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android_kernel_motorola_sm6375/kernel
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Repository files (latest commit first)
Filename Latest commit message Latest commit date
Mel Gorman 48fb6f4db9 futex: Remove unnecessary warning from get_futex_key 
Commit 65d8fc777f ("futex: Remove requirement for lock_page() in
get_futex_key()") removed an unnecessary lock_page() with the
side-effect that page->mapping needed to be treated very carefully.

Two defensive warnings were added in case any assumption was missed and
the first warning assumed a correct application would not alter a
mapping backing a futex key.  Since merging, it has not triggered for
any unexpected case but Mark Rutland reported the following bug
triggering due to the first warning.

  kernel BUG at kernel/futex.c:679!
  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
  Modules linked in:
  CPU: 0 PID: 3695 Comm: syz-executor1 Not tainted 4.13.0-rc3-00020-g307fec773ba3 #3
  Hardware name: linux,dummy-virt (DT)
  task: ffff80001e271780 task.stack: ffff000010908000
  PC is at get_futex_key+0x6a4/0xcf0 kernel/futex.c:679
  LR is at get_futex_key+0x6a4/0xcf0 kernel/futex.c:679
  pc : [<ffff00000821ac14>] lr : [<ffff00000821ac14>] pstate: 80000145

The fact that it's a bug instead of a warning was due to an unrelated
arm64 problem, but the warning itself triggered because the underlying
mapping changed.

This is an application issue but from a kernel perspective it's a
recoverable situation and the warning is unnecessary so this patch
removes the warning.  The warning may potentially be triggered with the
following test program from Mark although it may be necessary to adjust
NR_FUTEX_THREADS to be a value smaller than the number of CPUs in the
system.

    #include <linux/futex.h>
    #include <pthread.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <sys/mman.h>
    #include <sys/syscall.h>
    #include <sys/time.h>
    #include <unistd.h>

    #define NR_FUTEX_THREADS 16
    pthread_t threads[NR_FUTEX_THREADS];

    void *mem;

    #define MEM_PROT  (PROT_READ | PROT_WRITE)
    #define MEM_SIZE  65536

    static int futex_wrapper(int *uaddr, int op, int val,
                             const struct timespec *timeout,
                             int *uaddr2, int val3)
    {
        syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
    }

    void *poll_futex(void *unused)
    {
        for (;;) {
            futex_wrapper(mem, FUTEX_CMP_REQUEUE_PI, 1, NULL, mem + 4, 1);
        }
    }

    int main(int argc, char *argv[])
    {
        int i;

        mem = mmap(NULL, MEM_SIZE, MEM_PROT,
               MAP_SHARED | MAP_ANONYMOUS, -1, 0);

        printf("Mapping @ %p\n", mem);

        printf("Creating futex threads...\n");

        for (i = 0; i < NR_FUTEX_THREADS; i++)
            pthread_create(&threads[i], NULL, poll_futex, NULL);

        printf("Flipping mapping...\n");
        for (;;) {
            mmap(mem, MEM_SIZE, MEM_PROT,
                 MAP_FIXED | MAP_SHARED | MAP_ANONYMOUS, -1, 0);
        }

        return 0;
    }

Reported-and-tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org # 4.7+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-08-09 14:00:54 -07:00
..
bpf bpf: fix bpf_prog_get_info_by_fd to dump correct xlated_prog_len 2017-07-29 23:29:41 -07:00
cgroup cpuset: fix a deadlock due to incomplete patching of cpusets_enabled() 2017-08-02 17:16:12 -07:00
configs config: android-base: disable CONFIG_NFSD and CONFIG_NFS_FS 2017-06-09 11:47:38 +02:00
debug sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:12:48 -07:00
gcov gcov: support GCC 7.1 2017-05-12 15:57:15 -07:00
irq genirq/cpuhotplug: Revert "Set force affinity flag on hotplug migration" 2017-07-27 15:40:02 +02:00
livepatch livepatch: Fix stacking of patches with respect to RCU 2017-06-20 10:42:19 +02:00
locking Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:11:23 -07:00
power More power management updates for v4.13-rc1 2017-07-10 15:16:21 -07:00
printk Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2017-07-05 11:11:26 -07:00
rcu rcu: Remove RCU CPU stall warnings from Tiny RCU 2017-06-08 18:52:45 -07:00
sched sched/core: Fix some documentation build warnings 2017-07-25 11:17:02 +02:00
time timers: Fix overflow in get_next_timer_interrupt 2017-08-01 14:20:53 +02:00
trace trace: fix the errors caused by incompatible type of RCU variables 2017-07-20 09:27:29 -04:00
.gitignore
acct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
async.c async: Adjust system_state checks 2017-05-23 10:01:37 +02:00
audit.c Merge branch 'stable-4.13' of git://git.infradead.org/users/pcmoore/audit 2017-07-20 10:22:26 -07:00
audit.h audit: style fix 2017-06-12 18:07:43 -04:00
audit_fsnotify.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit_tree.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit_watch.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
auditfilter.c audit: kernel generated netlink traffic should have a portid of 0 2017-05-02 10:16:05 -04:00
auditsc.c Merge branch 'stable-4.13' of git://git.infradead.org/users/pcmoore/audit 2017-07-05 11:24:05 -07:00
backtracetest.c
bounds.c
capability.c
compat.c Merge branch 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-06 20:57:13 -07:00
configs.c
context_tracking.c
cpu.c smp/hotplug: Replace BUG_ON and react useful 2017-07-11 22:25:44 +02:00
cpu_pm.c
crash_core.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
crash_dump.c
cred.c doc: ReSTify credentials.txt 2017-05-18 10:30:19 -06:00
delayacct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c kernel/exit.c: avoid undefined behaviour when calling wait4() 2017-07-10 16:32:36 -07:00
extable.c lib/extable.c: use bsearch() library function in search_extable() 2017-07-10 16:32:35 -07:00
fork.c fork,random: use get_random_canary() to set tsk->stack_canary 2017-07-12 16:26:03 -07:00
freezer.c
futex.c futex: Remove unnecessary warning from get_futex_key 2017-08-09 14:00:54 -07:00
futex_compat.c
groups.c kernel/groups.c: use sort library function 2017-07-10 16:32:34 -07:00
hung_task.c kernel/hung_task.c: defer showing held locks 2017-05-08 17:15:10 -07:00
irq_work.c
jump_label.c jump_label: Reorder hotplug lock and jump_label_lock 2017-05-26 10:10:45 +02:00
kallsyms.c kernel/kallsyms.c: replace all_var with IS_ENABLED(CONFIG_KALLSYMS_ALL) 2017-07-10 16:32:34 -07:00
kcmp.c kcmp: add KCMP_EPOLL_TFD mode to compare epoll target files 2017-07-12 16:26:01 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: simplify interrupt check 2017-05-08 17:15:12 -07:00
kexec.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
kexec_core.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
kexec_file.c kexec_file: adjust declaration of kexec_purgatory 2017-07-12 16:26:02 -07:00
kexec_internal.h kexec_file: adjust declaration of kexec_purgatory 2017-07-12 16:26:02 -07:00
kmod.c kmod: throttle kmod thread limit 2017-07-14 15:05:13 -07:00
kprobes.c kprobes: Ensure that jprobe probepoints are at function entry 2017-07-08 11:05:35 +02:00
ksysfs.c kexec: move vmcoreinfo out of the kernel's .bss section 2017-07-12 16:25:59 -07:00
kthread.c cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups 2017-03-17 10:18:47 -04:00
latencytop.c sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h> 2017-03-02 08:42:39 +01:00
Makefile kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
membarrier.c Fix: Disable sys_membarrier when nohz_full is enabled 2017-01-23 11:32:16 -08:00
memremap.c mm, memory_hotplug: replace for_device by want_memblock in arch_add_memory 2017-07-06 16:24:32 -07:00
module-internal.h
module.c Modules updates for v4.13 2017-07-12 17:22:01 -07:00
module_signing.c
notifier.c kernel/notifier.c: simplify expression 2017-02-24 17:46:56 -08:00
nsproxy.c perf: Add PERF_RECORD_NAMESPACES to include namespaces related info 2017-03-13 15:57:41 -03:00
padata.c padata: Avoid nested calls to cpus_read_lock() in pcrypt_init_padata() 2017-05-26 10:10:37 +02:00
panic.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
params.c boot/param: Move next_arg() function to lib/cmdline.c for later reuse 2017-04-18 10:37:13 +02:00
pid.c pid: kill pidhash_size in pidhash_init() 2017-08-02 16:34:46 -07:00
pid_namespace.c pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes 2017-05-13 17:26:01 -05:00
profile.c sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h> 2017-03-02 08:42:39 +01:00
ptrace.c ptrace: Properly initialize ptracer_cred on fork 2017-05-23 07:40:44 -05:00
range.c
reboot.c
relay.c Merge branch 'work.splice' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-05-02 11:38:06 -07:00
resource.c
seccomp.c seccomp: Switch from atomic_t to recount_t 2017-06-26 09:24:00 -07:00
signal.c Fix compat_sys_sigpending breakage 2017-08-06 11:48:27 -07:00
smp.c smp, cpumask: Use non-atomic cpumask_{set,clear}_cpu() 2017-05-23 10:01:32 +02:00
smpboot.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
smpboot.h
softirq.c sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore_flags() 2017-04-11 09:06:32 +02:00
stacktrace.c stacktrace/x86: add function for detecting reliable stack traces 2017-03-08 09:18:02 +01:00
stop_machine.c stop_machine: Provide stop_machine_cpuslocked() 2017-05-26 10:10:36 +02:00
sys.c fix a braino in compat_sys_getrlimit() 2017-07-12 09:15:00 -07:00
sys_ni.c
sysctl.c kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
sysctl_binary.c kernel/sysctl_binary.c: check name array length in deprecated_sysctl_warning() 2017-07-12 16:26:00 -07:00
task_work.c
taskstats.c taskstats: add e/u/stime for TGID command 2017-05-08 17:15:12 -07:00
test_kprobes.c
torture.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/clock.h> 2017-03-02 08:42:27 +01:00
tracepoint.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
tsacct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
ucount.c ucount: Remove the atomicity from ucount->count 2017-03-06 15:26:37 -06:00
uid16.c sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h> 2017-03-02 08:42:31 +01:00
up.c
user-return-notifier.c
user.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/user.h> 2017-03-02 08:42:29 +01:00
user_namespace.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h> 2017-03-02 08:42:29 +01:00
utsname.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
utsname_sysctl.c sched/headers: Remove <linux/rwsem.h> from <linux/sched.h> 2017-03-03 01:45:36 +01:00
watchdog.c kernel/watchdog.c: use better pr_fmt prefix 2017-07-14 15:05:13 -07:00
watchdog_hld.c kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
workqueue.c workqueue: Work around edge cases for calc of pool's cpumask 2017-07-28 11:05:52 -04:00
workqueue_internal.h