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649e9c70da
linux/kernel
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Oleg Nesterov 649e9c70da tracing: Introduce trace_create_cpu_file() and tracing_get_cpu() 
Every "file_operations" used by tracing_init_debugfs_percpu is buggy.
f_op->open/etc does:

	1. struct trace_cpu *tc = inode->i_private;
	   struct trace_array *tr = tc->tr;

	2. trace_array_get(tr) or fail;

	3. do_something(tc);

But tc (and tr) can be already freed before trace_array_get() is called.
And it doesn't matter whether this file is per-cpu or it was created by
init_tracer_debugfs(), free_percpu() or kfree() are equally bad.

Note that even 1. is not safe, the freed memory can be unmapped. But even
if it was safe trace_array_get() can wrongly succeed if we also race with
the next new_instance_create() which can re-allocate the same tr, or tc
was overwritten and ->tr points to the valid tr. In this case 3. uses the
freed/reused memory.

Add the new trivial helper, trace_create_cpu_file() which simply calls
trace_create_file() and encodes "cpu" in "struct inode". Another helper,
tracing_get_cpu() will be used to read cpu_nr-or-RING_BUFFER_ALL_CPUS.

The patch abuses ->i_cdev to encode the number, it is never used unless
the file is S_ISCHR(). But we could use something else, say, i_bytes or
even ->d_fsdata. In any case this hack is hidden inside these 2 helpers,
it would be trivial to change them if needed.

This patch only changes tracing_init_debugfs_percpu() to use the new
trace_create_cpu_file(), the next patches will change file_operations.

Note: tracing_get_cpu(inode) is always safe but you can't trust the
result unless trace_array_get() was called, without trace_types_lock
which acts as a barrier it can wrongly return RING_BUFFER_ALL_CPUS.

Link: http://lkml.kernel.org/r/20130723152554.GA23710@redhat.com

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2013-07-24 11:22:13 -04:00
..
cpu idle: Enable interrupts in the weak arch_cpu_idle() implementation 2013-06-14 23:01:05 +02:00
debug kgdb/sysrq: fix inconstistent help message of sysrq key 2013-04-30 17:04:10 -07:00
events perf: Fix perf_lock_task_context() vs RCU 2013-07-12 11:11:09 +02:00
gcov kernel/gcov: remove depends on CONFIG_EXPERIMENTAL 2013-01-11 11:39:33 -08:00
irq Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-07-13 15:37:30 -07:00
power Merge branch 'akpm' (updates from Andrew Morton) 2013-07-03 17:12:13 -07:00
sched sched: Fix HRTICK 2013-07-12 13:52:58 +02:00
time tick: broadcast: Check broadcast mode on CPU hotplug 2013-07-12 12:35:40 +02:00
trace tracing: Introduce trace_create_cpu_file() and tracing_get_cpu() 2013-07-24 11:22:13 -04:00
.gitignore kernel/hz.bc: ignore. 2013-04-22 07:09:06 -07:00
acct.c fs: Fix hang with BSD accounting on frozen filesystem 2013-05-04 14:57:58 -04:00
async.c async: rename and redefine async_func_ptr 2013-03-12 13:59:14 -07:00
audit_tree.c kernel/audit_tree.c:audit_add_tree_rule(): protect `rule' from kill_rules() 2013-06-12 16:29:46 -07:00
audit_watch.c audit: catch possible NULL audit buffers 2013-01-11 14:54:55 -08:00
audit.c audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE 2013-06-12 16:29:45 -07:00
audit.h audit: fix mq_open and mq_unlink to add the MQ root as a hidden parent audit_names record 2013-07-09 10:33:19 -07:00
auditfilter.c audit: Fix decimal constant description 2013-07-09 10:33:19 -07:00
auditsc.c audit: fix mq_open and mq_unlink to add the MQ root as a hidden parent audit_names record 2013-07-09 10:33:19 -07:00
backtracetest.c
bounds.c
capability.c Add file_ns_capable() helper function for open-time capability checking 2013-04-14 10:06:31 -07:00
cgroup_freezer.c cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free() 2012-11-19 08:13:38 -08:00
cgroup.c cgroup: we can use simple_lookup() now 2013-07-14 17:50:23 +04:00
compat.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2013-05-01 07:21:43 -07:00
configs.c proc: Supply PDE attribute setting accessor functions 2013-05-01 17:29:18 -04:00
context_tracking.c Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-06-20 08:18:35 -10:00
cpu_pm.c
cpu.c CPU hotplug: provide a generic helper to disable/enable CPU hotplug 2013-06-12 16:29:44 -07:00
cpuset.c Merge branch 'for-3.11-cpuset' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2013-07-02 20:04:25 -07:00
crash_dump.c
cred.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2012-12-18 10:55:28 -08:00
delayacct.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c ptrace: revert "Prepare to fix racy accesses on task breakpoints" 2013-07-09 10:33:26 -07:00
extable.c extable: Flip the sorting message 2013-04-15 13:25:16 +02:00
fork.c mm: remove free_area_cache 2013-07-10 18:11:34 -07:00
freezer.c freezer: skip waking up tasks with PF_FREEZER_SKIP set 2013-05-12 14:16:22 +02:00
futex_compat.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2013-02-23 18:50:11 -08:00
futex.c futex: Use freezable blocking call 2013-06-25 23:11:19 +02:00
groups.c
hrtimer.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-07-06 14:09:38 -07:00
hung_task.c
irq_work.c Merge branch 'nohz/printk-v8' into irq/core 2013-02-05 00:48:46 +01:00
itimer.c
jump_label.c
kallsyms.c kernel: kallsyms: memory override issue, need check destination buffer length 2013-04-15 15:17:26 +09:30
kcmp.c kcmp: include linux/ptrace.h 2012-12-20 17:40:19 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking: Fix copy/paste errors of "ARCH_INLINE_*_UNLOCK_BH" 2013-05-28 08:50:00 +02:00
Kconfig.preempt
kexec.c kexec: Use min() and min_t() to simplify logic 2013-04-30 17:04:07 -07:00
kmod.c usermodehelper: kill the sub_info->path[0] check 2013-07-03 16:08:02 -07:00
kprobes.c kprobes: handle empty/invalid input to debugfs "enabled" file 2013-07-03 16:07:46 -07:00
ksysfs.c Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-12-11 18:10:49 -08:00
kthread.c kthread: implement probe_kthread_data() 2013-04-30 17:04:02 -07:00
latencytop.c
lglock.c
lockdep_internals.h
lockdep_proc.c lockdep: Use KSYM_NAME_LEN'ed buffer for __get_key_name() 2012-10-24 12:39:09 +02:00
lockdep_states.h
lockdep.c lockdep: remove task argument from debug_check_no_locks_held 2013-05-12 14:16:21 +02:00
Makefile reboot: move shutdown/reboot related functions to kernel/reboot.c 2013-07-09 10:33:29 -07:00
modsign_certificate.S CONFIG_SYMBOL_PREFIX: cleanup. 2013-03-15 15:09:43 +10:30
modsign_pubkey.c keys: use keyring_alloc() to create module signing keyring 2012-12-20 17:40:21 -08:00
module_signing.c MODSIGN: Don't use enum-type bitfields in module signature info block 2012-12-05 11:27:24 +10:30
module-internal.h MODSIGN: Move the magic string to the end of a module and eliminate the search 2012-10-19 17:30:40 -07:00
module.c Nothing interesting. Except the most embarrassing bugfix ever. But let's 2013-07-10 14:51:41 -07:00
mutex-debug.c
mutex-debug.h
mutex.c mutex: Move ww_mutex definitions to ww_mutex.h 2013-07-12 12:07:46 +02:00
mutex.h
notifier.c
nsproxy.c proc: Split the namespace stuff out into linux/proc_ns.h 2013-05-01 17:29:39 -04:00
padata.c padata: use __this_cpu_read per-cpu helper 2012-12-06 17:16:23 +08:00
panic.c The majority of the changes here are cleanups for the large changes that 2013-07-11 09:02:09 -07:00
params.c There is no /sys/parameters 2013-07-02 15:38:19 +09:30
pid_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
pid.c kernel/pid.c: move statement 2013-07-03 16:08:05 -07:00
posix-cpu-timers.c posix_timers: fix racy timer delta caching on task exit 2013-07-03 16:54:42 +02:00
posix-timers.c posix-timers: Remove unused variable 2013-04-18 12:51:19 +02:00
printk.c Merge branch 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-07-10 18:14:24 -07:00
profile.c proc: Supply PDE attribute setting accessor functions 2013-05-01 17:29:18 -04:00
ptrace.c ptrace: PTRACE_DETACH should do flush_ptrace_hw_breakpoint(child) 2013-07-09 10:33:26 -07:00
range.c range: Do not add new blank slot with add_range_with_merge 2013-06-18 11:32:10 -05:00
rcu.h rcu: Provide RCU CPU stall warnings for tiny RCU 2013-01-28 22:06:21 -08:00
rcupdate.c Merge branches 'cbnum.2013.06.10a', 'doc.2013.06.10a', 'fixes.2013.06.10a', 'srcu.2013.06.10a' and 'tiny.2013.06.10a' into HEAD 2013-06-10 13:46:44 -07:00
rcutiny_plugin.h rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs 2013-06-10 13:45:53 -07:00
rcutiny.c rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs 2013-06-10 13:45:53 -07:00
rcutorture.c rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw(). 2013-06-10 13:45:25 -07:00
rcutree_plugin.h Merge branches 'cbnum.2013.06.10a', 'doc.2013.06.10a', 'fixes.2013.06.10a', 'srcu.2013.06.10a' and 'tiny.2013.06.10a' into HEAD 2013-06-10 13:46:44 -07:00
rcutree_trace.c rcutrace: single_open() leaks 2013-05-05 00:16:35 -04:00
rcutree.c drivers: avoid parsing names as kthread_run() format strings 2013-07-03 16:07:41 -07:00
rcutree.h rcu: Drive quiescent-state-forcing delay from HZ 2013-06-10 13:44:56 -07:00
reboot.c reboot: move arch/x86 reboot= handling to generic kernel 2013-07-09 10:33:29 -07:00
relay.c Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-block 2013-05-08 10:13:35 -07:00
res_counter.c res_counter: return amount of charges after res_counter_uncharge() 2012-12-18 15:02:12 -08:00
resource.c kernel/resource.c: remove the unneeded assignment in function __find_resource 2013-07-03 16:08:06 -07:00
rtmutex_common.h
rtmutex-debug.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
rtmutex-debug.h
rtmutex-tester.c locking/rtmutex/tester: Set correct permissions on sysfs files 2013-04-10 14:48:37 +02:00
rtmutex.c rtmutex: Document rt_mutex_adjust_prio_chain() 2013-05-28 09:23:52 +02:00
rtmutex.h
rwsem.c Revert "rw_semaphore: remove up/down_read_non_owner" 2013-03-23 15:53:52 -07:00
seccomp.c seccomp: allow BPF_XOR based ALU instructions. 2013-03-26 11:07:19 +11:00
semaphore.c semaphore: use `bool' type for semaphore_waiter's up 2013-04-30 17:04:08 -07:00
signal.c sigtimedwait: use freezable blocking call 2013-05-12 14:16:23 +02:00
smp.c kernel/smp.c: cleanups 2013-04-30 17:04:03 -07:00
smpboot.c kthread: Prevent unpark race which puts threads on the wrong cpu 2013-04-12 14:18:43 +02:00
smpboot.h
softirq.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-07-02 16:14:35 -07:00
spinlock.c
srcu.c srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock() 2013-02-07 15:19:36 -08:00
stacktrace.c
stop_machine.c stop_machine: Mark per cpu stopper enabled early 2013-02-26 22:25:17 +01:00
sys_ni.c unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE 2013-05-09 13:46:38 -04:00
sys.c reboot: move shutdown/reboot related functions to kernel/reboot.c 2013-07-09 10:33:29 -07:00
sysctl_binary.c kernel: remove unnecessary head file 2013-06-26 18:01:46 +09:00
sysctl.c Merge branch 'linus' into timers/urgent 2013-07-12 12:34:42 +02:00
task_work.c
taskstats.c taskstats: cgroupstats_user_cmd() may leak on error 2012-10-06 03:05:31 +09:00
test_kprobes.c kernel/: rename random32() to prandom_u32() 2013-04-29 18:28:42 -07:00
time.c sched: Rename sched.c as sched/core.c in comments and Documentation 2013-06-19 12:58:42 +02:00
timeconst.bc kernel: Replace timeconst.pl with a bc script 2013-02-16 23:17:25 +01:00
timer.c timer: Fix jiffies wrap behavior of round_jiffies_common() 2013-06-28 17:10:11 +02:00
tracepoint.c Tracing updates for Linux 3.10 2013-04-29 13:55:38 -07:00
tsacct.c cputime: Use accessors to read task cputime stats 2013-01-27 19:23:31 +01:00
uid16.c make SYSCALL_DEFINE<n>-generated wrappers do asmlinkage_protect 2013-03-03 22:58:33 -05:00
up.c
user_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
user-return-notifier.c hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
user.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
utsname_sysctl.c kernel/utsname_sysctl.c: put get/get_uts() into CONFIG_PROC_SYSCTL code block 2013-02-27 19:10:22 -08:00
utsname.c proc: Split the namespace stuff out into linux/proc_ns.h 2013-05-01 17:29:39 -04:00
wait.c Add wait_on_atomic_t() and wake_up_atomic_t() 2013-05-15 13:50:38 +01:00
watchdog.c watchdog: Boot-disable by default on full dynticks 2013-06-20 15:46:32 +02:00
workqueue_internal.h sched: Rename sched.c as sched/core.c in comments and Documentation 2013-06-19 12:58:42 +02:00
workqueue.c Merge branch 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2013-07-02 19:53:30 -07:00