linux-stable.git/kernel, branch v5.0.14

xdp: fix cpumap redirect SKB creation bug

2019-05-08T05:22:50+00:00

[ Upstream commit 676e4a6fe703f2dae699ee9d56f14516f9ada4ea ]

We want to avoid leaking pointer info from xdp_frame (that is placed in
top of frame) like commit 6dfb970d3dbd ("xdp: avoid leaking info stored in
frame data on page reuse"), and followup commit 97e19cce05e5 ("bpf:
reserve xdp_frame size in xdp headroom") that reserve this headroom.

These changes also affected how cpumap constructed SKBs, as xdpf->headroom
size changed, the skb data starting point were in-effect shifted with 32
bytes (sizeof xdp_frame). This was still okay, as the cpumap frame_size
calculation also included xdpf->headroom which were reduced by same amount.

A bug was introduced in commit 77ea5f4cbe20 ("bpf/cpumap: make sure
frame_size for build_skb is aligned if headroom isn't"), where the
xdpf->headroom became part of the SKB_DATA_ALIGN rounding up. This
round-up to find the frame_size is in principle still correct as it does
not exceed the 2048 bytes frame_size (which is max for ixgbe and i40e),
but the 32 bytes offset of pkt_data_start puts this over the 2048 bytes
limit. This cause skb_shared_info to spill into next frame. It is a little
hard to trigger, as the SKB need to use above 15 skb_shinfo->frags[] as
far as I calculate. This does happen in practise for TCP streams when
skb_try_coalesce() kicks in.

KASAN can be used to detect these wrong memory accesses, I've seen:
 BUG: KASAN: use-after-free in skb_try_coalesce+0x3cb/0x760
 BUG: KASAN: wild-memory-access in skb_release_data+0xe2/0x250

Driver veth also construct a SKB from xdp_frame in this way, but is not
affected, as it doesn't reserve/deduct the room (used by xdp_frame) from
the SKB headroom. Instead is clears the pointers via xdp_scrub_frame(),
and allows SKB to use this area.

The fix in this patch is to do like veth and instead allow SKB to (re)use
the area occupied by xdp_frame, by clearing via xdp_scrub_frame().  (This
does kill the idea of the SKB being able to access (mem) info from this
area, but I guess it was a bad idea anyhow, and it was already killed by
the veth changes.)

Fixes: 77ea5f4cbe20 ("bpf/cpumap: make sure frame_size for build_skb is aligned if headroom isn't")
Signed-off-by: Jesper Dangaard Brouer 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin (Microsoft)

seccomp: Make NEW_LISTENER and TSYNC flags exclusive

2019-05-08T05:22:42+00:00

commit 7a0df7fbc14505e2e2be19ed08654a09e1ed5bf6 upstream.

As the comment notes, the return codes for TSYNC and NEW_LISTENER
conflict, because they both return positive values, one in the case of
success and one in the case of error. So, let's disallow both of these
flags together.

While this is technically a userspace break, all the users I know
of are still waiting on me to land this feature in libseccomp, so I
think it'll be safe. Also, at present my use case doesn't require
TSYNC at all, so this isn't a big deal to disallow. If someone
wanted to support this, a path forward would be to add a new flag like
TSYNC_AND_LISTENER_YES_I_UNDERSTAND_THAT_TSYNC_WILL_JUST_RETURN_EAGAIN,
but the use cases are so different I don't see it really happening.

Finally, it's worth noting that this does actually fix a UAF issue: at the
end of seccomp_set_mode_filter(), we have:

        if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
                if (ret < 0) {
                        listener_f->private_data = NULL;
                        fput(listener_f);
                        put_unused_fd(listener);
                } else {
                        fd_install(listener, listener_f);
                        ret = listener;
                }
        }
out_free:
        seccomp_filter_free(prepared);

But if ret > 0 because TSYNC raced, we'll install the listener fd and then
free the filter out from underneath it, causing a UAF when the task closes
it or dies. This patch also switches the condition to be simply if (ret),
so that if someone does add the flag mentioned above, they won't have to
remember to fix this too.

Reported-by: syzbot+b562969adb2e04af3442@syzkaller.appspotmail.com
Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
CC: stable@vger.kernel.org # v5.0+
Signed-off-by: Tycho Andersen 
Signed-off-by: Kees Cook 
Acked-by: James Morris 
Signed-off-by: Greg Kroah-Hartman

ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK

2019-05-04T07:21:23+00:00

[ Upstream commit fcfc2aa0185f4a731d05a21e9f359968fdfd02e7 ]

There are a few system calls (pselect, ppoll, etc) which replace a task
sigmask while they are running in a kernel-space

When a task calls one of these syscalls, the kernel saves a current
sigmask in task->saved_sigmask and sets a syscall sigmask.

On syscall-exit-stop, ptrace traps a task before restoring the
saved_sigmask, so PTRACE_GETSIGMASK returns the syscall sigmask and
PTRACE_SETSIGMASK does nothing, because its sigmask is replaced by
saved_sigmask, when the task returns to user-space.

This patch fixes this problem.  PTRACE_GETSIGMASK returns saved_sigmask
if it's set.  PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.

Link: http://lkml.kernel.org/r/20181120060616.6043-1-avagin@gmail.com
Fixes: 29000caecbe8 ("ptrace: add ability to get/set signal-blocked mask")
Signed-off-by: Andrei Vagin 
Acked-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin (Microsoft)

fs: prevent page refcount overflow in pipe_buf_get

2019-05-04T07:21:11+00:00

commit 15fab63e1e57be9fdb5eec1bbc5916e9825e9acb upstream.

Change pipe_buf_get() to return a bool indicating whether it succeeded
in raising the refcount of the page (if the thing in the pipe is a page).
This removes another mechanism for overflowing the page refcount.  All
callers converted to handle a failure.

Reported-by: Jann Horn 
Signed-off-by: Matthew Wilcox 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sched/deadline: Correctly handle active 0-lag timers

2019-05-02T08:02:49+00:00

commit 1b02cd6a2d7f3e2a6a5262887d2cb2912083e42f upstream.

syzbot reported the following warning:

   [ ] WARNING: CPU: 4 PID: 17089 at kernel/sched/deadline.c:255 task_non_contending+0xae0/0x1950

line 255 of deadline.c is:

	WARN_ON(hrtimer_active(&dl_se->inactive_timer));

in task_non_contending().

Unfortunately, in some cases (for example, a deadline task
continuosly blocking and waking immediately) it can happen that
a task blocks (and task_non_contending() is called) while the
0-lag timer is still active.

In this case, the safest thing to do is to immediately decrease
the running bandwidth of the task, without trying to re-arm the 0-lag timer.

Signed-off-by: luca abeni 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Juri Lelli 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: chengjian (D) 
Link: https://lkml.kernel.org/r/20190325131530.34706-1-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

workqueue: Try to catch flush_work() without INIT_WORK().

2019-05-02T08:02:49+00:00

commit 4d43d395fed124631ca02356c711facb90185175 upstream.

syzbot found a flush_work() caller who forgot to call INIT_WORK()
because that work_struct was allocated by kzalloc() [1]. But the message

  INFO: trying to register non-static key.
  the code is fine but needs lockdep annotation.
  turning off the locking correctness validator.

by lock_map_acquire() is failing to tell that INIT_WORK() is missing.

Since flush_work() without INIT_WORK() is a bug, and INIT_WORK() should
set ->func field to non-zero, let's warn if ->func field is zero.

[1] https://syzkaller.appspot.com/bug?id=a5954455fcfa51c29ca2ab55b203076337e1c770

Signed-off-by: Tetsuo Handa 
Signed-off-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

sched/numa: Fix a possible divide-by-zero

2019-05-02T08:02:45+00:00

commit a860fa7b96e1a1c974556327aa1aee852d434c21 upstream.

sched_clock_cpu() may not be consistent between CPUs. If a task
migrates to another CPU, then se.exec_start is set to that CPU's
rq_clock_task() by update_stats_curr_start(). Specifically, the new
value might be before the old value due to clock skew.

So then if in numa_get_avg_runtime() the expression:

  'now - p->last_task_numa_placement'

ends up as -1, then the divider '*period + 1' in task_numa_placement()
is 0 and things go bang. Similar to update_curr(), check if time goes
backwards to avoid this.

[ peterz: Wrote new changelog. ]
[ mingo: Tweaked the code comment. ]

Signed-off-by: Xie XiuQi 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: cj.chengjian@huawei.com
Cc: 
Link: http://lkml.kernel.org/r/20190425080016.GX11158@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

trace: Fix preempt_enable_no_resched() abuse

2019-05-02T08:02:44+00:00

commit d6097c9e4454adf1f8f2c9547c2fa6060d55d952 upstream.

Unless the very next line is schedule(), or implies it, one must not use
preempt_enable_no_resched(). It can cause a preemption to go missing and
thereby cause arbitrary delays, breaking the PREEMPT=y invariant.

Link: http://lkml.kernel.org/r/20190423200318.GY14281@hirez.programming.kicks-ass.net

Cc: Waiman Long 
Cc: Linus Torvalds 
Cc: Ingo Molnar 
Cc: Will Deacon 
Cc: Thomas Gleixner 
Cc: the arch/x86 maintainers 
Cc: Davidlohr Bueso 
Cc: Tim Chen 
Cc: huang ying 
Cc: Roman Gushchin 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: stable@vger.kernel.org
Fixes: 2c2d7329d8af ("tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()")
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix buffer_ref pipe ops

2019-05-02T08:02:44+00:00

commit b987222654f84f7b4ca95b3a55eca784cb30235b upstream.

This fixes multiple issues in buffer_pipe_buf_ops:

 - The ->steal() handler must not return zero unless the pipe buffer has
   the only reference to the page. But generic_pipe_buf_steal() assumes
   that every reference to the pipe is tracked by the page's refcount,
   which isn't true for these buffers - buffer_pipe_buf_get(), which
   duplicates a buffer, doesn't touch the page's refcount.
   Fix it by using generic_pipe_buf_nosteal(), which refuses every
   attempted theft. It should be easy to actually support ->steal, but the
   only current users of pipe_buf_steal() are the virtio console and FUSE,
   and they also only use it as an optimization. So it's probably not worth
   the effort.
 - The ->get() and ->release() handlers can be invoked concurrently on pipe
   buffers backed by the same struct buffer_ref. Make them safe against
   concurrency by using refcount_t.
 - The pointers stored in ->private were only zeroed out when the last
   reference to the buffer_ref was dropped. As far as I know, this
   shouldn't be necessary anyway, but if we do it, let's always do it.

Link: http://lkml.kernel.org/r/20190404215925.253531-1-jannh@google.com

Cc: Ingo Molnar 
Cc: Masami Hiramatsu 
Cc: Al Viro 
Cc: stable@vger.kernel.org
Fixes: 73a757e63114d ("ring-buffer: Return reader page back into existing ring buffer")
Signed-off-by: Jann Horn 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix a memory leak by early error exit in trace_pid_write()

2019-05-02T08:02:43+00:00

commit 91862cc7867bba4ee5c8fcf0ca2f1d30427b6129 upstream.

In trace_pid_write(), the buffer for trace parser is allocated through
kmalloc() in trace_parser_get_init(). Later on, after the buffer is used,
it is then freed through kfree() in trace_parser_put(). However, it is
possible that trace_pid_write() is terminated due to unexpected errors,
e.g., ENOMEM. In that case, the allocated buffer will not be freed, which
is a memory leak bug.

To fix this issue, free the allocated buffer when an error is encountered.

Link: http://lkml.kernel.org/r/1555726979-15633-1-git-send-email-wang6495@umn.edu

Fixes: f4d34a87e9c10 ("tracing: Use pid bitmap instead of a pid array for set_event_pid")
Cc: stable@vger.kernel.org
Signed-off-by: Wenwen Wang 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman