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5fbfb18d7a
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Nick Piggin 5fbfb18d7a Fix up possibly racy module refcounting 
Module refcounting is implemented with a per-cpu counter for speed.
However there is a race when tallying the counter where a reference may
be taken by one CPU and released by another.  Reference count summation
may then see the decrement without having seen the previous increment,
leading to lower than expected count.  A module which never has its
actual reference drop below 1 may return a reference count of 0 due to
this race.

Module removal generally runs under stop_machine, which prevents this
race causing bugs due to removal of in-use modules.  However there are
other real bugs in module.c code and driver code (module_refcount is
exported) where the callers do not run under stop_machine.

Fix this by maintaining running per-cpu counters for the number of
module refcount increments and the number of refcount decrements.  The
increments are tallied after the decrements, so any decrement seen will
always have its corresponding increment counted.  The final refcount is
the difference of the total increments and decrements, preventing a
low-refcount from being returned.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-05 19:50:02 -07:00
..
gcov microblaze: Enable GCOV_PROFILE_ALL 2009-09-21 14:29:21 +02:00
irq include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
power Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
time include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
trace Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
.gitignore
acct.c copy_signal() cleanup: kill taskstats_tgid_init() and acct_init_pacct() 2010-03-12 15:52:39 -08:00
async.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
audit_tree.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
audit_watch.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
audit.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
audit.h
auditfilter.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
auditsc.c audit: preface audit printk with audit 2010-04-05 13:19:45 -07:00
backtracetest.c
bounds.c kbuild: move bounds.h to include/generated 2009-12-12 13:08:14 +01:00
capability.c capabilities: Use RCU to protect task lookup in sys_capget 2009-12-10 09:42:48 +11:00
cgroup_freezer.c Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
cgroup.c cgroups: remove duplicate include 2010-03-24 16:31:19 -07:00
compat.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
configs.c
cpu.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
cpuset.c cpuset: alloc nodemask_t on the heap rather than the stack 2010-03-24 16:31:21 -07:00
cred-internals.h
cred.c Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
delayacct.c headers: taskstats_kern.h trim 2009-09-18 09:48:52 -07:00
dma.c
early_res.c x86: Do not free zero sized per cpu areas 2010-03-29 18:55:40 +02:00
elfcore.c elf coredump: add extended numbering support 2010-03-06 11:26:46 -08:00
exec_domain.c
exit.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-13 14:43:01 -08:00
extable.c
fork.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-13 14:43:01 -08:00
freezer.c sched: fix nr_uninterruptible accounting of frozen tasks really 2009-07-18 14:19:53 +02:00
futex_compat.c futex: Protect pid lookup in compat code with RCU 2009-12-09 14:22:14 +01:00
futex.c futex: Handle futex value corruption gracefully 2010-02-03 15:13:22 +01:00
groups.c
hrtimer.c hrtimers: Convert to raw_spinlocks 2009-12-14 23:55:34 +01:00
hung_task.c softlockup: Fix hung_task_check_count sysctl 2009-11-27 06:21:57 +01:00
hw_breakpoint.c Merge branch 'perf/core' into perf/urgent 2010-03-04 11:47:52 +01:00
itimer.c itimers: Fix racy writes to cpu_itimer fields 2009-11-18 16:32:12 +01:00
kallsyms.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks mutex: Better control mutex adaptive spinning config 2009-12-03 11:50:11 +01:00
Kconfig.preempt
kexec.c percpu: add __percpu sparse annotations to core kernel subsystems 2010-02-17 11:17:38 +09:00
kfifo.c kfifo: Don't use integer as NULL pointer 2010-02-16 15:11:08 -08:00
kgdb.c kgdb: Turn off tracing while in the debugger 2010-04-02 14:58:19 -05:00
kmod.c kmod: fix resource leak in call_usermodehelper_pipe() 2010-01-11 09:34:04 -08:00
kprobes.c kprobes: Calculate the index correctly when freeing the out-of-line execution slot 2010-03-11 14:06:16 +01:00
ksysfs.c Merge branch 'for-next' into for-linus 2010-03-08 16:55:37 +01:00
kthread.c cpuset: fix the problem that cpuset_mem_spread_node() returns an offline node 2010-03-24 16:31:21 -07:00
latencytop.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
lockdep_internals.h lockdep: BFS cleanup 2009-07-24 10:53:29 +02:00
lockdep_proc.c seq_file: constify seq_operations 2009-09-23 07:39:29 -07:00
lockdep_states.h
lockdep.c Merge branch 'slabh' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc 2010-04-05 09:39:11 -07:00
Makefile elf coredump: replace ELF_CORE_EXTRA_* macros by functions 2010-03-06 11:26:45 -08:00
module.c Fix up possibly racy module refcounting 2010-04-05 19:50:02 -07:00
mutex-debug.c headers: remove sched.h from interrupt.h 2009-10-11 11:20:58 -07:00
mutex-debug.h locking: Implement new raw_spinlock 2009-12-14 23:55:32 +01:00
mutex.c mutex: Better control mutex adaptive spinning config 2009-12-03 11:50:11 +01:00
mutex.h
notifier.c sched: Use lockdep-based checking on rcu_dereference() 2010-02-25 10:34:26 +01:00
ns_cgroup.c cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time 2009-09-24 07:20:58 -07:00
nsproxy.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
padata.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
panic.c panic: fix panic_timeout accuracy when running on a hypervisor 2010-03-06 11:26:33 -08:00
params.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-03-12 16:04:50 -08:00
perf_event.c Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
pid_namespace.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
pid.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-13 14:43:01 -08:00
pm_qos_params.c pm_qos: clean up racy global "name" variable 2009-10-14 15:31:10 +02:00
posix-cpu-timers.c Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-26 15:10:38 -07:00
posix-timers.c posix-timers.c: Don't export local functions 2010-02-05 14:54:10 +01:00
printk.c printk: avoid warning when CONFIG_PRINTK is disabled 2010-03-06 11:26:33 -08:00
profile.c kernel/profile.c: Switch /proc/irq/prof_cpu_mask to seq_file 2009-09-20 20:15:40 +02:00
ptrace.c ptrace: Fix ptrace_regset() comments and diagnose errors specifically 2010-02-23 13:45:26 -08:00
range.c x86: Change range end to start+size 2010-02-10 17:47:17 -08:00
rcupdate.c rcu: Make rcu_read_lock_bh_held() allow for disabled BH 2010-03-16 09:57:49 +01:00
rcutiny.c rcu: Eliminate unneeded function wrapping 2009-11-22 18:58:16 +01:00
rcutorture.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2010-03-03 07:34:18 -08:00
rcutree_plugin.h rcu: Fix holdoff for accelerated GPs for last non-dynticked CPU 2010-02-28 09:17:42 +01:00
rcutree_trace.c rcu: Stop overflowing signed integers 2010-02-25 10:34:57 +01:00
rcutree.c rcu: Fix accelerated grace periods for last non-dynticked CPU 2010-02-27 09:53:52 +01:00
rcutree.h rcu: Increase RCU CPU stall timeouts if PROVE_RCU 2010-03-11 13:38:01 +01:00
relay.c splice: comparing unsigned int < 0 2010-03-06 11:26:32 -08:00
res_counter.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
resource.c resources: add interfaces that return conflict information 2010-03-23 13:33:50 -07:00
rtmutex_common.h
rtmutex-debug.c sched: Convert pi_lock to raw_spinlock 2009-12-14 23:55:33 +01:00
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c rtmutes: Convert rtmutex.lock to raw_spinlock 2009-12-14 23:55:33 +01:00
rtmutex.h
rwsem.c
sched_clock.c sched: Fix cpu_clock() in NMIs, on !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK 2009-12-15 09:04:36 +01:00
sched_cpupri.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
sched_cpupri.h sched: Convert cpupri lock to raw_spinlock 2009-12-14 23:55:33 +01:00
sched_debug.c sched: Fix proc_sched_set_task() 2010-04-02 20:06:40 +02:00
sched_fair.c sched, rcu: Fix rcu_dereference() for RCU-lockdep 2010-03-01 09:29:58 +01:00
sched_features.h sched: Discard some old bits 2009-12-09 10:03:07 +01:00
sched_idletask.c sched: Remove the sched_class load_balance methods 2010-01-21 13:40:09 +01:00
sched_rt.c Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-03-13 14:46:18 -08:00
sched_stats.h
sched.c Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
seccomp.c
semaphore.c
signal.c kernel core: use helpers for rlimits 2010-03-06 11:26:33 -08:00
slow-work-debugfs.c SLOW_WORK: Move slow_work's proc file to debugfs 2009-12-01 08:20:31 -08:00
slow-work.c slow-work: use get_ref wrapper instead of directly calling get_ref 2010-03-29 09:13:30 -07:00
slow-work.h SLOW_WORK: CONFIG_SLOW_WORK_PROC should be CONFIG_SLOW_WORK_DEBUG 2010-03-29 09:14:47 -07:00
smp.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
softirq.c hrtimer, softirq: Fix hrtimer->softirq trampoline 2010-02-03 18:17:40 +01:00
softlockup.c softlockup: Stop spurious softlockup messages due to overflow 2010-03-21 19:30:13 +01:00
spinlock.c locking: Cleanup the name space completely 2009-12-14 23:55:33 +01:00
srcu.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
stacktrace.c
stop_machine.c percpu: add __percpu sparse annotations to core kernel subsystems 2010-02-17 11:17:38 +09:00
sys_ni.c Add generic sys_ipc wrapper 2010-03-12 15:52:32 -08:00
sys.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
sysctl_binary.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
sysctl_check.c ipv4 05/05: add sysctl to accept packets with local source addresses 2009-12-03 12:14:38 -08:00
sysctl.c sysctl extern cleanup: lockdep 2010-03-12 15:53:10 -08:00
taskstats.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
test_kprobes.c
time.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
timeconst.pl
timer.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
tracepoint.c trivial: fix typo "to to" in multiple files 2009-09-21 15:14:55 +02:00
tsacct.c mm: clean up mm_counter 2010-03-06 11:26:23 -08:00
uid16.c headers: utsname.h redux 2009-09-23 18:13:10 -07:00
up.c
user_namespace.c
user-return-notifier.c core: Clean up user return notifers use of per_cpu 2009-12-02 10:22:59 +01:00
user.c sched: Remove USER_SCHED 2010-01-21 13:40:18 +01:00
utsname_sysctl.c sysctl kernel: Remove binary sysctl logic 2009-11-12 02:04:55 -08:00
utsname.c
wait.c locking, sched: Give waitqueue spinlocks their own lockdep classes 2009-08-10 14:43:09 +02:00
workqueue.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2009-12-10 09:35:44 -08:00