don't trace preemption in percpu macros

2020-08-26T16:07:04+00:00

Since commit a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context}
to per-cpu variables") the lockdep code itself uses percpu variables. This
leads to recursions because the percpu macros are calling preempt_enable()
which might call trace_preempt_on().

Signed-off-by: Sven Schnelle 
Reviewed-by: Vasily Gorbik 
Signed-off-by: Vasily Gorbik