linux.git/arch, branch v3.16.35

s390/mm: four page table levels vs. fork

2016-04-30T22:06:11+00:00

commit 3446c13b268af86391d06611327006b059b8bab1 upstream.

The fork of a process with four page table levels is broken since
git commit 6252d702c5311ce9 "[S390] dynamic page tables."

All new mm contexts are created with three page table levels and
an asce limit of 4TB. If the parent has four levels dup_mmap will
add vmas to the new context which are outside of the asce limit.
The subsequent call to copy_page_range will walk the three level
page table structure of the new process with non-zero pgd and pud
indexes. This leads to memory clobbers as the pgd_index *and* the
pud_index is added to the mm->pgd pointer without a pgd_deref
in between.

The init_new_context() function is selecting the number of page
table levels for a new context. The function is used by mm_init()
which in turn is called by dup_mm() and mm_alloc(). These two are
used by fork() and exec(). The init_new_context() function can
distinguish the two cases by looking at mm->context.asce_limit,
for fork() the mm struct has been copied and the number of page
table levels may not change. For exec() the mm_alloc() function
set the new mm structure to zero, in this case a three-level page
table is created as the temporary stack space is located at
STACK_TOP_MAX = 4TB.

This fixes CVE-2016-2143.

Reported-by: Marcin Kościelnicki 
Reviewed-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
[bwh: Backported to 3.16:
 - 31-bit s390 is still supported so keep the #ifdef CONFIG_64BIT conditions
 - PMDs are not accounted so don't call mm_inc_nr_pmds()
 - Adjust context]
Signed-off-by: Ben Hutchings

x86/mm/32: Enable full randomization on i386 and X86_32

2016-04-30T22:06:10+00:00

commit 8b8addf891de8a00e4d39fc32f93f7c5eb8feceb upstream.

Currently on i386 and on X86_64 when emulating X86_32 in legacy mode, only
the stack and the executable are randomized but not other mmapped files
(libraries, vDSO, etc.). This patch enables randomization for the
libraries, vDSO and mmap requests on i386 and in X86_32 in legacy mode.

By default on i386 there are 8 bits for the randomization of the libraries,
vDSO and mmaps which only uses 1MB of VA.

This patch preserves the original randomness, using 1MB of VA out of 3GB or
4GB. We think that 1MB out of 3GB is not a big cost for having the ASLR.

The first obvious security benefit is that all objects are randomized (not
only the stack and the executable) in legacy mode which highly increases
the ASLR effectiveness, otherwise the attackers may use these
non-randomized areas. But also sensitive setuid/setgid applications are
more secure because currently, attackers can disable the randomization of
these applications by setting the ulimit stack to "unlimited". This is a
very old and widely known trick to disable the ASLR in i386 which has been
allowed for too long.

Another trick used to disable the ASLR was to set the ADDR_NO_RANDOMIZE
personality flag, but fortunately this doesn't work on setuid/setgid
applications because there is security checks which clear Security-relevant
flags.

This patch always randomizes the mmap_legacy_base address, removing the
possibility to disable the ASLR by setting the stack to "unlimited".

Signed-off-by: Hector Marco-Gisbert 
Acked-by: Ismael Ripoll Ripoll 
Acked-by: Kees Cook 
Acked-by: Arjan van de Ven 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: akpm@linux-foundation.org
Cc: kees Cook 
Link: http://lkml.kernel.org/r/1457639460-5242-1-git-send-email-hecmargi@upv.es
Signed-off-by: Ingo Molnar 
Signed-off-by: Ben Hutchings

x86: standardize mmap_rnd() usage

2016-04-30T22:06:10+00:00

commit 82168140bc4cec7ec9bad39705518541149ff8b7 upstream.

In preparation for splitting out ET_DYN ASLR, this refactors the use of
mmap_rnd() to be used similarly to arm, and extracts the checking of
PF_RANDOMIZE.

Signed-off-by: Kees Cook 
Reviewed-by: Ingo Molnar 
Cc: Oleg Nesterov 
Cc: Andy Lutomirski 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

parisc: Unbreak handling exceptions from kernel modules

2016-04-30T22:06:10+00:00

commit 2ef4dfd9d9f288943e249b78365a69e3ea3ec072 upstream.

Handling exceptions from modules never worked on parisc.
It was just masked by the fact that exceptions from modules
don't happen during normal use.

When a module triggers an exception in get_user() we need to load the
main kernel dp value before accessing the exception_data structure, and
afterwards restore the original dp value of the module on exit.

Noticed-by: Mikulas Patocka 
Signed-off-by: Helge Deller 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

parisc: Fix kernel crash with reversed copy_from_user()

2016-04-30T22:06:10+00:00

commit ef72f3110d8b19f4c098a0bff7ed7d11945e70c6 upstream.

The kernel module testcase (lib/test_user_copy.c) exhibited a kernel
crash on parisc if the parameters for copy_from_user were reversed
("illegal reversed copy_to_user" testcase).

Fix this potential crash by checking the fault handler if the faulting
address is in the exception table.

Signed-off-by: Helge Deller 
Cc: Kees Cook 
Signed-off-by: Ben Hutchings

parisc: Avoid function pointers for kernel exception routines

2016-04-30T22:06:09+00:00

commit e3893027a300927049efc1572f852201eb785142 upstream.

We want to avoid the kernel module loader to create function pointers
for the kernel fixup routines of get_user() and put_user(). Changing
the external reference from function type to int type fixes this.

This unbreaks exception handling for get_user() and put_user() when
called from a kernel module.

Signed-off-by: Helge Deller 
Signed-off-by: Ben Hutchings

KVM: x86: Inject pending interrupt even if pending nmi exist

2016-04-30T22:06:08+00:00

commit 321c5658c5e9192dea0d58ab67cf1791e45b2b26 upstream.

Non maskable interrupts (NMI) are preferred to interrupts in current
implementation. If a NMI is pending and NMI is blocked by the result
of nmi_allowed(), pending interrupt is not injected and
enable_irq_window() is not executed, even if interrupts injection is
allowed.

In old kernel (e.g. 2.6.32), schedule() is often called in NMI context.
In this case, interrupts are needed to execute iret that intends end
of NMI. The flag of blocking new NMI is not cleared until the guest
execute the iret, and interrupts are blocked by pending NMI. Due to
this, iret can't be invoked in the guest, and the guest is starved
until block is cleared by some events (e.g. canceling injection).

This patch injects pending interrupts, when it's allowed, even if NMI
is blocked. And, If an interrupts is pending after executing
inject_pending_event(), enable_irq_window() is executed regardless of
NMI pending counter.

Signed-off-by: Yuki Shibuya 
Suggested-by: Paolo Bonzini 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Ben Hutchings

fs/coredump: prevent fsuid=0 dumps into user-controlled directories

2016-04-30T22:06:04+00:00

commit 378c6520e7d29280f400ef2ceaf155c86f05a71a upstream.

This commit fixes the following security hole affecting systems where
all of the following conditions are fulfilled:

 - The fs.suid_dumpable sysctl is set to 2.
 - The kernel.core_pattern sysctl's value starts with "/". (Systems
   where kernel.core_pattern starts with "|/" are not affected.)
 - Unprivileged user namespace creation is permitted. (This is
   true on Linux >=3.8, but some distributions disallow it by
   default using a distro patch.)

Under these conditions, if a program executes under secure exec rules,
causing it to run with the SUID_DUMP_ROOT flag, then unshares its user
namespace, changes its root directory and crashes, the coredump will be
written using fsuid=0 and a path derived from kernel.core_pattern - but
this path is interpreted relative to the root directory of the process,
allowing the attacker to control where a coredump will be written with
root privileges.

To fix the security issue, always interpret core_pattern for dumps that
are written under SUID_DUMP_ROOT relative to the root directory of init.

Signed-off-by: Jann Horn 
Acked-by: Kees Cook 
Cc: Al Viro 
Cc: "Eric W. Biederman" 
Cc: Andy Lutomirski 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

KVM: VMX: avoid guest hang on invalid invept instruction

2016-04-30T22:06:03+00:00

commit 2849eb4f99d54925c543db12917127f88b3c38ff upstream.

A guest executing an invalid invept instruction would hang
because the instruction pointer was not updated.

Fixes: bfd0a56b90005f8c8a004baf407ad90045c2b11e
Reviewed-by: David Matlack 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Ben Hutchings

x86/apic: Fix suspicious RCU usage in smp_trace_call_function_interrupt()

2016-04-30T22:06:01+00:00

commit 7834c10313fb823e538f2772be78edcdeed2e6e3 upstream.

Since 4.4, I've been able to trigger this occasionally:

===============================
[ INFO: suspicious RCU usage. ]
4.5.0-rc7-think+ #3 Not tainted
Cc: Andi Kleen 
Link: http://lkml.kernel.org/r/20160315012054.GA17765@codemonkey.org.uk
Signed-off-by: Thomas Gleixner 

-------------------------------
./arch/x86/include/asm/msr-trace.h:47 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 1
RCU used illegally from extended quiescent state!
no locks held by swapper/3/0.

stack backtrace:
CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.5.0-rc7-think+ #3
 ffffffff92f821e0 1f3e5c340597d7fc ffff880468e07f10 ffffffff92560c2a
 ffff880462145280 0000000000000001 ffff880468e07f40 ffffffff921376a6
 ffffffff93665ea0 0000cc7c876d28da 0000000000000005 ffffffff9383dd60
Call Trace:
   [] dump_stack+0x67/0x9d
 [] lockdep_rcu_suspicious+0xe6/0x100
 [] do_trace_write_msr+0x127/0x1a0
 [] native_apic_msr_eoi_write+0x23/0x30
 [] smp_trace_call_function_interrupt+0x38/0x360
 [] trace_call_function_interrupt+0x90/0xa0
   [] ? cpuidle_enter_state+0x1b4/0x520

Move the entering_irq() call before ack_APIC_irq(), because entering_irq()
tells the RCU susbstems to end the extended quiescent state, so that the
following trace call in ack_APIC_irq() works correctly.

Suggested-by: Andi Kleen 
Fixes: 4787c368a9bc "x86/tracing: Add irq_enter/exit() in smp_trace_reschedule_interrupt()"
Signed-off-by: Dave Jones 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Ben Hutchings