linux-stable.git/kernel, branch v3.16.54

x86: pvclock: Really remove the sched notifier for cross-cpu migrations

2018-02-13T18:42:34+00:00

commit 73459e2a1ada09a68c02cc5b73f3116fc8194b3d upstream.

This reverts commits 0a4e6be9ca17c54817cf814b4b5aa60478c6df27
and 80f7fdb1c7f0f9266421f823964fd1962681f6ce.

The task migration notifier was originally introduced in order to support
the pvclock vsyscall with non-synchronized TSC, but KVM only supports it
with synchronized TSC.  Hence, on KVM the race condition is only needed
due to a bad implementation on the host side, and even then it's so rare
that it's mostly theoretical.

As far as KVM is concerned it's possible to fix the host, avoiding the
additional complexity in the vDSO and the (re)introduction of the task
migration notifier.

Xen, on the other hand, hasn't yet implemented vsyscall support at
all, so we do not care about its plans for non-synchronized TSC.

Reported-by: Peter Zijlstra 
Suggested-by: Marcelo Tosatti 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Ben Hutchings

blktrace: fix unlocked access to init/start-stop/teardown

2018-02-13T18:42:21+00:00

commit 1f2cac107c591c24b60b115d6050adc213d10fc0 upstream.

sg.c calls into the blktrace functions without holding the proper queue
mutex for doing setup, start/stop, or teardown.

Add internal unlocked variants, and export the ones that do the proper
locking.

Fixes: 6da127ad0918 ("blktrace: Add blktrace ioctls to SCSI generic devices")
Tested-by: Dmitry Vyukov 
Signed-off-by: Jens Axboe 
Signed-off-by: Ben Hutchings

blktrace: Fix potential deadlock between delete & sysfs ops

2018-02-13T18:42:21+00:00

commit 5acb3cc2c2e9d3020a4fee43763c6463767f1572 upstream.

The lockdep code had reported the following unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(s_active#228);
                               lock(&bdev->bd_mutex/1);
                               lock(s_active#228);
  lock(&bdev->bd_mutex);

 *** DEADLOCK ***

The deadlock may happen when one task (CPU1) is trying to delete a
partition in a block device and another task (CPU0) is accessing
tracing sysfs file (e.g. /sys/block/dm-1/trace/act_mask) in that
partition.

The s_active isn't an actual lock. It is a reference count (kn->count)
on the sysfs (kernfs) file. Removal of a sysfs file, however, require
a wait until all the references are gone. The reference count is
treated like a rwsem using lockdep instrumentation code.

The fact that a thread is in the sysfs callback method or in the
ioctl call means there is a reference to the opended sysfs or device
file. That should prevent the underlying block structure from being
removed.

Instead of using bd_mutex in the block_device structure, a new
blk_trace_mutex is now added to the request_queue structure to protect
access to the blk_trace structure.

Suggested-by: Christoph Hellwig 
Signed-off-by: Waiman Long 
Acked-by: Steven Rostedt (VMware) 

Fix typo in patch subject line, and prune a comment detailing how
the code used to work.

Signed-off-by: Jens Axboe 
Signed-off-by: Ben Hutchings

kprobes, x86/alternatives: Use text_mutex to protect smp_alt_modules

2018-02-13T18:42:17+00:00

commit e846d13958066828a9483d862cc8370a72fadbb6 upstream.

We use alternatives_text_reserved() to check if the address is in
the fixed pieces of alternative reserved, but the problem is that
we don't hold the smp_alt mutex when call this function. So the list
traversal may encounter a deleted list_head if another path is doing
alternatives_smp_module_del().

One solution is that we can hold smp_alt mutex before call this
function, but the difficult point is that the callers of this
functions, arch_prepare_kprobe() and arch_prepare_optimized_kprobe(),
are called inside the text_mutex. So we must hold smp_alt mutex
before we go into these arch dependent code. But we can't now,
the smp_alt mutex is the arch dependent part, only x86 has it.
Maybe we can export another arch dependent callback to solve this.

But there is a simpler way to handle this problem. We can reuse the
text_mutex to protect smp_alt_modules instead of using another mutex.
And all the arch dependent checks of kprobes are inside the text_mutex,
so it's safe now.

Signed-off-by: Zhou Chengming 
Reviewed-by: Masami Hiramatsu 
Acked-by: Steven Rostedt (VMware) 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bp@suse.de
Fixes: 2cfa197 "ftrace/alternatives: Introducing *_text_reserved functions"
Link: http://lkml.kernel.org/r/1509585501-79466-1-git-send-email-zhouchengming1@huawei.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Ben Hutchings

KAISER: Kernel Address Isolation

2018-01-09T00:35:13+00:00

This patch introduces our implementation of KAISER (Kernel Address Isolation to
have Side-channels Efficiently Removed), a kernel isolation technique to close
hardware side channels on kernel address information.

More information about the patch can be found on:

        https://github.com/IAIK/KAISER

From: Richard Fellner 
From: Daniel Gruss 
Subject: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode
Date: Thu, 4 May 2017 14:26:50 +0200
Link: http://marc.info/?l=linux-kernel&m=149390087310405&w=2
Kaiser-4.10-SHA1: c4b1831d44c6144d3762ccc72f0c4e71a0c713e5

To: 
To: 
Cc: 
Cc: 
Cc: Michael Schwarz 
Cc: Richard Fellner 
Cc: Ingo Molnar 
Cc: 
Cc: 

After several recent works [1,2,3] KASLR on x86_64 was basically
considered dead by many researchers. We have been working on an
efficient but effective fix for this problem and found that not mapping
the kernel space when running in user mode is the solution to this
problem [4] (the corresponding paper [5] will be presented at ESSoS17).

With this RFC patch we allow anybody to configure their kernel with the
flag CONFIG_KAISER to add our defense mechanism.

If there are any questions we would love to answer them.
We also appreciate any comments!

Cheers,
Daniel (+ the KAISER team from Graz University of Technology)

[1] http://www.ieee-security.org/TC/SP2013/papers/4977a191.pdf
[2] https://www.blackhat.com/docs/us-16/materials/us-16-Fogh-Using-Undocumented-CPU-Behaviour-To-See-Into-Kernel-Mode-And-Break-KASLR-In-The-Process.pdf
[3] https://www.blackhat.com/docs/us-16/materials/us-16-Jang-Breaking-Kernel-Address-Space-Layout-Randomization-KASLR-With-Intel-TSX.pdf
[4] https://github.com/IAIK/KAISER
[5] https://gruss.cc/files/kaiser.pdf

(cherry picked from Change-Id: I0eb000c33290af01fc4454ca0c701d00f1d30b1d)

Conflicts:
arch/x86/entry/entry_64.S (not in this tree)
arch/x86/kernel/entry_64.S (patched instead of that)
arch/x86/entry/entry_64_compat.S (not in this tree)
arch/x86/ia32/ia32entry.S (patched instead of that)
arch/x86/include/asm/hw_irq.h
arch/x86/include/asm/pgtable_types.h
arch/x86/include/asm/processor.h
arch/x86/kernel/irqinit.c
arch/x86/kernel/process.c
arch/x86/mm/Makefile
arch/x86/mm/pgtable.c
init/main.c

Signed-off-by: Hugh Dickins 
[bwh: Folded in the follow-up patches from Hugh:
 - kaiser: merged update
 - kaiser: do not set _PAGE_NX on pgd_none
 - kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE
 - kaiser: fix build and FIXME in alloc_ldt_struct()
 - kaiser: KAISER depends on SMP
 - kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER
 - kaiser: fix perf crashes
 - kaiser: ENOMEM if kaiser_pagetable_walk() NULL
 - kaiser: tidied up asm/kaiser.h somewhat
 - kaiser: tidied up kaiser_add/remove_mapping slightly
 - kaiser: kaiser_remove_mapping() move along the pgd
 - kaiser: align addition to x86/mm/Makefile
 - kaiser: cleanups while trying for gold link
 - kaiser: name that 0x1000 KAISER_SHADOW_PGD_OFFSET
 - kaiser: delete KAISER_REAL_SWITCH option
 - kaiser: vmstat show NR_KAISERTABLE as nr_overhead
 - kaiser: enhanced by kernel and user PCIDs
 - kaiser: load_new_mm_cr3() let SWITCH_USER_CR3 flush user
 - kaiser: PCID 0 for kernel and 128 for user
 - kaiser: x86_cr3_pcid_noflush and x86_cr3_pcid_user
 - kaiser: paranoid_entry pass cr3 need to paranoid_exit
 - kaiser: _pgd_alloc() without __GFP_REPEAT to avoid stalls
 - kaiser: fix unlikely error in alloc_ldt_struct()
 - kaiser: drop is_atomic arg to kaiser_pagetable_walk()
 Backported to 3.16:
 - Add missing #include in arch/x86/mm/kaiser.c
 - Use variable PEBS buffer size since we have "perf/x86/intel: Use PAGE_SIZE
   for PEBS buffer size on Core2"
 - Renumber X86_FEATURE_INVPCID_SINGLE to avoid collision
 - Adjust context]
Signed-off-by: Ben Hutchings

sched/core: Idle_task_exit() shouldn't use switch_mm_irqs_off()

2018-01-09T00:35:10+00:00

commit 252d2a4117bc181b287eeddf848863788da733ae upstream.

idle_task_exit() can be called with IRQs on x86 on and therefore
should use switch_mm(), not switch_mm_irqs_off().

This doesn't seem to cause any problems right now, but it will
confuse my upcoming TLB flush changes.  Nonetheless, I think it
should be backported because it's trivial.  There won't be any
meaningful performance impact because idle_task_exit() is only
used when offlining a CPU.

Signed-off-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: stable@vger.kernel.org
Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler")
Link: http://lkml.kernel.org/r/ca3d1a9fa93a0b49f5a8ff729eda3640fb6abdf9.1497034141.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Cc: Hugh Dickins 
Signed-off-by: Ben Hutchings

sched/core: Add switch_mm_irqs_off() and use it in the scheduler

2018-01-09T00:35:09+00:00

commit f98db6013c557c216da5038d9c52045be55cd039 upstream.

By default, this is the same thing as switch_mm().

x86 will override it as an optimization.

Signed-off-by: Andy Lutomirski 
Reviewed-by: Borislav Petkov 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/df401df47bdd6be3e389c6f1e3f5310d70e81b2c.1461688545.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Cc: Hugh Dickins 
Signed-off-by: Ben Hutchings

ptrace: Properly initialize ptracer_cred on fork

2018-01-01T20:52:11+00:00

commit c70d9d809fdeecedb96972457ee45c49a232d97f upstream.

When I introduced ptracer_cred I failed to consider the weirdness of
fork where the task_struct copies the old value by default.  This
winds up leaving ptracer_cred set even when a process forks and
the child process does not wind up being ptraced.

Because ptracer_cred is not set on non-ptraced processes whose
parents were ptraced this has broken the ability of the enlightenment
window manager to start setuid children.

Fix this by properly initializing ptracer_cred in ptrace_init_task

This must be done with a little bit of care to preserve the current value
of ptracer_cred when ptrace carries through fork.  Re-reading the
ptracer_cred from the ptracing process at this point is inconsistent
with how PT_PTRACE_CAP has been maintained all of these years.

Tested-by: Takashi Iwai 
Fixes: 64b875f7ac8a ("ptrace: Capture the ptracer's creds not PT_PTRACE_CAP")
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Ben Hutchings

ptrace: Don't allow accessing an undumpable mm

2018-01-01T20:52:11+00:00

commit 84d77d3f06e7e8dea057d10e8ec77ad71f721be3 upstream.

It is the reasonable expectation that if an executable file is not
readable there will be no way for a user without special privileges to
read the file.  This is enforced in ptrace_attach but if ptrace
is already attached before exec there is no enforcement for read-only
executables.

As the only way to read such an mm is through access_process_vm
spin a variant called ptrace_access_vm that will fail if the
target process is not being ptraced by the current process, or
the current process did not have sufficient privileges when ptracing
began to read the target processes mm.

In the ptrace implementations replace access_process_vm by
ptrace_access_vm.  There remain several ptrace sites that still use
access_process_vm as they are reading the target executables
instructions (for kernel consumption) or register stacks.  As such it
does not appear necessary to add a permission check to those calls.

This bug has always existed in Linux.

Fixes: v1.0
Reported-by: Andy Lutomirski 
Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.16:
 - Pass around only a write flag, not gup_flags
 - Adjust context]
Signed-off-by: Ben Hutchings

exec: Ensure mm->user_ns contains the execed files

2018-01-01T20:52:11+00:00

commit f84df2a6f268de584a201e8911384a2d244876e3 upstream.

When the user namespace support was merged the need to prevent
ptrace from revealing the contents of an unreadable executable
was overlooked.

Correct this oversight by ensuring that the executed file
or files are in mm->user_ns, by adjusting mm->user_ns.

Use the new function privileged_wrt_inode_uidgid to see if
the executable is a member of the user namespace, and as such
if having CAP_SYS_PTRACE in the user namespace should allow
tracing the executable.  If not update mm->user_ns to
the parent user namespace until an appropriate parent is found.

Reported-by: Jann Horn 
Fixes: 9e4a36ece652 ("userns: Fail exec for suid and sgid binaries with ids outside our user namespace.")
Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.16:
 - Add #include 
 - Adjust context]
Signed-off-by: Ben Hutchings