* FAILED: patch "[PATCH] ptr_ring: fix race conditions when resizing" failed to apply to 4.10-stable tree
@ 2017-03-10 7:41 gregkh
0 siblings, 0 replies; only message in thread
From: gregkh @ 2017-03-10 7:41 UTC (permalink / raw)
To: mst; +Cc: stable
The patch below does not apply to the 4.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From e71695307114335be1ed912f4a347396c2ed0e69 Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Sun, 19 Feb 2017 07:17:17 +0200
Subject: [PATCH] ptr_ring: fix race conditions when resizing
Resizing currently drops consumer lock. This can cause entries to be
reordered, which isn't good in itself. More importantly, consumer can
detect a false ring empty condition and block forever.
Further, nesting of consumer within producer lock is problematic for
tun, since it produces entries in a BH, which causes a lock order
reversal:
CPU0 CPU1
---- ----
consume:
lock(&(&r->consumer_lock)->rlock);
resize:
local_irq_disable();
lock(&(&r->producer_lock)->rlock);
lock(&(&r->consumer_lock)->rlock);
<Interrupt>
produce:
lock(&(&r->producer_lock)->rlock);
To fix, nest producer lock within consumer lock during resize,
and keep consumer lock during the whole swap operation.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 2052011bf9fb..6c70444da3b9 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -111,6 +111,11 @@ static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr)
return 0;
}
+/*
+ * Note: resize (below) nests producer lock within consumer lock, so if you
+ * consume in interrupt or BH context, you must disable interrupts/BH when
+ * calling this.
+ */
static inline int ptr_ring_produce(struct ptr_ring *r, void *ptr)
{
int ret;
@@ -242,6 +247,11 @@ static inline void *__ptr_ring_consume(struct ptr_ring *r)
return ptr;
}
+/*
+ * Note: resize (below) nests producer lock within consumer lock, so if you
+ * call this in interrupt or BH context, you must disable interrupts/BH when
+ * producing.
+ */
static inline void *ptr_ring_consume(struct ptr_ring *r)
{
void *ptr;
@@ -357,7 +367,7 @@ static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue,
void **old;
void *ptr;
- while ((ptr = ptr_ring_consume(r)))
+ while ((ptr = __ptr_ring_consume(r)))
if (producer < size)
queue[producer++] = ptr;
else if (destroy)
@@ -372,6 +382,12 @@ static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue,
return old;
}
+/*
+ * Note: producer lock is nested within consumer lock, so if you
+ * resize you must make sure all uses nest correctly.
+ * In particular if you consume ring in interrupt or BH context, you must
+ * disable interrupts/BH when doing so.
+ */
static inline int ptr_ring_resize(struct ptr_ring *r, int size, gfp_t gfp,
void (*destroy)(void *))
{
@@ -382,17 +398,25 @@ static inline int ptr_ring_resize(struct ptr_ring *r, int size, gfp_t gfp,
if (!queue)
return -ENOMEM;
- spin_lock_irqsave(&(r)->producer_lock, flags);
+ spin_lock_irqsave(&(r)->consumer_lock, flags);
+ spin_lock(&(r)->producer_lock);
old = __ptr_ring_swap_queue(r, queue, size, gfp, destroy);
- spin_unlock_irqrestore(&(r)->producer_lock, flags);
+ spin_unlock(&(r)->producer_lock);
+ spin_unlock_irqrestore(&(r)->consumer_lock, flags);
kfree(old);
return 0;
}
+/*
+ * Note: producer lock is nested within consumer lock, so if you
+ * resize you must make sure all uses nest correctly.
+ * In particular if you consume ring in interrupt or BH context, you must
+ * disable interrupts/BH when doing so.
+ */
static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, int nrings,
int size,
gfp_t gfp, void (*destroy)(void *))
@@ -412,10 +436,12 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, int nrings,
}
for (i = 0; i < nrings; ++i) {
- spin_lock_irqsave(&(rings[i])->producer_lock, flags);
+ spin_lock_irqsave(&(rings[i])->consumer_lock, flags);
+ spin_lock(&(rings[i])->producer_lock);
queues[i] = __ptr_ring_swap_queue(rings[i], queues[i],
size, gfp, destroy);
- spin_unlock_irqrestore(&(rings[i])->producer_lock, flags);
+ spin_unlock(&(rings[i])->producer_lock);
+ spin_unlock_irqrestore(&(rings[i])->consumer_lock, flags);
}
for (i = 0; i < nrings; ++i)
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2017-03-10 7:41 FAILED: patch "[PATCH] ptr_ring: fix race conditions when resizing" failed to apply to 4.10-stable tree gregkh
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