[folded-merged] mm-add-kernel-electric-fence-infrastructure-fix-3.patch removed from -mm tree

[folded-merged] mm-add-kernel-electric-fence-infrastructure-fix-3.patch removed from -mm tree

[akpm]

The patch titled
     Subject: kfence: fix potential deadlock due to wake_up()
has been removed from the -mm tree.  Its filename was
     mm-add-kernel-electric-fence-infrastructure-fix-3.patch

This patch was dropped because it was folded into mm-add-kernel-electric-fence-infrastructure.patch

------------------------------------------------------
From: Marco Elver <elver@google.com>
Subject: kfence: fix potential deadlock due to wake_up()

Lockdep reports that we may deadlock when calling wake_up() in
__kfence_alloc(), because we may already hold base->lock.  This can happen
if debug objects are enabled:

    ...
    __kfence_alloc+0xa0/0xbc0 mm/kfence/core.c:710
    kfence_alloc include/linux/kfence.h:108 [inline]
    ...
    kmem_cache_zalloc include/linux/slab.h:672 [inline]
    fill_pool+0x264/0x5c0 lib/debugobjects.c:171
    __debug_object_init+0x7a/0xd10 lib/debugobjects.c:560
    debug_object_init lib/debugobjects.c:615 [inline]
    debug_object_activate+0x32c/0x3e0 lib/debugobjects.c:701
    debug_timer_activate kernel/time/timer.c:727 [inline]
    __mod_timer+0x77d/0xe30 kernel/time/timer.c:1048
    ...

Therefore, switch to an open-coded wait loop.  The difference to before is
that the waiter wakes up and rechecks the condition after 1 jiffy;
however, given the infrequency of kfence allocations, the difference is
insignificant.

Link: https://lkml.kernel.org/r/000000000000c0645805b7f982e4@google.com
Link: https://lkml.kernel.org/r/20210104130749.1768991-1-elver@google.com
Reported-by: syzbot+8983d6d4f7df556be565@syzkaller.appspotmail.com
Signed-off-by: Marco Elver <elver@google.com>
Suggested-by: Hillf Danton <hdanton@sina.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kfence/core.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/mm/kfence/core.c~mm-add-kernel-electric-fence-infrastructure-fix-3
+++ a/mm/kfence/core.c
@@ -94,9 +94,6 @@ DEFINE_STATIC_KEY_FALSE(kfence_allocatio
 /* Gates the allocation, ensuring only one succeeds in a given period. */
 static atomic_t allocation_gate = ATOMIC_INIT(1);
 
-/* Wait queue to wake up allocation-gate timer task. */
-static DECLARE_WAIT_QUEUE_HEAD(allocation_wait);
-
 /* Statistics counters for debugfs. */
 enum kfence_counter_id {
 	KFENCE_COUNTER_ALLOCATED,
@@ -582,6 +579,8 @@ late_initcall(kfence_debugfs_init);
 static struct delayed_work kfence_timer;
 static void toggle_allocation_gate(struct work_struct *work)
 {
+	unsigned long end_wait;
+
 	if (!READ_ONCE(kfence_enabled))
 		return;
 
@@ -592,7 +591,14 @@ static void toggle_allocation_gate(struc
 	 * Await an allocation. Timeout after 1 second, in case the kernel stops
 	 * doing allocations, to avoid stalling this worker task for too long.
 	 */
-	wait_event_timeout(allocation_wait, atomic_read(&allocation_gate) != 0, HZ);
+	end_wait = jiffies + HZ;
+	do {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (atomic_read(&allocation_gate) != 0)
+			break;
+		schedule_timeout(1);
+	} while (time_before(jiffies, end_wait));
+	__set_current_state(TASK_RUNNING);
 
 	/* Disable static key and reset timer. */
 	static_branch_disable(&kfence_allocation_key);
@@ -703,7 +709,6 @@ void *__kfence_alloc(struct kmem_cache *
 	 */
 	if (atomic_read(&allocation_gate) || atomic_inc_return(&allocation_gate) > 1)
 		return NULL;
-	wake_up(&allocation_wait);
 
 	if (!READ_ONCE(kfence_enabled))
 		return NULL;
_

Patches currently in -mm which might be from elver@google.com are

mm-add-kernel-electric-fence-infrastructure.patch
mm-add-kernel-electric-fence-infrastructure-fix-4.patch
mm-add-kernel-electric-fence-infrastructure-fix-5.patch
x86-kfence-enable-kfence-for-x86-fix.patch
arm64-kfence-enable-kfence-for-arm64.patch
arm64-kfence-enable-kfence-for-arm64-fix.patch
kfence-use-pt_regs-to-generate-stack-trace-on-faults.patch
kfence-documentation-add-kfence-documentation.patch
kfence-documentation-add-kfence-documentation-fix.patch
kfence-add-test-suite.patch
kfence-add-test-suite-fix.patch
kfence-add-test-suite-fix-2.patch
maintainers-add-entry-for-kfence.patch
kfence-report-sensitive-information-based-on-no_hash_pointers.patch