linux-toradex.git/kernel/events/core.c, branch v4.9.66

bpf: one perf event close won't free bpf program attached by another perf event

2017-10-12T09:51:21+00:00

[ Upstream commit ec9dd352d591f0c90402ec67a317c1ed4fb2e638 ]

This patch fixes a bug exhibited by the following scenario:
  1. fd1 = perf_event_open with attr.config = ID1
  2. attach bpf program prog1 to fd1
  3. fd2 = perf_event_open with attr.config = ID1
     
  4. user program closes fd2 and prog1 is detached from the tracepoint.
  5. user program with fd1 does not work properly as tracepoint
     no output any more.

The issue happens at step 4. Multiple perf_event_open can be called
successfully, but only one bpf prog pointer in the tp_event. In the
current logic, any fd release for the same tp_event will free
the tp_event->prog.

The fix is to free tp_event->prog only when the closing fd
corresponds to the one which registered the program.

Signed-off-by: Yonghong Song 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix group {cpu,task} validation

2017-08-30T08:21:50+00:00

commit 64aee2a965cf2954a038b5522f11d2cd2f0f8f3e upstream.

Regardless of which events form a group, it does not make sense for the
events to target different tasks and/or CPUs, as this leaves the group
inconsistent and impossible to schedule. The core perf code assumes that
these are consistent across (successfully intialised) groups.

Core perf code only verifies this when moving SW events into a HW
context. Thus, we can violate this requirement for pure SW groups and
pure HW groups, unless the relevant PMU driver happens to perform this
verification itself. These mismatched groups subsequently wreak havoc
elsewhere.

For example, we handle watchpoints as SW events, and reserve watchpoint
HW on a per-CPU basis at pmu::event_init() time to ensure that any event
that is initialised is guaranteed to have a slot at pmu::add() time.
However, the core code only checks the group leader's cpu filter (via
event_filter_match()), and can thus install follower events onto CPUs
violating thier (mismatched) CPU filters, potentially installing them
into a CPU without sufficient reserved slots.

This can be triggered with the below test case, resulting in warnings
from arch backends.

  #define _GNU_SOURCE
  #include 
  #include 
  #include 
  #include 
  #include 
  #include 
  #include 

  static int perf_event_open(struct perf_event_attr *attr, pid_t pid, int cpu,
			   int group_fd, unsigned long flags)
  {
	return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
  }

  char watched_char;

  struct perf_event_attr wp_attr = {
	.type = PERF_TYPE_BREAKPOINT,
	.bp_type = HW_BREAKPOINT_RW,
	.bp_addr = (unsigned long)&watched_char,
	.bp_len = 1,
	.size = sizeof(wp_attr),
  };

  int main(int argc, char *argv[])
  {
	int leader, ret;
	cpu_set_t cpus;

	/*
	 * Force use of CPU0 to ensure our CPU0-bound events get scheduled.
	 */
	CPU_ZERO(&cpus);
	CPU_SET(0, &cpus);
	ret = sched_setaffinity(0, sizeof(cpus), &cpus);
	if (ret) {
		printf("Unable to set cpu affinity\n");
		return 1;
	}

	/* open leader event, bound to this task, CPU0 only */
	leader = perf_event_open(&wp_attr, 0, 0, -1, 0);
	if (leader < 0) {
		printf("Couldn't open leader: %d\n", leader);
		return 1;
	}

	/*
	 * Open a follower event that is bound to the same task, but a
	 * different CPU. This means that the group should never be possible to
	 * schedule.
	 */
	ret = perf_event_open(&wp_attr, 0, 1, leader, 0);
	if (ret < 0) {
		printf("Couldn't open mismatched follower: %d\n", ret);
		return 1;
	} else {
		printf("Opened leader/follower with mismastched CPUs\n");
	}

	/*
	 * Open as many independent events as we can, all bound to the same
	 * task, CPU0 only.
	 */
	do {
		ret = perf_event_open(&wp_attr, 0, 0, -1, 0);
	} while (ret >= 0);

	/*
	 * Force enable/disble all events to trigger the erronoeous
	 * installation of the follower event.
	 */
	printf("Opened all events. Toggling..\n");
	for (;;) {
		prctl(PR_TASK_PERF_EVENTS_DISABLE, 0, 0, 0, 0);
		prctl(PR_TASK_PERF_EVENTS_ENABLE, 0, 0, 0, 0);
	}

	return 0;
  }

Fix this by validating this requirement regardless of whether we're
moving events.

Signed-off-by: Mark Rutland 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Zhou Chengming 
Link: http://lkml.kernel.org/r/1498142498-15758-1-git-send-email-mark.rutland@arm.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

Revert "perf/core: Drop kernel samples even though :u is specified"

2017-07-27T22:08:06+00:00

commit 6a8a75f3235724c5941a33e287b2f98966ad14c5 upstream.

This reverts commit cc1582c231ea041fbc68861dfaf957eaf902b829.

This commit introduced a regression that broke rr-project, which uses sampling
events to receive a signal on overflow (but does not care about the contents
of the sample). These signals are critical to the correct operation of rr.

There's been some back and forth about how to fix it - but to not keep
applications in limbo queue up a revert.

Reported-by: Kyle Huey 
Acked-by: Kyle Huey 
Acked-by: Peter Zijlstra 
Cc: Jin Yao 
Cc: Vince Weaver 
Cc: Linus Torvalds 
Cc: Will Deacon 
Cc: Arnaldo Carvalho de Melo 
Cc: Alexander Shishkin 
Cc: Stephane Eranian 
Cc: Namhyung Kim 
Cc: Jiri Olsa 
Link: http://lkml.kernel.org/r/20170628105600.GC5981@leverpostej
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix sys_perf_event_open() vs. hotplug

2017-07-05T12:40:26+00:00

[ Upstream commit 63cae12bce9861cec309798d34701cf3da20bc71 ]

There is problem with installing an event in a task that is 'stuck' on
an offline CPU.

Blocked tasks are not dis-assosciated from offlined CPUs, after all, a
blocked task doesn't run and doesn't require a CPU etc.. Only on
wakeup do we ammend the situation and place the task on a available
CPU.

If we hit such a task with perf_install_in_context() we'll loop until
either that task wakes up or the CPU comes back online, if the task
waking depends on the event being installed, we're stuck.

While looking into this issue, I also spotted another problem, if we
hit a task with perf_install_in_context() that is in the middle of
being migrated, that is we observe the old CPU before sending the IPI,
but run the IPI (on the old CPU) while the task is already running on
the new CPU, things also go sideways.

Rework things to rely on task_curr() -- outside of rq->lock -- which
is rather tricky. Imagine the following scenario where we're trying to
install the first event into our task 't':

CPU0            CPU1            CPU2

                (current == t)

t->perf_event_ctxp[] = ctx;
smp_mb();
cpu = task_cpu(t);

                switch(t, n);
                                migrate(t, 2);
                                switch(p, t);

                                ctx = t->perf_event_ctxp[]; // must not be NULL

smp_function_call(cpu, ..);

                generic_exec_single()
                  func();
                    spin_lock(ctx->lock);
                    if (task_curr(t)) // false

                    add_event_to_ctx();
                    spin_unlock(ctx->lock);

                                perf_event_context_sched_in();
                                  spin_lock(ctx->lock);
                                  // sees event

So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'.
Because if CPU2's load of that variable were to observe NULL, it would
not try to schedule the ctx and we'd have a task running without its
counter, which would be 'bad'.

As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it
first and not see the event yet, then CPU0 must observe task_curr()
and retry. If the install happens first, then we must see the event on
sched-in and all is well.

I think we can translate the first part (until the 'must not be NULL')
of the scenario to a litmus test like:

  C C-peterz

  {
  }

  P0(int *x, int *y)
  {
          int r1;

          WRITE_ONCE(*x, 1);
          smp_mb();
          r1 = READ_ONCE(*y);
  }

  P1(int *y, int *z)
  {
          WRITE_ONCE(*y, 1);
          smp_store_release(z, 1);
  }

  P2(int *x, int *z)
  {
          int r1;
          int r2;

          r1 = smp_load_acquire(z);
	  smp_mb();
          r2 = READ_ONCE(*x);
  }

  exists
  (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)

Where:
  x is perf_event_ctxp[],
  y is our tasks's CPU, and
  z is our task being placed on the rq of CPU2.

The P0 smp_mb() is the one added by this patch, ordering the store to
perf_event_ctxp[] from find_get_context() and the load of task_cpu()
in task_function_call().

The smp_store_release/smp_load_acquire model the RCpc locking of the
rq->lock and the smp_mb() of P2 is the context switch switching from
whatever CPU2 was running to our task 't'.

This litmus test evaluates into:

  Test C-peterz Allowed
  States 7
  0:r1=0; 2:r1=0; 2:r2=0;
  0:r1=0; 2:r1=0; 2:r2=1;
  0:r1=0; 2:r1=1; 2:r2=1;
  0:r1=1; 2:r1=0; 2:r2=0;
  0:r1=1; 2:r1=0; 2:r2=1;
  0:r1=1; 2:r1=1; 2:r2=0;
  0:r1=1; 2:r1=1; 2:r2=1;
  No
  Witnesses
  Positive: 0 Negative: 7
  Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
  Observation C-peterz Never 0 7
  Hash=e427f41d9146b2a5445101d3e2fcaa34

And the strong and weak model agree.

Reported-by: Mark Rutland 
Tested-by: Mark Rutland 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sebastian Andrzej Siewior 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: Will Deacon 
Cc: jeremy.linton@arm.com
Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

perf/core: Drop kernel samples even though :u is specified

2017-06-14T13:06:03+00:00

commit cc1582c231ea041fbc68861dfaf957eaf902b829 upstream.

When doing sampling, for example:

  perf record -e cycles:u ...

On workloads that do a lot of kernel entry/exits we see kernel
samples, even though :u is specified. This is due to skid existing.

This might be a security issue because it can leak kernel addresses even
though kernel sampling support is disabled.

The patch drops the kernel samples if exclude_kernel is specified.

For example, test on Haswell desktop:

  perf record -e cycles:u 
  perf report --stdio

Before patch applied:

    99.77%  mgen     mgen              [.] buf_read
     0.20%  mgen     mgen              [.] rand_buf_init
     0.01%  mgen     [kernel.vmlinux]  [k] apic_timer_interrupt
     0.00%  mgen     mgen              [.] last_free_elem
     0.00%  mgen     libc-2.23.so      [.] __random_r
     0.00%  mgen     libc-2.23.so      [.] _int_malloc
     0.00%  mgen     mgen              [.] rand_array_init
     0.00%  mgen     [kernel.vmlinux]  [k] page_fault
     0.00%  mgen     libc-2.23.so      [.] __random
     0.00%  mgen     libc-2.23.so      [.] __strcasestr
     0.00%  mgen     ld-2.23.so        [.] strcmp
     0.00%  mgen     ld-2.23.so        [.] _dl_start
     0.00%  mgen     libc-2.23.so      [.] sched_setaffinity@@GLIBC_2.3.4
     0.00%  mgen     ld-2.23.so        [.] _start

We can see kernel symbols apic_timer_interrupt and page_fault.

After patch applied:

    99.79%  mgen     mgen           [.] buf_read
     0.19%  mgen     mgen           [.] rand_buf_init
     0.00%  mgen     libc-2.23.so   [.] __random_r
     0.00%  mgen     mgen           [.] rand_array_init
     0.00%  mgen     mgen           [.] last_free_elem
     0.00%  mgen     libc-2.23.so   [.] vfprintf
     0.00%  mgen     libc-2.23.so   [.] rand
     0.00%  mgen     libc-2.23.so   [.] __random
     0.00%  mgen     libc-2.23.so   [.] _int_malloc
     0.00%  mgen     libc-2.23.so   [.] _IO_doallocbuf
     0.00%  mgen     ld-2.23.so     [.] do_lookup_x
     0.00%  mgen     ld-2.23.so     [.] open_verify.constprop.7
     0.00%  mgen     ld-2.23.so     [.] _dl_important_hwcaps
     0.00%  mgen     libc-2.23.so   [.] sched_setaffinity@@GLIBC_2.3.4
     0.00%  mgen     ld-2.23.so     [.] _start

There are only userspace symbols.

Signed-off-by: Jin Yao 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: acme@kernel.org
Cc: jolsa@kernel.org
Cc: kan.liang@intel.com
Cc: mark.rutland@arm.com
Cc: will.deacon@arm.com
Cc: yao.jin@intel.com
Link: http://lkml.kernel.org/r/1495706947-3744-1-git-send-email-yao.jin@linux.intel.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix event inheritance on fork()

2017-03-26T11:05:57+00:00

commit e7cc4865f0f31698ef2f7aac01a50e78968985b7 upstream.

While hunting for clues to a use-after-free, Oleg spotted that
perf_event_init_context() can loose an error value with the result
that fork() can succeed even though we did not fully inherit the perf
event context.

Spotted-by: Oleg Nesterov 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Dmitry Vyukov 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: oleg@redhat.com
Fixes: 889ff0150661 ("perf/core: Split context's event group list into pinned and non-pinned lists")
Link: http://lkml.kernel.org/r/20170316125823.190342547@infradead.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix use-after-free in perf_release()

2017-03-26T11:05:57+00:00

commit e552a8389aa409e257b7dcba74f67f128f979ccc upstream.

Dmitry reported syzcaller tripped a use-after-free in perf_release().

After much puzzlement Oleg spotted the below scenario:

  Task1                           Task2

  fork()
    perf_event_init_task()
    /* ... */
    goto bad_fork_$foo;
    /* ... */
    perf_event_free_task()
      mutex_lock(ctx->lock)
      perf_free_event(B)

                                  perf_event_release_kernel(A)
                                    mutex_lock(A->child_mutex)
                                    list_for_each_entry(child, ...) {
                                      /* child == B */
                                      ctx = B->ctx;
                                      get_ctx(ctx);
                                      mutex_unlock(A->child_mutex);

        mutex_lock(A->child_mutex)
        list_del_init(B->child_list)
        mutex_unlock(A->child_mutex)

        /* ... */

      mutex_unlock(ctx->lock);
      put_ctx() /* >0 */
    free_task();
                                      mutex_lock(ctx->lock);
                                      mutex_lock(A->child_mutex);
                                      /* ... */
                                      mutex_unlock(A->child_mutex);
                                      mutex_unlock(ctx->lock)
                                      put_ctx() /* 0 */
                                        ctx->task && !TOMBSTONE
                                          put_task_struct() /* UAF */

This patch closes the hole by making perf_event_free_task() destroy the
task <-> ctx relation such that perf_event_release_kernel() will no longer
observe the now dead task.

Spotted-by: Oleg Nesterov 
Reported-by: Dmitry Vyukov 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: fweisbec@gmail.com
Cc: oleg@redhat.com
Fixes: c6e5b73242d2 ("perf: Synchronously clean up child events")
Link: http://lkml.kernel.org/r/20170314155949.GE32474@worktop
Link: http://lkml.kernel.org/r/20170316125823.140295131@infradead.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix crash in perf_event_read()

2017-02-14T23:25:43+00:00

commit 451d24d1e5f40bad000fa9abe36ddb16fc9928cb upstream.

Alexei had his box explode because doing read() on a package
(rapl/uncore) event that isn't currently scheduled in ends up doing an
out-of-bounds load.

Rework the code to more explicitly deal with event->oncpu being -1.

Reported-by: Alexei Starovoitov 
Tested-by: Alexei Starovoitov 
Tested-by: David Carrillo-Cisneros 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: eranian@google.com
Fixes: d6a2f9035bfc ("perf/core: Introduce PMU_EV_CAP_READ_ACTIVE_PKG")
Link: http://lkml.kernel.org/r/20170131102710.GL6515@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix PERF_RECORD_MMAP2 prot/flags for anonymous memory

2017-02-09T07:08:26+00:00

commit 0b3589be9b98994ce3d5aeca52445d1f5627c4ba upstream.

Andres reported that MMAP2 records for anonymous memory always have
their protection field 0.

Turns out, someone daft put the prot/flags generation code in the file
branch, leaving them unset for anonymous memory.

Reported-by: Andres Freund 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Don Zickus 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: acme@kernel.org
Cc: anton@ozlabs.org
Cc: namhyung@kernel.org
Fixes: f972eb63b100 ("perf: Pass protection and flags bits through mmap2 interface")
Link: http://lkml.kernel.org/r/20170126221508.GF6536@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf/core: Fix use-after-free bug

2017-02-09T07:08:26+00:00

commit a76a82a3e38c8d3fb6499e3dfaeb0949241ab588 upstream.

Dmitry reported a KASAN use-after-free on event->group_leader.

It turns out there's a hole in perf_remove_from_context() due to
event_function_call() not calling its function when the task
associated with the event is already dead.

In this case the event will have been detached from the task, but the
grouping will have been retained, such that group operations might
still work properly while there are live child events etc.

This does however mean that we can miss a perf_group_detach() call
when the group decomposes, this in turn can then lead to
use-after-free.

Fix it by explicitly doing the group detach if its still required.

Reported-by: Dmitry Vyukov 
Tested-by: Dmitry Vyukov 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: syzkaller 
Fixes: 63b6da39bb38 ("perf: Fix perf_event_exit_task() race")
Link: http://lkml.kernel.org/r/20170126153955.GD6515@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman