Commit d670ec1317 "posix-cpu-timers: Cure SMP wobbles" fixes one glibc
test case in cost of breaking another one. After that commit, calling
clock_nanosleep(TIMER_ABSTIME, X) and then clock_gettime(&Y) can result
of Y time being smaller than X time.
Reproducer/tester can be found further below, it can be compiled and ran by:
gcc -o tst-cpuclock2 tst-cpuclock2.c -pthread
while ./tst-cpuclock2 ; do : ; done
This reproducer, when running on a buggy kernel, will complain
about "clock_gettime difference too small".
Issue happens because on start in thread_group_cputimer() we initialize
sum_exec_runtime of cputimer with threads runtime not yet accounted and
then add the threads runtime to running cputimer again on scheduler
tick, making it's sum_exec_runtime bigger than actual threads runtime.
KOSAKI Motohiro posted a fix for this problem, but that patch was never
applied: https://lkml.org/lkml/2013/5/26/191 .
This patch takes different approach to cure the problem. It calls
update_curr() when cputimer starts, that assure we will have updated
stats of running threads and on the next schedule tick we will account
only the runtime that elapsed from cputimer start. That also assure we
have consistent state between cpu times of individual threads and cpu
time of the process consisted by those threads.
Full reproducer (tst-cpuclock2.c):
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <stdio.h>
#include <time.h>
#include <pthread.h>
#include <stdint.h>
#include <inttypes.h>
/* Parameters for the Linux kernel ABI for CPU clocks. */
#define CPUCLOCK_SCHED 2
#define MAKE_PROCESS_CPUCLOCK(pid, clock) \
((~(clockid_t) (pid) << 3) | (clockid_t) (clock))
static pthread_barrier_t barrier;
/* Help advance the clock. */
static void *chew_cpu(void *arg)
{
pthread_barrier_wait(&barrier);
while (1) ;
return NULL;
}
/* Don't use the glibc wrapper. */
static int do_nanosleep(int flags, const struct timespec *req)
{
clockid_t clock_id = MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED);
return syscall(SYS_clock_nanosleep, clock_id, flags, req, NULL);
}
static int64_t tsdiff(const struct timespec *before, const struct timespec *after)
{
int64_t before_i = before->tv_sec * 1000000000ULL + before->tv_nsec;
int64_t after_i = after->tv_sec * 1000000000ULL + after->tv_nsec;
return after_i - before_i;
}
int main(void)
{
int result = 0;
pthread_t th;
pthread_barrier_init(&barrier, NULL, 2);
if (pthread_create(&th, NULL, chew_cpu, NULL) != 0) {
perror("pthread_create");
return 1;
}
pthread_barrier_wait(&barrier);
/* The test. */
struct timespec before, after, sleeptimeabs;
int64_t sleepdiff, diffabs;
const struct timespec sleeptime = {.tv_sec = 0,.tv_nsec = 100000000 };
/* The relative nanosleep. Not sure why this is needed, but its presence
seems to make it easier to reproduce the problem. */
if (do_nanosleep(0, &sleeptime) != 0) {
perror("clock_nanosleep");
return 1;
}
/* Get the current time. */
if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &before) < 0) {
perror("clock_gettime[2]");
return 1;
}
/* Compute the absolute sleep time based on the current time. */
uint64_t nsec = before.tv_nsec + sleeptime.tv_nsec;
sleeptimeabs.tv_sec = before.tv_sec + nsec / 1000000000;
sleeptimeabs.tv_nsec = nsec % 1000000000;
/* Sleep for the computed time. */
if (do_nanosleep(TIMER_ABSTIME, &sleeptimeabs) != 0) {
perror("absolute clock_nanosleep");
return 1;
}
/* Get the time after the sleep. */
if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &after) < 0) {
perror("clock_gettime[3]");
return 1;
}
/* The time after sleep should always be equal to or after the absolute sleep
time passed to clock_nanosleep. */
sleepdiff = tsdiff(&sleeptimeabs, &after);
if (sleepdiff < 0) {
printf("absolute clock_nanosleep woke too early: %" PRId64 "\n", sleepdiff);
result = 1;
printf("Before %llu.%09llu\n", before.tv_sec, before.tv_nsec);
printf("After %llu.%09llu\n", after.tv_sec, after.tv_nsec);
printf("Sleep %llu.%09llu\n", sleeptimeabs.tv_sec, sleeptimeabs.tv_nsec);
}
/* The difference between the timestamps taken before and after the
clock_nanosleep call should be equal to or more than the duration of the
sleep. */
diffabs = tsdiff(&before, &after);
if (diffabs < sleeptime.tv_nsec) {
printf("clock_gettime difference too small: %" PRId64 "\n", diffabs);
result = 1;
}
pthread_cancel(th);
return result;
}
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141112155843.GA24803@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When a CPU hotplugged out, we call perf_remove_from_context() (via
perf_event_exit_cpu()) to rip each CPU-bound event out of its PMU's cpu
context, but leave siblings grouped together. Freeing of these events is
left to the mercy of the usual refcounting.
When a CPU-bound event's refcount drops to zero we cross-call to
__perf_remove_from_context() to clean it up, detaching grouped siblings.
This works when the relevant CPU is online, but will fail if the CPU is
currently offline, and we won't detach the event from its siblings
before freeing the event, leaving the sibling list corrupt. If the
sibling list is later walked (e.g. because the CPU cam online again
before a remaining sibling's refcount drops to zero), we will walk the
now corrupted siblings list, potentially dereferencing garbage values.
Given that the events should never be scheduled again (as we removed
them from their context), we can simply detatch siblings when the CPU
goes down in the first place. If the CPU comes back online, the
redundant call to __perf_remove_from_context() is safe.
Reported-by: Drew Richardson <drew.richardson@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: vincent.weaver@maine.edu
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1415203904-25308-2-git-send-email-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The IA64_HP_SIM dependency on PM_RUNTIME should be done in the arch
Kconfig instead of in the PM core. Move it accordingly.
NOTE: arch/ia64/Kconfig currently does a 'select PM', which since
commit 1eb208aea3 (PM: Make CONFIG_PM depend on (CONFIG_PM_SLEEP ||
CONFIG_PM_RUNTIME)) is effectively a noop unless PM_SLEEP or
PM_RUNTIME are set elsewhere.
Signed-off-by: Kevin Hilman <khilman@linaro.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Pull ACPI and power management fixes from Rafael Wysocki:
"These are three regression fixes, two recent (generic power domains,
suspend-to-idle) and one older (cpufreq), an ACPI blacklist entry for
one more machine having problems with Windows 8 compatibility, a minor
cpufreq driver fix (cpufreq-dt) and a fixup for new callback
definitions (generic power domains).
Specifics:
- Fix a crash in the suspend-to-idle code path introduced by a recent
commit that forgot to check a pointer against NULL before
dereferencing it (Dmitry Eremin-Solenikov).
- Fix a boot crash on Exynos5 introduced by a recent commit making
that platform use generic Device Tree bindings for power domains
which exposed a weakness in the generic power domains framework
leading to that crash (Ulf Hansson).
- Fix a crash during system resume on systems where cpufreq depends
on Operation Performance Points (OPP) for functionality, but
CONFIG_OPP is not set. This leads the cpufreq driver registration
to fail, but the resume code attempts to restore the pre-suspend
cpufreq configuration (which does not exist) nevertheless and
crashes. From Geert Uytterhoeven.
- Add a new ACPI blacklist entry for Dell Vostro 3546 that has
problems if it is reported as Windows 8 compatible to the BIOS
(Adam Lee).
- Fix swapped arguments in an error message in the cpufreq-dt driver
(Abhilash Kesavan).
- Fix up the prototypes of new callbacks in struct generic_pm_domain
to make them more useful. Users of those callbacks will be added
in 3.19 and it's better for them to be based on the correct struct
definition in mainline from the start. From Ulf Hansson and Kevin
Hilman"
* tag 'pm+acpi-3.18-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
PM / Domains: Fix initial default state of the need_restore flag
PM / sleep: Fix entering suspend-to-IDLE if no freeze_oops is set
PM / Domains: Change prototype for the attach and detach callbacks
cpufreq: Avoid crash in resume on SMP without OPP
cpufreq: cpufreq-dt: Fix arguments in clock failure error message
ACPI / blacklist: blacklist Win8 OSI for Dell Vostro 3546
On the function_graph tracer, the print_graph_irq() function prints a
trace line with the flag ==========> on an irq handler entry, and the
flag <========== on an irq handler return.
But when the latency-format is enable, it is not printing the
latency-format flags, causing the following error in the trace output:
0) ==========> |
0) d... | smp_apic_timer_interrupt() {
This patch fixes this issue by printing the latency-format flags when
it is enable.
Link: http://lkml.kernel.org/r/7c2e226dac20c940b6242178fab7f0e3c9b5ce58.1415233316.git.bristot@redhat.com
Reviewed-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Conflicts:
drivers/net/ethernet/chelsio/cxgb4vf/sge.c
drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
sge.c was overlapping two changes, one to use the new
__dev_alloc_page() in net-next, and one to use s->fl_pg_order in net.
ixgbe_phy.c was a set of overlapping whitespace changes.
Signed-off-by: David S. Miller <davem@davemloft.net>
Using seq_printf to print a simple string or a single character is a
lot more expensive than it needs to be, since seq_puts and seq_putc
exist.
These patches do
seq_printf(m, s) -> seq_puts(m, s)
seq_printf(m, "%s", s) -> seq_puts(m, s)
seq_printf(m, "%c", c) -> seq_putc(m, c)
Subsequent patches will simplify further.
Link: http://lkml.kernel.org/r/1415479332-25944-2-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently kdb's ftdump command will livelock by constantly printk'ing
the empty string at KERN_EMERG level if it run when the ftrace system is
not in use. This occurs because trace_empty() never returns false when
the ring buffers are left at the start of a non-consuming read [launched
by ring_buffer_read_start()].
This patch changes the loop exit condition to use the result of
trace_find_next_entry_inc(). Effectively this switches the non-consuming
kdb dumper to follow the approach of the non-consuming userspace
interface [s_next()] rather than the consuming ftrace_dump().
Link: http://lkml.kernel.org/r/1415277716-19419-3-git-send-email-daniel.thompson@linaro.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently kdb's ftdump command unconditionally crashes due to a null
pointer de-reference whenever the command is run. This in turn causes
the kernel to panic.
The abridged stacktrace (gathered with ARCH=arm) is:
--- cut here ---
[<c09535ac>] (panic) from [<c02132dc>] (die+0x264/0x440)
[<c02132dc>] (die) from [<c0952eb8>]
(__do_kernel_fault.part.11+0x74/0x84)
[<c0952eb8>] (__do_kernel_fault.part.11) from [<c021f954>]
(do_page_fault+0x1d0/0x3c4)
[<c021f954>] (do_page_fault) from [<c020846c>] (do_DataAbort+0x48/0xac)
[<c020846c>] (do_DataAbort) from [<c0213c58>] (__dabt_svc+0x38/0x60)
Exception stack(0xc0deba88 to 0xc0debad0)
ba80: e8c29180 00000001 e9854304 e9854300 c0f567d8
c0df2580
baa0: 00000000 00000000 00000000 c0f117b8 c0e3a3c0 c0debb0c 00000000
c0debad0
bac0: 0000672e c02f4d60 60000193 ffffffff
[<c0213c58>] (__dabt_svc) from [<c02f4d60>] (kdb_ftdump+0x1e4/0x3d8)
[<c02f4d60>] (kdb_ftdump) from [<c02ce328>] (kdb_parse+0x2b8/0x698)
[<c02ce328>] (kdb_parse) from [<c02ceef0>] (kdb_main_loop+0x52c/0x784)
[<c02ceef0>] (kdb_main_loop) from [<c02d1b0c>] (kdb_stub+0x238/0x490)
--- cut here ---
The NULL deref occurs due to the initialized use of struct trace_iter's
buffer_iter member.
This is a regression, albeit a fairly elderly one. It was introduced
by commit 6d158a813e ("tracing: Remove NR_CPUS array from
trace_iterator").
This patch solves this by providing a collection of ring_buffer_iter(s)
and using this to initialize buffer_iter. Note that static allocation
is used solely because the trace_iter itself is also static allocated.
Static allocation also means that we have to NULL-ify the pointer during
cleanup to avoid use-after-free problems.
Link: http://lkml.kernel.org/r/1415277716-19419-2-git-send-email-daniel.thompson@linaro.org
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
According to the documentation, adding "traceoff_on_warning" to the boot
command line should be enough to enable the feature. But right now it is
necessary to specify "traceoff_on_warning=". Along with fixing that, also
verify if the value passed, if any, is either "0" or "off".
Link: http://lkml.kernel.org/r/20141112231400.GL12281@uudg.org
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
With the new logic, if only a single user of ftrace function hooks is
used, it will get its own trampoline assigned to it.
The problem is that the control_ops is an indirect ops that perf ops
uses. What that means is that when perf registers its ops with
register_ftrace_function(), it has the CONTROL flag set and gets added
to the control list instead of the global ftrace list. The control_ops
gets added to that instead and the mcount trampoline calls the control_ops
function. The control_ops function will iterate the control list and
call the ops functions that are attached to it.
But currently the trampoline is added to the perf ops and not the
control ops, and when ftrace tries to find a trampoline hook for it,
it fails to find one and gives the following splat:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 10133 at kernel/trace/ftrace.c:2033 ftrace_get_addr_new+0x6f/0xc0()
Modules linked in: [...]
CPU: 0 PID: 10133 Comm: perf Tainted: P 3.18.0-rc1-test+ #388
Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
00000000000007f1 ffff8800c2643bc8 ffffffff814fca6e ffff88011ea0ed01
0000000000000000 ffff8800c2643c08 ffffffff81041ffd 0000000000000000
ffffffff810c388c ffffffff81a5a350 ffff880119b00000 ffffffff810001c8
Call Trace:
[<ffffffff814fca6e>] dump_stack+0x46/0x58
[<ffffffff81041ffd>] warn_slowpath_common+0x81/0x9b
[<ffffffff810c388c>] ? ftrace_get_addr_new+0x6f/0xc0
[<ffffffff810001c8>] ? 0xffffffff810001c8
[<ffffffff81042031>] warn_slowpath_null+0x1a/0x1c
[<ffffffff810c388c>] ftrace_get_addr_new+0x6f/0xc0
[<ffffffff8102e938>] ftrace_replace_code+0xd6/0x334
[<ffffffff810c4116>] ftrace_modify_all_code+0x41/0xc5
[<ffffffff8102eba6>] arch_ftrace_update_code+0x10/0x19
[<ffffffff810c293c>] ftrace_run_update_code+0x21/0x42
[<ffffffff810c298f>] ftrace_startup_enable+0x32/0x34
[<ffffffff810c3049>] ftrace_startup+0x14e/0x15a
[<ffffffff810c307c>] register_ftrace_function+0x27/0x40
[<ffffffff810dc118>] perf_ftrace_event_register+0x3e/0xee
[<ffffffff810dbfbe>] perf_trace_init+0x29d/0x2a9
[<ffffffff810eb422>] perf_tp_event_init+0x27/0x3a
[<ffffffff810f18bc>] perf_init_event+0x9e/0xed
[<ffffffff810f1ba4>] perf_event_alloc+0x299/0x330
[<ffffffff810f236b>] SYSC_perf_event_open+0x3ee/0x816
[<ffffffff8115a066>] ? mntput+0x2d/0x2f
[<ffffffff81142b00>] ? __fput+0xa7/0x1b2
[<ffffffff81091300>] ? do_gettimeofday+0x22/0x3a
[<ffffffff810f279c>] SyS_perf_event_open+0x9/0xb
[<ffffffff81502a92>] system_call_fastpath+0x12/0x17
---[ end trace 81a53565150e4982 ]---
Bad trampoline accounting at: ffffffff810001c8 (run_init_process+0x0/0x2d) (10000001)
Update the control_ops trampoline instead of the perf ops one.
Reported-by: lkp@01.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit affines rcu_tasks_kthread() to the housekeeping CPUs
in CONFIG_NO_HZ_FULL builds. This is just a default, so systems
administrators are free to put this kthread somewhere else if they wish.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Pull audit fixes from Paul Moore:
"After he sent the initial audit pull request for 3.18, Eric asked me
to take over the management of the audit tree, hence this pull request
to fix a couple of problems with audit.
As you can see below, the changes are minimal: adding some whitespace
to a string so userspace parses it correctly, and fixing a problem
with audit's usage of fsnotify that was causing audit watch rules to
be lost. Neither of these patches were very controversial on the
mailing lists and they fix real problems, getting them into 3.18 would
be a good thing"
* 'stable-3.18' of git://git.infradead.org/users/pcmoore/audit:
audit: keep inode pinned
audit: AUDIT_FEATURE_CHANGE message format missing delimiting space
Audit rules disappear when an inode they watch is evicted from the cache.
This is likely not what we want.
The guilty commit is "fsnotify: allow marks to not pin inodes in core",
which didn't take into account that audit_tree adds watches with a zero
mask.
Adding any mask should fix this.
Fixes: 90b1e7a578 ("fsnotify: allow marks to not pin inodes in core")
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org # 2.6.36+
Signed-off-by: Paul Moore <pmoore@redhat.com>
The only code that references tracing_sched_switch_trace() and
tracing_sched_wakeup_trace() is the wakeup latency tracer. Those
two functions use to belong to the sched_switch tracer which has
long been removed. These functions were left behind because the
wakeup latency tracer used them. But since the wakeup latency tracer
is the only one to use them, they should be static functions inside
that code.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
After the previous patch it is clear that "tracer_enabled" can never be
true, we can remove the "if (tracer_enabled)" code in probe_sched_switch()
and probe_sched_wakeup(). Plus we can obviously remove tracer_enabled,
ctx_trace, and sched_stopped as well.
Link: http://lkml.kernel.org/p/20140723193503.GA30217@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
With the introduction of the dynamic trampolines, it is useful that if
things go wrong that ftrace_bug() produces more information about what
the current state is. This can help debug issues that may arise.
Ftrace has lots of checks to make sure that the state of the system it
touchs is exactly what it expects it to be. When it detects an abnormality
it calls ftrace_bug() and disables itself to prevent any further damage.
It is crucial that ftrace_bug() produces sufficient information that
can be used to debug the situation.
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Borislav Petkov <bp@suse.de>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When the static ftrace_ops (like function tracer) enables tracing, and it
is the only callback that is referencing a function, a trampoline is
dynamically allocated to the function that calls the callback directly
instead of calling a loop function that iterates over all the registered
ftrace ops (if more than one ops is registered).
But when it comes to dynamically allocated ftrace_ops, where they may be
freed, on a CONFIG_PREEMPT kernel there's no way to know when it is safe
to free the trampoline. If a task was preempted while executing on the
trampoline, there's currently no way to know when it will be off that
trampoline.
But this is not true when it comes to !CONFIG_PREEMPT. The current method
of calling schedule_on_each_cpu() will force tasks off the trampoline,
becaues they can not schedule while on it (kernel preemption is not
configured). That means it is safe to free a dynamically allocated
ftrace ops trampoline when CONFIG_PREEMPT is not configured.
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Borislav Petkov <bp@suse.de>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently if an active CPU fails to respond to a roundup request the CPU
that requested the roundup will become stuck. This needlessly reduces the
robustness of the debugger.
This patch introduces a timeout allowing the system state to be examined
even when the system contains unresponsive processors. It also modifies
kdb's cpu command to make it censor attempts to switch to unresponsive
processors and to report their state as (D)ead.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently kiosk mode must be explicitly requested by the bootloader or
userspace. It is convenient to be able to change the default value in a
similar manner to CONFIG_MAGIC_SYSRQ_DEFAULT_MASK.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently all kdb commands are enabled whenever kdb is deployed. This
makes it difficult to deploy kdb to help debug certain types of
systems.
Android phones provide one example; the FIQ debugger found on some
Android devices has a deliberately weak set of commands to allow the
debugger to enabled very late in the production cycle.
Certain kiosk environments offer another interesting case where an
engineer might wish to probe the system state using passive inspection
commands without providing sufficient power for a passer by to root it.
Without any restrictions, obtaining the root rights via KDB is a matter of
a few commands, and works everywhere. For example, log in as a normal
user:
cbou:~$ id
uid=1001(cbou) gid=1001(cbou) groups=1001(cbou)
Now enter KDB (for example via sysrq):
Entering kdb (current=0xffff8800065bc740, pid 920) due to Keyboard Entry
kdb> ps
23 sleeping system daemon (state M) processes suppressed,
use 'ps A' to see all.
Task Addr Pid Parent [*] cpu State Thread Command
0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash
0xffff880007078000 1 0 0 0 S 0xffff8800070782e0 init
[...snip...]
0xffff8800065be3c0 918 1 0 0 S 0xffff8800065be6a0 getty
0xffff8800065b9c80 919 1 0 0 S 0xffff8800065b9f60 login
0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash
All we need is the offset of cred pointers. We can look up the offset in
the distro's kernel source, but it is unnecessary. We can just start
dumping init's task_struct, until we see the process name:
kdb> md 0xffff880007078000
0xffff880007078000 0000000000000001 ffff88000703c000 ................
0xffff880007078010 0040210000000002 0000000000000000 .....!@.........
[...snip...]
0xffff8800070782b0 ffff8800073e0580 ffff8800073e0580 ..>.......>.....
0xffff8800070782c0 0000000074696e69 0000000000000000 init............
^ Here, 'init'. Creds are just above it, so the offset is 0x02b0.
Now we set up init's creds for our non-privileged shell:
kdb> mm 0xffff8800065bc740+0x02b0 0xffff8800073e0580
0xffff8800065bc9f0 = 0xffff8800073e0580
kdb> mm 0xffff8800065bc740+0x02b8 0xffff8800073e0580
0xffff8800065bc9f8 = 0xffff8800073e0580
And thus gaining the root:
kdb> go
cbou:~$ id
uid=0(root) gid=0(root) groups=0(root)
cbou:~$ bash
root:~#
p.s. No distro enables kdb by default (although, with a nice KDB-over-KMS
feature availability, I would expect at least some would enable it), so
it's not actually some kind of a major issue.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This patch introduces several new flags to collect kdb commands into
groups (later allowing them to be optionally disabled).
This follows similar prior art to enable/disable magic sysrq
commands.
The commands have been categorized as follows:
Always on: go (w/o args), env, set, help, ?, cpu (w/o args), sr,
dmesg, disable_nmi, defcmd, summary, grephelp
Mem read: md, mdr, mdp, mds, ef, bt (with args), per_cpu
Mem write: mm
Reg read: rd
Reg write: go (with args), rm
Inspect: bt (w/o args), btp, bta, btc, btt, ps, pid, lsmod
Flow ctrl: bp, bl, bph, bc, be, bd, ss
Signal: kill
Reboot: reboot
All: cpu, kgdb, (and all of the above), nmi_console
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The actual values of KDB_REPEAT_* enum values and overall logic stayed
the same, but we now treat the values as flags.
This makes it possible to add other flags and combine them, plus makes
the code a lot simpler and shorter. But functionality-wise, there should
be no changes.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
commit 63662139e5 attempted to patch a
leak (which would only happen on OOM, ie. never), but it didn't quite
work.
This rewrites the code to be as simple as possible. add_sysfs_param()
adds a parameter. If it fails, it's the caller's responsibility to
clean up the parameters which already exist.
The kzalloc-then-always-krealloc pattern is perhaps overly simplistic,
but this code has clearly confused people. It worked on me...
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Remove stop_machine from module unloading by adding new reference
counting algorithm.
This atomic refcounter works like a semaphore, it can get (be
incremented) only when the counter is not 0. When loading a module,
kmodule subsystem sets the counter MODULE_REF_BASE (= 1). And when
unloading the module, it subtracts MODULE_REF_BASE from the counter.
If no one refers the module, the refcounter becomes 0 and we can
remove the module safely. If someone referes it, we try to recover
the counter by adding MODULE_REF_BASE unless the counter becomes 0,
because the referrer can put the module right before recovering.
If the recovering is failed, we can get the 0 refcount and it
never be incremented again, it can be removed safely too.
Note that __module_get() forcibly gets the module refcounter,
users should use try_module_get() instead of that.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Replace module_ref per-cpu complex reference counter with
an atomic_t simple refcnt. This is for code simplification.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Actually since module_bug_list should be used in BUG context,
we may not need this. But for someone who want to use this
from normal context, this makes module_bug_list an RCU list.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Unlink module from module list with RCU synchronizing instead
of using stop_machine(). Since module list is already protected
by rcu, we don't need stop_machine() anymore.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Wait for RCU synchronizing on failure path of module loading
before releasing struct module, because the memory of mod->list
can still be accessed by list walkers (e.g. kallsyms).
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
If the read loop in trace_buffers_splice_read() keeps failing due to
memory allocation failures without reading even a single page then this
function will keep busy looping.
Remove the risk for that by exiting the function if memory allocation
failures are seen.
Link: http://lkml.kernel.org/r/1415309167-2373-2-git-send-email-rabin@rab.in
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
On a !PREEMPT kernel, attempting to use trace-cmd results in a soft
lockup:
# trace-cmd record -e raw_syscalls:* -F false
NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [trace-cmd:61]
...
Call Trace:
[<ffffffff8105b580>] ? __wake_up_common+0x90/0x90
[<ffffffff81092e25>] wait_on_pipe+0x35/0x40
[<ffffffff810936e3>] tracing_buffers_splice_read+0x2e3/0x3c0
[<ffffffff81093300>] ? tracing_stats_read+0x2a0/0x2a0
[<ffffffff812d10ab>] ? _raw_spin_unlock+0x2b/0x40
[<ffffffff810dc87b>] ? do_read_fault+0x21b/0x290
[<ffffffff810de56a>] ? handle_mm_fault+0x2ba/0xbd0
[<ffffffff81095c80>] ? trace_event_buffer_lock_reserve+0x40/0x80
[<ffffffff810951e2>] ? trace_buffer_lock_reserve+0x22/0x60
[<ffffffff81095c80>] ? trace_event_buffer_lock_reserve+0x40/0x80
[<ffffffff8112415d>] do_splice_to+0x6d/0x90
[<ffffffff81126971>] SyS_splice+0x7c1/0x800
[<ffffffff812d1edd>] tracesys_phase2+0xd3/0xd8
The problem is this: tracing_buffers_splice_read() calls
ring_buffer_wait() to wait for data in the ring buffers. The buffers
are not empty so ring_buffer_wait() returns immediately. But
tracing_buffers_splice_read() calls ring_buffer_read_page() with full=1,
meaning it only wants to read a full page. When the full page is not
available, tracing_buffers_splice_read() tries to wait again with
ring_buffer_wait(), which again returns immediately, and so on.
Fix this by adding a "full" argument to ring_buffer_wait() which will
make ring_buffer_wait() wait until the writer has left the reader's
page, i.e. until full-page reads will succeed.
Link: http://lkml.kernel.org/r/1415645194-25379-1-git-send-email-rabin@rab.in
Cc: stable@vger.kernel.org # 3.16+
Fixes: b1169cc69b ("tracing: Remove mock up poll wait function")
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
On latest mm + KASan patchset I've got this:
==================================================================
BUG: AddressSanitizer: out of bounds access in sched_init_smp+0x3ba/0x62c at addr ffff88006d4bee6c
=============================================================================
BUG kmalloc-8 (Not tainted): kasan error
-----------------------------------------------------------------------------
Disabling lock debugging due to kernel taint
INFO: Allocated in alloc_vfsmnt+0xb0/0x2c0 age=75 cpu=0 pid=0
__slab_alloc+0x4b4/0x4f0
__kmalloc_track_caller+0x15f/0x1e0
kstrdup+0x44/0x90
alloc_vfsmnt+0xb0/0x2c0
vfs_kern_mount+0x35/0x190
kern_mount_data+0x25/0x50
pid_ns_prepare_proc+0x19/0x50
alloc_pid+0x5e2/0x630
copy_process.part.41+0xdf5/0x2aa0
do_fork+0xf5/0x460
kernel_thread+0x21/0x30
rest_init+0x1e/0x90
start_kernel+0x522/0x531
x86_64_start_reservations+0x2a/0x2c
x86_64_start_kernel+0x15b/0x16a
INFO: Slab 0xffffea0001b52f80 objects=24 used=22 fp=0xffff88006d4befc0 flags=0x100000000004080
INFO: Object 0xffff88006d4bed20 @offset=3360 fp=0xffff88006d4bee70
Bytes b4 ffff88006d4bed10: 00 00 00 00 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ
Object ffff88006d4bed20: 70 72 6f 63 00 6b 6b a5 proc.kk.
Redzone ffff88006d4bed28: cc cc cc cc cc cc cc cc ........
Padding ffff88006d4bee68: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
CPU: 0 PID: 1 Comm: swapper/0 Tainted: G B 3.18.0-rc3-mm1+ #108
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
ffff88006d4be000 0000000000000000 ffff88006d4bed20 ffff88006c86fd18
ffffffff81cd0a59 0000000000000058 ffff88006d404240 ffff88006c86fd48
ffffffff811fa3a8 ffff88006d404240 ffffea0001b52f80 ffff88006d4bed20
Call Trace:
dump_stack (lib/dump_stack.c:52)
print_trailer (mm/slub.c:645)
object_err (mm/slub.c:652)
? sched_init_smp (kernel/sched/core.c:6552 kernel/sched/core.c:7063)
kasan_report_error (mm/kasan/report.c:102 mm/kasan/report.c:178)
? kasan_poison_shadow (mm/kasan/kasan.c:48)
? kasan_unpoison_shadow (mm/kasan/kasan.c:54)
? kasan_poison_shadow (mm/kasan/kasan.c:48)
? kasan_kmalloc (mm/kasan/kasan.c:311)
__asan_load4 (mm/kasan/kasan.c:371)
? sched_init_smp (kernel/sched/core.c:6552 kernel/sched/core.c:7063)
sched_init_smp (kernel/sched/core.c:6552 kernel/sched/core.c:7063)
kernel_init_freeable (init/main.c:869 init/main.c:997)
? finish_task_switch (kernel/sched/sched.h:1036 kernel/sched/core.c:2248)
? rest_init (init/main.c:924)
kernel_init (init/main.c:929)
? rest_init (init/main.c:924)
ret_from_fork (arch/x86/kernel/entry_64.S:348)
? rest_init (init/main.c:924)
Read of size 4 by task swapper/0:
Memory state around the buggy address:
ffff88006d4beb80: fc fc fc fc fc fc fc fc fc fc 00 fc fc fc fc fc
ffff88006d4bec00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88006d4bec80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88006d4bed00: fc fc fc fc 00 fc fc fc fc fc fc fc fc fc fc fc
ffff88006d4bed80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88006d4bee00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc 04 fc
^
ffff88006d4bee80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88006d4bef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88006d4bef80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff88006d4bf000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88006d4bf080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Zero 'level' (e.g. on non-NUMA system) causing out of bounds
access in this line:
sched_max_numa_distance = sched_domains_numa_distance[level - 1];
Fix this by exiting from sched_init_numa() earlier.
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Fixes: 9942f79ba ("sched/numa: Export info needed for NUMA balancing on complex topologies")
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1415372020-1871-1-git-send-email-a.ryabinin@samsung.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
