linux-stable.git/arch, branch v3.2.91

mm: Tighten x86 /dev/mem with zeroing reads

2017-07-18T17:38:44+00:00

commit a4866aa812518ed1a37d8ea0c881dc946409de94 upstream.

Under CONFIG_STRICT_DEVMEM, reading System RAM through /dev/mem is
disallowed. However, on x86, the first 1MB was always allowed for BIOS
and similar things, regardless of it actually being System RAM. It was
possible for heap to end up getting allocated in low 1MB RAM, and then
read by things like x86info or dd, which would trip hardened usercopy:

usercopy: kernel memory exposure attempt detected from ffff880000090000 (dma-kmalloc-256) (4096 bytes)

This changes the x86 exception for the low 1MB by reading back zeros for
System RAM areas instead of blindly allowing them. More work is needed to
extend this to mmap, but currently mmap doesn't go through usercopy, so
hardened usercopy won't Oops the kernel.

Reported-by: Tommi Rantala 
Tested-by: Tommi Rantala 
Signed-off-by: Kees Cook 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

x86/mm/init.c: Fix devmem_is_allowed() off by one

2017-07-18T17:38:44+00:00

commit 73e8f3d7e2cb23614d5115703d76d8e54764b641 upstream.

Fixing an off-by-one error in devmem_is_allowed(), which allows
accesses to physical addresses 0x100000-0x100fff, an extra page
past 1MB.

Signed-off-by: T Makphaibulchoke 
Acked-by: H. Peter Anvin 
Cc: yinghai@kernel.org
Cc: tiwai@suse.de
Cc: dhowells@redhat.com
Link: http://lkml.kernel.org/r/1346210503-14276-1-git-send-email-tmac@hp.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Ben Hutchings

ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram

2017-07-18T17:38:42+00:00

commit 34a477e5297cbaa6ecc6e17c042a866e1cbe80d6 upstream.

On x86-32, with CONFIG_FIRMWARE and multiple CPUs, if you enable function
graph tracing and then suspend to RAM, it will triple fault and reboot when
it resumes.

The first fault happens when booting a secondary CPU:

startup_32_smp()
  load_ucode_ap()
    prepare_ftrace_return()
      ftrace_graph_is_dead()
        (accesses 'kill_ftrace_graph')

The early head_32.S code calls into load_ucode_ap(), which has an an
ftrace hook, so it calls prepare_ftrace_return(), which calls
ftrace_graph_is_dead(), which tries to access the global
'kill_ftrace_graph' variable with a virtual address, causing a fault
because the CPU is still in real mode.

The fix is to add a check in prepare_ftrace_return() to make sure it's
running in protected mode before continuing.  The check makes sure the
stack pointer is a virtual kernel address.  It's a bit of a hack, but
it's not very intrusive and it works well enough.

For reference, here are a few other (more difficult) ways this could
have potentially been fixed:

- Move startup_32_smp()'s call to load_ucode_ap() down to *after* paging
  is enabled.  (No idea what that would break.)

- Track down load_ucode_ap()'s entire callee tree and mark all the
  functions 'notrace'.  (Probably not realistic.)

- Pause graph tracing in ftrace_suspend_notifier_call() or bringup_cpu()
  or __cpu_up(), and ensure that the pause facility can be queried from
  real mode.

Reported-by: Paul Menzel 
Signed-off-by: Josh Poimboeuf 
Tested-by: Paul Menzel 
Reviewed-by: Steven Rostedt (VMware) 
Cc: "Rafael J . Wysocki" 
Cc: linux-acpi@vger.kernel.org
Cc: Borislav Petkov 
Cc: Len Brown 
Link: http://lkml.kernel.org/r/5c1272269a580660703ed2eccf44308e790c7a98.1492123841.git.jpoimboe@redhat.com
Signed-off-by: Thomas Gleixner 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

MIPS: KGDB: Use kernel context for sleeping threads

2017-07-18T17:38:42+00:00

commit 162b270c664dca2e0944308e92f9fcc887151a72 upstream.

KGDB is a kernel debug stub and it can't be used to debug userland as it
can only safely access kernel memory.

On MIPS however KGDB has always got the register state of sleeping
processes from the userland register context at the beginning of the
kernel stack. This is meaningless for kernel threads (which never enter
userland), and for user threads it prevents the user seeing what it is
doing while in the kernel:

(gdb) info threads
  Id   Target Id         Frame
  ...
  3    Thread 2 (kthreadd) 0x0000000000000000 in ?? ()
  2    Thread 1 (init)   0x000000007705c4b4 in ?? ()
  1    Thread -2 (shadowCPU0) 0xffffffff8012524c in arch_kgdb_breakpoint () at arch/mips/kernel/kgdb.c:201

Get the register state instead from the (partial) kernel register
context stored in the task's thread_struct for resume() to restore. All
threads now correctly appear to be in context_switch():

(gdb) info threads
  Id   Target Id         Frame
  ...
  3    Thread 2 (kthreadd) context_switch (rq=, cookie=..., next=, prev=0x0) at kernel/sched/core.c:2903
  2    Thread 1 (init)   context_switch (rq=, cookie=..., next=, prev=0x0) at kernel/sched/core.c:2903
  1    Thread -2 (shadowCPU0) 0xffffffff8012524c in arch_kgdb_breakpoint () at arch/mips/kernel/kgdb.c:201

Call clobbered registers which aren't saved and exception registers
(BadVAddr & Cause) which can't be easily determined without stack
unwinding are reported as 0. The PC is taken from the return address,
such that the state presented matches that found immediately after
returning from resume().

Fixes: 8854700115ec ("[MIPS] kgdb: add arch support for the kernel's kgdb core")
Signed-off-by: James Hogan 
Cc: Jason Wessel 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15829/
Signed-off-by: Ralf Baechle 
Signed-off-by: Ben Hutchings

x86/vdso: Plug race between mapping and ELF header setup

2017-07-18T17:38:42+00:00

commit 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 upstream.

The vsyscall32 sysctl can racy against a concurrent fork when it switches
from disabled to enabled:

    arch_setup_additional_pages()
	if (vdso32_enabled)
           --> No mapping
                                        sysctl.vsysscall32()
                                          --> vdso32_enabled = true
    create_elf_tables()
      ARCH_DLINFO_IA32
        if (vdso32_enabled) {
           --> Add VDSO entry with NULL pointer

Make ARCH_DLINFO_IA32 check whether the VDSO mapping has been set up for
the newly forked process or not.

Signed-off-by: Thomas Gleixner 
Acked-by: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: Mathias Krause 
Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de
Signed-off-by: Thomas Gleixner 
[bwh: Backported to 3.2: change the flag passed to ARCH_DLINFO_IA32()]
Signed-off-by: Ben Hutchings

powerpc: Don't try to fix up misaligned load-with-reservation instructions

2017-07-18T17:38:40+00:00

commit 48fe9e9488743eec9b7c1addd3c93f12f2123d54 upstream.

In the past, there was only one load-with-reservation instruction,
lwarx, and if a program attempted a lwarx on a misaligned address, it
would take an alignment interrupt and the kernel handler would emulate
it as though it was lwzx, which was not really correct, but benign since
it is loading the right amount of data, and the lwarx should be paired
with a stwcx. to the same address, which would also cause an alignment
interrupt which would result in a SIGBUS being delivered to the process.

We now have 5 different sizes of load-with-reservation instruction. Of
those, lharx and ldarx cause an immediate SIGBUS by luck since their
entries in aligninfo[] overlap instructions which were not fixed up, but
lqarx overlaps with lhz and will be emulated as such. lbarx can never
generate an alignment interrupt since it only operates on 1 byte.

To straighten this out and fix the lqarx case, this adds code to detect
the l[hwdq]arx instructions and return without fixing them up, resulting
in a SIGBUS being delivered to the process.

Signed-off-by: Paul Mackerras 
Signed-off-by: Michael Ellerman 
[bwh: Backported to 3.2: open-code get_xop()]
Signed-off-by: Ben Hutchings

s390/decompressor: fix initrd corruption caused by bss clear

2017-07-18T17:38:36+00:00

commit d82c0d12c92705ef468683c9b7a8298dd61ed191 upstream.

Reorder the operations in decompress_kernel() to ensure initrd is moved
to a safe location before the bss section is zeroed.

During decompression bss can overlap with the initrd and this can
corrupt the initrd contents depending on the size of the compressed
kernel (which affects where the initrd is placed by the bootloader) and
the size of the bss section of the decompressor.

Also use the correct initrd size when checking for overlaps with
parmblock.

Fixes: 06c0dd72aea3 ([S390] fix boot failures with compressed kernels)
Reviewed-by: Joy Latten 
Reviewed-by: Vineetha HariPai 
Signed-off-by: Marcelo Henrique Cerri 
Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Ben Hutchings

xen: do not re-use pirq number cached in pci device msi msg data

2017-07-18T17:38:29+00:00

commit c74fd80f2f41d05f350bb478151021f88551afe8 upstream.

Revert the main part of commit:
af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests")

That commit introduced reading the pci device's msi message data to see
if a pirq was previously configured for the device's msi/msix, and re-use
that pirq.  At the time, that was the correct behavior.  However, a
later change to Qemu caused it to call into the Xen hypervisor to unmap
all pirqs for a pci device, when the pci device disables its MSI/MSIX
vectors; specifically the Qemu commit:
c976437c7dba9c7444fb41df45468968aaa326ad
("qemu-xen: free all the pirqs for msi/msix when driver unload")

Once Qemu added this pirq unmapping, it was no longer correct for the
kernel to re-use the pirq number cached in the pci device msi message
data.  All Qemu releases since 2.1.0 contain the patch that unmaps the
pirqs when the pci device disables its MSI/MSIX vectors.

This bug is causing failures to initialize multiple NVMe controllers
under Xen, because the NVMe driver sets up a single MSIX vector for
each controller (concurrently), and then after using that to talk to
the controller for some configuration data, it disables the single MSIX
vector and re-configures all the MSIX vectors it needs.  So the MSIX
setup code tries to re-use the cached pirq from the first vector
for each controller, but the hypervisor has already given away that
pirq to another controller, and its initialization fails.

This is discussed in more detail at:
https://lists.xen.org/archives/html/xen-devel/2017-01/msg00447.html

Fixes: af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests")
Signed-off-by: Dan Streetman 
Reviewed-by: Stefano Stabellini 
Acked-by: Konrad Rzeszutek Wilk 
Signed-off-by: Boris Ostrovsky 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

mm: larger stack guard gap, between vmas

2017-07-02T16:12:47+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 
[Hugh Dickins: Backported to 3.2]
[bwh: Fix more instances of vma->vm_start in sparc64 impl. of
 arch_get_unmapped_area_topdown() and generic impl. of
 hugetlb_get_unmapped_area()]
Signed-off-by: Ben Hutchings

MIPS: ip27: Disable qlge driver in defconfig

2017-06-05T20:13:49+00:00

commit b617649468390713db1515ea79fc772d2eb897a8 upstream.

One of the last remaining failures in kernelci.org is for a gcc bug:

drivers/net/ethernet/qlogic/qlge/qlge_main.c:4819:1: error: insn does not satisfy its constraints:
drivers/net/ethernet/qlogic/qlge/qlge_main.c:4819:1: internal compiler error: in extract_constrain_insn, at recog.c:2190

This is apparently broken in gcc-6 but fixed in gcc-7, and I cannot
reproduce the problem here. However, it is clear that ip27_defconfig
does not actually need this driver as the platform has only PCI-X but
not PCIe, and the qlge adapter in turn is PCIe-only.

The driver was originally enabled in 2010 along with lots of other
drivers.

Fixes: 59d302b342e5 ("MIPS: IP27: Make defconfig useful again.")
Signed-off-by: Arnd Bergmann 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/15197/
Signed-off-by: James Hogan 
Signed-off-by: Ben Hutchings