The patch titled
sigqueue_free: fix the race with collect_signal()
has been removed from the -mm tree. Its filename was
sigqueue_free-fix-the-race-with-collect_signal.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: sigqueue_free: fix the race with collect_signal()
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Spotted by taoyue <yue.tao@xxxxxxxxxxxxx> and Jeremy Katz <jeremy.katz@xxxxxxxxxxxxx>.
collect_signal: sigqueue_free:
list_del_init(&first->list);
if (!list_empty(&q->list)) {
// not taken
}
q->flags &= ~SIGQUEUE_PREALLOC;
__sigqueue_free(first); __sigqueue_free(q);
Now, __sigqueue_free() is called twice on the same "struct sigqueue" with the
obviously bad implications.
In particular, this double free breaks the array_cache->avail logic, so the
same sigqueue could be "allocated" twice, and the bug can manifest itself via
the "impossible" BUG_ON(!SIGQUEUE_PREALLOC) in sigqueue_free/send_sigqueue.
Hopefully this can explain these mysterious bug-reports, see
http://marc.info/?t=118766926500003
http://marc.info/?t=118466273000005
Alexey Dobriyan reports this patch makes the difference for the testcase, but
nobody has an access to the application which opened the problems originally.
Also, this patch removes tasklist lock/unlock, ->siglock is enough.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: taoyue <yue.tao@xxxxxxxxxxxxx>
Cc: Jeremy Katz <jeremy.katz@xxxxxxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/signal.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff -puN kernel/signal.c~sigqueue_free-fix-the-race-with-collect_signal kernel/signal.c
--- a/kernel/signal.c~sigqueue_free-fix-the-race-with-collect_signal
+++ a/kernel/signal.c
@@ -1300,20 +1300,19 @@ struct sigqueue *sigqueue_alloc(void)
void sigqueue_free(struct sigqueue *q)
{
unsigned long flags;
+ spinlock_t *lock = ¤t->sighand->siglock;
+
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
/*
* If the signal is still pending remove it from the
- * pending queue.
+ * pending queue. We must hold ->siglock while testing
+ * q->list to serialize with collect_signal().
*/
- if (unlikely(!list_empty(&q->list))) {
- spinlock_t *lock = ¤t->sighand->siglock;
- read_lock(&tasklist_lock);
- spin_lock_irqsave(lock, flags);
- if (!list_empty(&q->list))
- list_del_init(&q->list);
- spin_unlock_irqrestore(lock, flags);
- read_unlock(&tasklist_lock);
- }
+ spin_lock_irqsave(lock, flags);
+ if (!list_empty(&q->list))
+ list_del_init(&q->list);
+ spin_unlock_irqrestore(lock, flags);
+
q->flags &= ~SIGQUEUE_PREALLOC;
__sigqueue_free(q);
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
git-dvb.patch
rt-ptracer-can-monopolize-cpu-was-cpu-hotplug-and-real-time.patch
clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch
do_sys_poll-simplify-playing-with-on-stack-data.patch
do_sys_poll-simplify-playing-with-on-stack-data-fix.patch
do_poll-return-eintr-when-signalled.patch
pi-futex-set-pf_exiting-without-taking-pi_lock.patch
do_sigaction-remove-now-unneeded-recalc_sigpending.patch
handle-the-multi-threaded-inits-exit-properly.patch
wait_task_zombie-remove-unneeded-child-signal-check.patch
wait_task_zombie-fix-2-3-races-vs-forget_original_parent.patch
exit_notify-dont-take-tasklist-for-tif_sigpending-re-targeting.patch
zap_other_threads-dont-optimize-thread_group_empty-case.patch
wait_task_zombie-dont-fight-with-non-existing-race-with-a-dying-ptracee.patch
__group_complete_signal-eliminate-unneeded-wakeup-of-group_exit_task.patch
use-erestart_restartblock-if-poll-is-interrupted-by-a-signal.patch
exec-simplify-sighand-switching.patch
exec-simplify-the-new-sighand-allocation.patch
exec-consolidate-2-fast-paths.patch
exec-rt-sub-thread-can-livelock-and-monopolize-cpu-on-exec.patch
do_sigaction-dont-worry-about-signal_pending.patch
cpu-hotplug-slab-cleanup-cpuup_callback.patch
cpu-hotplug-slab-fix-memory-leak-in-cpu-hotplug-error-path.patch
cpu-hotplug-cpu-deliver-cpu_up_canceled-only-to-notify_oked-callbacks-with-cpu_up_prepare.patch
cpu-hotplug-topology-remove-topology_dev_map.patch
cpu-hotplug-thermal_throttle-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-msr-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-cpuid-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-mce-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-intel_cacheinfo-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-intel_cacheinfo-fix-cpu-hotplug-error-handling-fix-a-section-mismatch-warning.patch
do-cpu_dead-migrating-under-read_locktasklist-instead-of-write_lock_irqtasklist.patch
migration_callcpu_dead-use-spin_lock_irq-instead-of-task_rq_lock.patch
make-access-to-tasks-nsproxy-lighter.patch
workqueue-debug-flushing-deadlocks-with-lockdep.patch
workqueue-debug-work-related-deadlocks-with-lockdep.patch
pid-namespaces-rework-forget_original_parent.patch
pid-namespaces-move-exit_task_namespaces.patch
pid-namespaces-introduce-ms_kernmount-flag.patch
pid-namespaces-prepare-proc_flust_task-to-flush-entries-from-multiple-proc-trees.patch
pid-namespaces-introduce-struct-upid.patch
pid-namespaces-add-support-for-pid-namespaces-hierarchy.patch
pid-namespaces-make-alloc_pid-free_pid-and-put_pid-work-with-struct-upid.patch
pid-namespaces-helpers-to-obtain-pid-numbers.patch
pid-namespaces-helpers-to-find-the-task-by-its-numerical-ids.patch
pid-namespaces-helpers-to-find-the-task-by-its-numerical-ids-fix.patch
pid-namespaces-move-alloc_pid-lower-in-copy_process.patch
pid-namespaces-make-proc-have-multiple-superblocks-one-for-each-namespace.patch
pid-namespaces-miscelaneous-preparations-for-pid-namespaces.patch
pid-namespaces-allow-cloning-of-new-namespace.patch
pid-namespaces-allow-cloning-of-new-namespace-fix-check-for-return-value-of-create_pid_namespace.patch
pid-namespaces-make-proc_flush_task-actually-from-entries-from-multiple-namespaces.patch
pid-namespaces-initialize-the-namespaces-proc_mnt.patch
pid-namespaces-create-a-slab-cache-for-struct-pid_namespace.patch
pid-namespaces-allow-signalling-container-init.patch
pid-namespaces-destroy-pid-namespace-on-inits-death.patch
pid-namespaces-changes-to-show-virtual-ids-to-user.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-fix-the-return-value-of-sys_set_tid_address.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-use-find_task_by_pid_ns-in-places-that-operate-with-virtual.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-use-find_task_by_pid_ns-in-places-that-operate-with-virtual-fix.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-use-find_task_by_pid_ns-in-places-that-operate-with-virtual-fix-2.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-use-find_task_by_pid_ns-in-places-that-operate-with-virtual-fix-3.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-fix.patch
pid-namespaces-remove-the-struct-pid-unneeded-fields.patch
isolate-some-explicit-usage-of-task-tgid.patch
proc-export-a-processes-resource-limits-via-proc-pid.patch
fix-tsk-exit_state-usage-resend.patch
isolate-the-explicit-usage-of-signal-pgrp.patch
hotplug-cpu-migrate-a-task-within-its-cpuset.patch
hotplug-cpu-migrate-a-task-within-its-cpuset-doc.patch
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