linux-stable.git/arch/powerpc, branch v4.4.76

powerpc/eeh: Enable IO path on permanent error

2017-07-05T12:37:18+00:00

[ Upstream commit 387bbc974f6adf91aa635090f73434ed10edd915 ]

We give up recovery on permanent error, simply shutdown the affected
devices and remove them. If the devices can't be put into quiet state,
they spew more traffic that is likely to cause another unexpected EEH
error. This was observed on "p8dtu2u" machine:

   0002:00:00.0 PCI bridge: IBM Device 03dc
   0002:01:00.0 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)
   0002:01:00.1 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)
   0002:01:00.2 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)
   0002:01:00.3 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)

On P8 PowerNV platform, the IO path is frozen when shutdowning the
devices, meaning the memory registers are inaccessible. It is why
the devices can't be put into quiet state before removing them.
This fixes the issue by enabling IO path prior to putting the devices
into quiet state.

Reported-by: Pridhiviraj Paidipeddi 
Signed-off-by: Gavin Shan 
Acked-by: Russell Currey 
Signed-off-by: Michael Ellerman 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

powerpc/slb: Force a full SLB flush when we insert for a bad EA

2017-06-29T10:48:52+00:00

[Note this patch is not upstream. The bug fix was fixed differently in
upstream prior to the bug being identified.]

The SLB miss handler calls slb_allocate_realmode() in order to create an
SLB entry for the faulting address. At the very start of that function
we check that the faulting Effective Address (EA) is less than
PGTABLE_RANGE (ignoring the region), ie. is it an address which could
possibly fit in the virtual address space.

For an EA which fails that test, we branch out of line (to label 8), but
we still go on to create an SLB entry for the address. The SLB entry we
create has a VSID of 0, which means it will never match anything in the
hash table and so can't actually translate to a physical address.

However that SLB entry will be inserted in the SLB, and so needs to be
managed properly like any other SLB entry. In particular we need to
insert the SLB entry in the SLB cache, so that it will be flushed when
the process is descheduled.

And that is where the bugs begin. The first bug is that slb_finish_load()
uses cr7 to decide if it should insert the SLB entry into the SLB cache.
When we come from the invalid EA case we don't set cr7, it just has some
junk value from userspace. So we may or may not insert the SLB entry in
the SLB cache. If we fail to insert it, we may then incorrectly leave it
in the SLB when the process is descheduled.

The second bug is that even if we do happen to add the entry to the SLB
cache, we do not have enough bits in the SLB cache to remember the full
ESID value for very large EAs.

For example if a process branches to 0x788c545a18000000, that results in
a 256MB SLB entry with an ESID of 0x788c545a1. But each entry in the SLB
cache is only 32-bits, meaning we truncate the ESID to 0x88c545a1. This
has the same effect as the first bug, we incorrectly leave the SLB entry
in the SLB when the process is descheduled.

When a process accesses an invalid EA it results in a SEGV signal being
sent to the process, which typically results in the process being
killed. Process death isn't instantaneous however, the process may catch
the SEGV signal and continue somehow, or the kernel may start writing a
core dump for the process, either of which means it's possible for the
process to be preempted while its processing the SEGV but before it's
been killed.

If that happens, when the process is scheduled back onto the CPU we will
allocate a new SLB entry for the NIP, which will insert a second entry
into the SLB for the bad EA. Because we never flushed the original
entry, due to either bug one or two, we now have two SLB entries that
match the same EA.

If another access is made to that EA, either by the process continuing
after catching the SEGV, or by a second process accessing the same bad
EA on the same CPU, we will trigger an SLB multi-hit machine check
exception. This has been observed happening in the wild.

The fix is when we hit the invalid EA case, we mark the SLB cache as
being full. This causes us to not insert the truncated ESID into the SLB
cache, and means when the process is switched out we will flush the
entire SLB. Note that this works both for the original fault and for a
subsequent call to slb_allocate_realmode() from switch_slb().

Because we mark the SLB cache as full, it doesn't really matter what
value is in cr7, but rather than leaving it as something random we set
it to indicate the address was a kernel address. That also skips the
attempt to insert it in the SLB cache which is a nice side effect.

Another way to fix the bug would be to make the entries in the SLB cache
wider, so that we don't truncate the ESID. However this would be a more
intrusive change as it alters the size and layout of the paca.

This bug was fixed in upstream by commit f0f558b131db ("powerpc/mm:
Preserve CFAR value on SLB miss caused by access to bogus address"),
which changed the way we handle a bad EA entirely removing this bug in
the process.

Signed-off-by: Michael Ellerman 
Reviewed-by: Paul Mackerras 
Signed-off-by: Greg Kroah-Hartman

powerpc/kprobes: Pause function_graph tracing during jprobes handling

2017-06-29T10:48:51+00:00

commit a9f8553e935f26cb5447f67e280946b0923cd2dc upstream.

This fixes a crash when function_graph and jprobes are used together.
This is essentially commit 237d28db036e ("ftrace/jprobes/x86: Fix
conflict between jprobes and function graph tracing"), but for powerpc.

Jprobes breaks function_graph tracing since the jprobe hook needs to use
jprobe_return(), which never returns back to the hook, but instead to
the original jprobe'd function. The solution is to momentarily pause
function_graph tracing before invoking the jprobe hook and re-enable it
when returning back to the original jprobe'd function.

Fixes: 6794c78243bf ("powerpc64: port of the function graph tracer")
Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Acked-by: Steven Rostedt (VMware) 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

KVM: PPC: Book3S HV: Preserve userspace HTM state properly

2017-06-29T10:48:51+00:00

commit 46a704f8409f79fd66567ad3f8a7304830a84293 upstream.

If userspace attempts to call the KVM_RUN ioctl when it has hardware
transactional memory (HTM) enabled, the values that it has put in the
HTM-related SPRs TFHAR, TFIAR and TEXASR will get overwritten by
guest values.  To fix this, we detect this condition and save those
SPR values in the thread struct, and disable HTM for the task.  If
userspace goes to access those SPRs or the HTM facility in future,
a TM-unavailable interrupt will occur and the handler will reload
those SPRs and re-enable HTM.

If userspace has started a transaction and suspended it, we would
currently lose the transactional state in the guest entry path and
would almost certainly get a "TM Bad Thing" interrupt, which would
cause the host to crash.  To avoid this, we detect this case and
return from the KVM_RUN ioctl with an EINVAL error, with the KVM
exit reason set to KVM_EXIT_FAIL_ENTRY.

Fixes: b005255e12a3 ("KVM: PPC: Book3S HV: Context-switch new POWER8 SPRs", 2014-01-08)
Signed-off-by: Paul Mackerras 
Signed-off-by: Greg Kroah-Hartman

mm: larger stack guard gap, between vmas

2017-06-26T05:13:11+00:00

commit 1be7107fbe18eed3e319a6c3e83c78254b693acb upstream.

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov 
Original-patch-by: Michal Hocko 
Signed-off-by: Hugh Dickins 
Acked-by: Michal Hocko 
Tested-by: Helge Deller  # parisc
Signed-off-by: Linus Torvalds 
[wt: backport to 4.11: adjust context]
[wt: backport to 4.9: adjust context ; kernel doc was not in admin-guide]
[wt: backport to 4.4: adjust context ; drop ppc hugetlb_radix changes]
Signed-off-by: Willy Tarreau 
[gkh: minor build fixes for 4.4]
Signed-off-by: Greg Kroah-Hartman

powerpc/hotplug-mem: Fix missing endian conversion of aa_index

2017-06-14T11:16:25+00:00

commit dc421b200f91930c9c6a9586810ff8c232cf10fc upstream.

When adding or removing memory, the aa_index (affinity value) for the
memblock must also be converted to match the endianness of the rest
of the 'ibm,dynamic-memory' property.  Otherwise, subsequent retrieval
of the attribute will likely lead to non-existent nodes, followed by
using the default node in the code inappropriately.

Fixes: 5f97b2a0d176 ("powerpc/pseries: Implement memory hotplug add in the kernel")
Signed-off-by: Michael Bringmann 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/numa: Fix percpu allocations to be NUMA aware

2017-06-14T11:16:25+00:00

commit ba4a648f12f4cd0a8003dd229b6ca8a53348ee4b upstream.

In commit 8c272261194d ("powerpc/numa: Enable USE_PERCPU_NUMA_NODE_ID"), we
switched to the generic implementation of cpu_to_node(), which uses a percpu
variable to hold the NUMA node for each CPU.

Unfortunately we neglected to notice that we use cpu_to_node() in the allocation
of our percpu areas, leading to a chicken and egg problem. In practice what
happens is when we are setting up the percpu areas, cpu_to_node() reports that
all CPUs are on node 0, so we allocate all percpu areas on node 0.

This is visible in the dmesg output, as all pcpu allocs being in group 0:

  pcpu-alloc: [0] 00 01 02 03 [0] 04 05 06 07
  pcpu-alloc: [0] 08 09 10 11 [0] 12 13 14 15
  pcpu-alloc: [0] 16 17 18 19 [0] 20 21 22 23
  pcpu-alloc: [0] 24 25 26 27 [0] 28 29 30 31
  pcpu-alloc: [0] 32 33 34 35 [0] 36 37 38 39
  pcpu-alloc: [0] 40 41 42 43 [0] 44 45 46 47

To fix it we need an early_cpu_to_node() which can run prior to percpu being
setup. We already have the numa_cpu_lookup_table we can use, so just plumb it
in. With the patch dmesg output shows two groups, 0 and 1:

  pcpu-alloc: [0] 00 01 02 03 [0] 04 05 06 07
  pcpu-alloc: [0] 08 09 10 11 [0] 12 13 14 15
  pcpu-alloc: [0] 16 17 18 19 [0] 20 21 22 23
  pcpu-alloc: [1] 24 25 26 27 [1] 28 29 30 31
  pcpu-alloc: [1] 32 33 34 35 [1] 36 37 38 39
  pcpu-alloc: [1] 40 41 42 43 [1] 44 45 46 47

We can also check the data_offset in the paca of various CPUs, with the fix we
see:

  CPU 0:  data_offset = 0x0ffe8b0000
  CPU 24: data_offset = 0x1ffe5b0000

And we can see from dmesg that CPU 24 has an allocation on node 1:

  node   0: [mem 0x0000000000000000-0x0000000fffffffff]
  node   1: [mem 0x0000001000000000-0x0000001fffffffff]

Fixes: 8c272261194d ("powerpc/numa: Enable USE_PERCPU_NUMA_NODE_ID")
Signed-off-by: Michael Ellerman 
Reviewed-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/eeh: Avoid use after free in eeh_handle_special_event()

2017-06-14T11:16:25+00:00

commit daeba2956f32f91f3493788ff6ee02fb1b2f02fa upstream.

eeh_handle_special_event() is called when an EEH event is detected but
can't be narrowed down to a specific PE.  This function looks through
every PE to find one in an erroneous state, then calls the regular event
handler eeh_handle_normal_event() once it knows which PE has an error.

However, if eeh_handle_normal_event() found that the PE cannot possibly
be recovered, it will free it, rendering the passed PE stale.
This leads to a use after free in eeh_handle_special_event() as it attempts to
clear the "recovering" state on the PE after eeh_handle_normal_event() returns.

Thus, make sure the PE is valid when attempting to clear state in
eeh_handle_special_event().

Fixes: 8a6b1bc70dbb ("powerpc/eeh: EEH core to handle special event")
Reported-by: Alexey Kardashevskiy 
Signed-off-by: Russell Currey 
Reviewed-by: Gavin Shan 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/64e: Fix hang when debugging programs with relocated kernel

2017-05-25T12:30:15+00:00

commit fd615f69a18a9d4aa5ef02a1dc83f319f75da8e7 upstream.

Debug interrupts can be taken during interrupt entry, since interrupt
entry does not automatically turn them off.  The kernel will check
whether the faulting instruction is between [interrupt_base_book3e,
__end_interrupts], and if so clear MSR[DE] and return.

However, when the kernel is built with CONFIG_RELOCATABLE, it can't use
LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e) and
LOAD_REG_IMMEDIATE(r15,__end_interrupts), as they ignore relocation.
Thus, if the kernel is actually running at a different address than it
was built at, the address comparison will fail, and the exception entry
code will hang at kernel_dbg_exc.

r2(toc) is also not usable here, as r2 still holds data from the
interrupted context, so LOAD_REG_ADDR() doesn't work either.  So we use
the *name@got* to get the EV of two labels directly.

Test programs test.c shows as follows:
int main(int argc, char *argv[])
{
	if (access("/proc/sys/kernel/perf_event_paranoid", F_OK) == -1)
		printf("Kernel doesn't have perf_event support\n");
}

Steps to reproduce the bug, for example:
 1) ./gdb ./test
 2) (gdb) b access
 3) (gdb) r
 4) (gdb) s

Signed-off-by: Liu Hailong 
Signed-off-by: Jiang Xuexin 
Reviewed-by: Jiang Biao 
Reviewed-by: Liu Song 
Reviewed-by: Huang Jian 
[scottwood: cleaned up commit message, and specified bad behavior
 as a hang rather than an oops to correspond to mainline kernel behavior]
Fixes: 1cb6e0649248 ("powerpc/book3e: support CONFIG_RELOCATABLE")
Signed-off-by: Scott Wood 
Signed-off-by: Greg Kroah-Hartman

powerpc/pseries: Fix of_node_put() underflow during DLPAR remove

2017-05-25T12:30:15+00:00

commit 68baf692c435339e6295cb470ea5545cbc28160e upstream.

Historically struct device_node references were tracked using a kref embedded as
a struct field. Commit 75b57ecf9d1d ("of: Make device nodes kobjects so they
show up in sysfs") (Mar 2014) refactored device_nodes to be kobjects such that
the device tree could by more simply exposed to userspace using sysfs.

Commit 0829f6d1f69e ("of: device_node kobject lifecycle fixes") (Mar 2014)
followed up these changes to better control the kobject lifecycle and in
particular the referecne counting via of_node_get(), of_node_put(), and
of_node_init().

A result of this second commit was that it introduced an of_node_put() call when
a dynamic node is detached, in of_node_remove(), that removes the initial kobj
reference created by of_node_init().

Traditionally as the original dynamic device node user the pseries code had
assumed responsibilty for releasing this final reference in its platform
specific DLPAR detach code.

This patch fixes a refcount underflow introduced by commit 0829f6d1f6, and
recently exposed by the upstreaming of the recount API.

Messages like the following are no longer seen in the kernel log with this
patch following DLPAR remove operations of cpus and pci devices.

  rpadlpar_io: slot PHB 72 removed
  refcount_t: underflow; use-after-free.
  ------------[ cut here ]------------
  WARNING: CPU: 5 PID: 3335 at lib/refcount.c:128 refcount_sub_and_test+0xf4/0x110

Fixes: 0829f6d1f69e ("of: device_node kobject lifecycle fixes")
Signed-off-by: Tyrel Datwyler 
[mpe: Make change log commit references more verbose]
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman