linux-stable.git/kernel, branch v5.4.55

uprobes: Change handle_swbp() to send SIGTRAP with si_code=SI_KERNEL, to fix GDB regression

2020-07-29T08:18:29+00:00

commit fe5ed7ab99c656bd2f5b79b49df0e9ebf2cead8a upstream.

If a tracee is uprobed and it hits int3 inserted by debugger, handle_swbp()
does send_sig(SIGTRAP, current, 0) which means si_code == SI_USER. This used
to work when this code was written, but then GDB started to validate si_code
and now it simply can't use breakpoints if the tracee has an active uprobe:

	# cat test.c
	void unused_func(void)
	{
	}
	int main(void)
	{
		return 0;
	}

	# gcc -g test.c -o test
	# perf probe -x ./test -a unused_func
	# perf record -e probe_test:unused_func gdb ./test -ex run
	GNU gdb (GDB) 10.0.50.20200714-git
	...
	Program received signal SIGTRAP, Trace/breakpoint trap.
	0x00007ffff7ddf909 in dl_main () from /lib64/ld-linux-x86-64.so.2
	(gdb)

The tracee hits the internal breakpoint inserted by GDB to monitor shared
library events but GDB misinterprets this SIGTRAP and reports a signal.

Change handle_swbp() to use force_sig(SIGTRAP), this matches do_int3_user()
and fixes the problem.

This is the minimal fix for -stable, arch/x86/kernel/uprobes.c is equally
wrong; it should use send_sigtrap(TRAP_TRACE) instead of send_sig(SIGTRAP),
but this doesn't confuse GDB and needs another x86-specific patch.

Reported-by: Aaron Merey 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Ingo Molnar 
Reviewed-by: Srikar Dronamraju 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200723154420.GA32043@redhat.com
Signed-off-by: Greg Kroah-Hartman

genirq/affinity: Handle affinity setting on inactive interrupts correctly

2020-07-22T07:33:16+00:00

commit baedb87d1b53532f81b4bd0387f83b05d4f7eb9a upstream.

Setting interrupt affinity on inactive interrupts is inconsistent when
hierarchical irq domains are enabled. The core code should just store the
affinity and not call into the irq chip driver for inactive interrupts
because the chip drivers may not be in a state to handle such requests.

X86 has a hacky workaround for that but all other irq chips have not which
causes problems e.g. on GIC V3 ITS.

Instead of adding more ugly hacks all over the place, solve the problem in
the core code. If the affinity is set on an inactive interrupt then:

    - Store it in the irq descriptors affinity mask
    - Update the effective affinity to reflect that so user space has
      a consistent view
    - Don't call into the irq chip driver

This is the core equivalent of the X86 workaround and works correctly
because the affinity setting is established in the irq chip when the
interrupt is activated later on.

Note, that this is only effective when hierarchical irq domains are enabled
by the architecture. Doing it unconditionally would break legacy irq chip
implementations.

For hierarchial irq domains this works correctly as none of the drivers can
have a dependency on affinity setting in inactive state by design.

Remove the X86 workaround as it is not longer required.

Fixes: 02edee152d6e ("x86/apic/vector: Ignore set_affinity call for inactive interrupts")
Reported-by: Ali Saidi 
Signed-off-by: Thomas Gleixner 
Tested-by: Ali Saidi 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200529015501.15771-1-alisaidi@amazon.com
Link: https://lkml.kernel.org/r/877dv2rv25.fsf@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman

sched/fair: handle case of task_h_load() returning 0

2020-07-22T07:33:16+00:00

commit 01cfcde9c26d8555f0e6e9aea9d6049f87683998 upstream.

task_h_load() can return 0 in some situations like running stress-ng
mmapfork, which forks thousands of threads, in a sched group on a 224 cores
system. The load balance doesn't handle this correctly because
env->imbalance never decreases and it will stop pulling tasks only after
reaching loop_max, which can be equal to the number of running tasks of
the cfs. Make sure that imbalance will be decreased by at least 1.

misfit task is the other feature that doesn't handle correctly such
situation although it's probably more difficult to face the problem
because of the smaller number of CPUs and running tasks on heterogenous
system.

We can't simply ensure that task_h_load() returns at least one because it
would imply to handle underflow in other places.

Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Valentin Schneider 
Reviewed-by: Dietmar Eggemann 
Tested-by: Dietmar Eggemann 
Cc:  # v4.4+
Link: https://lkml.kernel.org/r/20200710152426.16981-1-vincent.guittot@linaro.org
Signed-off-by: Greg Kroah-Hartman

sched: Fix unreliable rseq cpu_id for new tasks

2020-07-22T07:33:16+00:00

commit ce3614daabea8a2d01c1dd17ae41d1ec5e5ae7db upstream.

While integrating rseq into glibc and replacing glibc's sched_getcpu
implementation with rseq, glibc's tests discovered an issue with
incorrect __rseq_abi.cpu_id field value right after the first time
a newly created process issues sched_setaffinity.

For the records, it triggers after building glibc and running tests, and
then issuing:

  for x in {1..2000} ; do posix/tst-affinity-static  & done

and shows up as:

error: Unexpected CPU 2, expected 0
error: Unexpected CPU 2, expected 0
error: Unexpected CPU 2, expected 0
error: Unexpected CPU 2, expected 0
error: Unexpected CPU 138, expected 0
error: Unexpected CPU 138, expected 0
error: Unexpected CPU 138, expected 0
error: Unexpected CPU 138, expected 0

This is caused by the scheduler invoking __set_task_cpu() directly from
sched_fork() and wake_up_new_task(), thus bypassing rseq_migrate() which
is done by set_task_cpu().

Add the missing rseq_migrate() to both functions. The only other direct
use of __set_task_cpu() is done by init_idle(), which does not involve a
user-space task.

Based on my testing with the glibc test-case, just adding rseq_migrate()
to wake_up_new_task() is sufficient to fix the observed issue. Also add
it to sched_fork() to keep things consistent.

The reason why this never triggered so far with the rseq/basic_test
selftest is unclear.

The current use of sched_getcpu(3) does not typically require it to be
always accurate. However, use of the __rseq_abi.cpu_id field within rseq
critical sections requires it to be accurate. If it is not accurate, it
can cause corruption in the per-cpu data targeted by rseq critical
sections in user-space.

Reported-By: Florian Weimer 
Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-By: Florian Weimer 
Cc: stable@vger.kernel.org # v4.18+
Link: https://lkml.kernel.org/r/20200707201505.2632-1-mathieu.desnoyers@efficios.com
Signed-off-by: Greg Kroah-Hartman

timer: Fix wheel index calculation on last level

2020-07-22T07:33:14+00:00

commit e2a71bdea81690b6ef11f4368261ec6f5b6891aa upstream.

When an expiration delta falls into the last level of the wheel, that delta
has be compared against the maximum possible delay and reduced to fit in if
necessary.

However instead of comparing the delta against the maximum, the code
compares the actual expiry against the maximum. Then instead of fixing the
delta to fit in, it sets the maximum delta as the expiry value.

This can result in various undesired outcomes, the worst possible one
being a timer expiring 15 days ahead to fire immediately.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200717140551.29076-2-frederic@kernel.org
Signed-off-by: Greg Kroah-Hartman

timer: Prevent base->clk from moving backward

2020-07-22T07:33:13+00:00

commit 30c66fc30ee7a98c4f3adf5fb7e213b61884474f upstream.

When a timer is enqueued with a negative delta (ie: expiry is below
base->clk), it gets added to the wheel as expiring now (base->clk).

Yet the value that gets stored in base->next_expiry, while calling
trigger_dyntick_cpu(), is the initial timer->expires value. The
resulting state becomes:

	base->next_expiry < base->clk

On the next timer enqueue, forward_timer_base() may accidentally
rewind base->clk. As a possible outcome, timers may expire way too
early, the worst case being that the highest wheel levels get spuriously
processed again.

To prevent from that, make sure that base->next_expiry doesn't get below
base->clk.

Fixes: a683f390b93f ("timers: Forward the wheel clock whenever possible")
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Anna-Maria Behnsen 
Tested-by: Juri Lelli 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200703010657.2302-1-frederic@kernel.org
Signed-off-by: Greg Kroah-Hartman

cgroup: fix cgroup_sk_alloc() for sk_clone_lock()

2020-07-22T07:32:49+00:00

[ Upstream commit ad0f75e5f57ccbceec13274e1e242f2b5a6397ed ]

When we clone a socket in sk_clone_lock(), its sk_cgrp_data is
copied, so the cgroup refcnt must be taken too. And, unlike the
sk_alloc() path, sock_update_netprioidx() is not called here.
Therefore, it is safe and necessary to grab the cgroup refcnt
even when cgroup_sk_alloc is disabled.

sk_clone_lock() is in BH context anyway, the in_interrupt()
would terminate this function if called there. And for sk_alloc()
skcd->val is always zero. So it's safe to factor out the code
to make it more readable.

The global variable 'cgroup_sk_alloc_disabled' is used to determine
whether to take these reference counts. It is impossible to make
the reference counting correct unless we save this bit of information
in skcd->val. So, add a new bit there to record whether the socket
has already taken the reference counts. This obviously relies on
kmalloc() to align cgroup pointers to at least 4 bytes,
ARCH_KMALLOC_MINALIGN is certainly larger than that.

This bug seems to be introduced since the beginning, commit
d979a39d7242 ("cgroup: duplicate cgroup reference when cloning sockets")
tried to fix it but not compeletely. It seems not easy to trigger until
the recent commit 090e28b229af
("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged.

Fixes: bd1060a1d671 ("sock, cgroup: add sock->sk_cgroup")
Reported-by: Cameron Berkenpas 
Reported-by: Peter Geis 
Reported-by: Lu Fengqi 
Reported-by: Daniël Sonck 
Reported-by: Zhang Qiang 
Tested-by: Cameron Berkenpas 
Tested-by: Peter Geis 
Tested-by: Thomas Lamprecht 
Cc: Daniel Borkmann 
Cc: Zefan Li 
Cc: Tejun Heo 
Cc: Roman Gushchin 
Signed-off-by: Cong Wang 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

bpf: Check correct cred for CAP_SYSLOG in bpf_dump_raw_ok()

2020-07-16T06:16:45+00:00

commit 63960260457a02af2a6cb35d75e6bdb17299c882 upstream.

When evaluating access control over kallsyms visibility, credentials at
open() time need to be used, not the "current" creds (though in BPF's
case, this has likely always been the same). Plumb access to associated
file->f_cred down through bpf_dump_raw_ok() and its callers now that
kallsysm_show_value() has been refactored to take struct cred.

Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: bpf@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: 7105e828c087 ("bpf: allow for correlation of maps and helpers in dump")
Signed-off-by: Kees Cook 
Signed-off-by: Greg Kroah-Hartman

kprobes: Do not expose probe addresses to non-CAP_SYSLOG

2020-07-16T06:16:45+00:00

commit 60f7bb66b88b649433bf700acfc60c3f24953871 upstream.

The kprobe show() functions were using "current"'s creds instead
of the file opener's creds for kallsyms visibility. Fix to use
seq_file->file->f_cred.

Cc: Masami Hiramatsu 
Cc: stable@vger.kernel.org
Fixes: 81365a947de4 ("kprobes: Show address of kprobes if kallsyms does")
Fixes: ffb9bd68ebdb ("kprobes: Show blacklist addresses as same as kallsyms does")
Signed-off-by: Kees Cook 
Signed-off-by: Greg Kroah-Hartman

module: Do not expose section addresses to non-CAP_SYSLOG

2020-07-16T06:16:45+00:00

commit b25a7c5af9051850d4f3d93ca500056ab6ec724b upstream.

The printing of section addresses in /sys/module/*/sections/* was not
using the correct credentials to evaluate visibility.

Before:

 # cat /sys/module/*/sections/.*text
 0xffffffffc0458000
 ...
 # capsh --drop=CAP_SYSLOG -- -c "cat /sys/module/*/sections/.*text"
 0xffffffffc0458000
 ...

After:

 # cat /sys/module/*/sections/*.text
 0xffffffffc0458000
 ...
 # capsh --drop=CAP_SYSLOG -- -c "cat /sys/module/*/sections/.*text"
 0x0000000000000000
 ...

Additionally replaces the existing (safe) /proc/modules check with
file->f_cred for consistency.

Reported-by: Dominik Czarnota 
Fixes: be71eda5383f ("module: Fix display of wrong module .text address")
Cc: stable@vger.kernel.org
Tested-by: Jessica Yu 
Acked-by: Jessica Yu 
Signed-off-by: Kees Cook 
Signed-off-by: Greg Kroah-Hartman