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authorIago Abal <mail@iagoabal.eu>2017-01-11 14:00:21 +0100
committerVinod Koul <vinod.koul@intel.com>2017-01-25 15:35:11 +0530
commit91539eb1fda2d530d3b268eef542c5414e54bf1a (patch)
tree960f5ca6342ad20837aff18aad6e8ecd7da32fd6 /drivers/dma
parent6610d0edf6dc7ee97e46ab3a538a565c79d26199 (diff)
dmaengine: pl330: fix double lock
The static bug finder EBA (http://www.iagoabal.eu/eba/) reported the following double-lock bug: Double lock: 1. spin_lock_irqsave(pch->lock, flags) at pl330_free_chan_resources:2236; 2. call to function `pl330_release_channel' immediately after; 3. call to function `dma_pl330_rqcb' in line 1753; 4. spin_lock_irqsave(pch->lock, flags) at dma_pl330_rqcb:1505. I have fixed it as suggested by Marek Szyprowski. First, I have replaced `pch->lock' with `pl330->lock' in functions `pl330_alloc_chan_resources' and `pl330_free_chan_resources'. This avoids the double-lock by acquiring a different lock than `dma_pl330_rqcb'. NOTE that, as a result, `pl330_free_chan_resources' executes `list_splice_tail_init' on `pch->work_list' under lock `pl330->lock', whereas in the rest of the code `pch->work_list' is protected by `pch->lock'. I don't know if this may cause race conditions. Similarly `pch->cyclic' is written by `pl330_alloc_chan_resources' under `pl330->lock' but read by `pl330_tx_submit' under `pch->lock'. Second, I have removed locking from `pl330_request_channel' and `pl330_release_channel' functions. Function `pl330_request_channel' is only called from `pl330_alloc_chan_resources', so the lock is already held. Function `pl330_release_channel' is called from `pl330_free_chan_resources', which already holds the lock, and from `pl330_del'. Function `pl330_del' is called in an error path of `pl330_probe' and at the end of `pl330_remove', but I assume that there cannot be concurrent accesses to the protected data at those points. Signed-off-by: Iago Abal <mail@iagoabal.eu> Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/pl330.c19
1 files changed, 6 insertions, 13 deletions
diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 740bbb942594..7539f73df9e0 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -1699,7 +1699,6 @@ static bool _chan_ns(const struct pl330_dmac *pl330, int i)
static struct pl330_thread *pl330_request_channel(struct pl330_dmac *pl330)
{
struct pl330_thread *thrd = NULL;
- unsigned long flags;
int chans, i;
if (pl330->state == DYING)
@@ -1707,8 +1706,6 @@ static struct pl330_thread *pl330_request_channel(struct pl330_dmac *pl330)
chans = pl330->pcfg.num_chan;
- spin_lock_irqsave(&pl330->lock, flags);
-
for (i = 0; i < chans; i++) {
thrd = &pl330->channels[i];
if ((thrd->free) && (!_manager_ns(thrd) ||
@@ -1726,8 +1723,6 @@ static struct pl330_thread *pl330_request_channel(struct pl330_dmac *pl330)
thrd = NULL;
}
- spin_unlock_irqrestore(&pl330->lock, flags);
-
return thrd;
}
@@ -1745,7 +1740,6 @@ static inline void _free_event(struct pl330_thread *thrd, int ev)
static void pl330_release_channel(struct pl330_thread *thrd)
{
struct pl330_dmac *pl330;
- unsigned long flags;
if (!thrd || thrd->free)
return;
@@ -1757,10 +1751,8 @@ static void pl330_release_channel(struct pl330_thread *thrd)
pl330 = thrd->dmac;
- spin_lock_irqsave(&pl330->lock, flags);
_free_event(thrd, thrd->ev);
thrd->free = true;
- spin_unlock_irqrestore(&pl330->lock, flags);
}
/* Initialize the structure for PL330 configuration, that can be used
@@ -2122,20 +2114,20 @@ static int pl330_alloc_chan_resources(struct dma_chan *chan)
struct pl330_dmac *pl330 = pch->dmac;
unsigned long flags;
- spin_lock_irqsave(&pch->lock, flags);
+ spin_lock_irqsave(&pl330->lock, flags);
dma_cookie_init(chan);
pch->cyclic = false;
pch->thread = pl330_request_channel(pl330);
if (!pch->thread) {
- spin_unlock_irqrestore(&pch->lock, flags);
+ spin_unlock_irqrestore(&pl330->lock, flags);
return -ENOMEM;
}
tasklet_init(&pch->task, pl330_tasklet, (unsigned long) pch);
- spin_unlock_irqrestore(&pch->lock, flags);
+ spin_unlock_irqrestore(&pl330->lock, flags);
return 1;
}
@@ -2238,12 +2230,13 @@ static int pl330_pause(struct dma_chan *chan)
static void pl330_free_chan_resources(struct dma_chan *chan)
{
struct dma_pl330_chan *pch = to_pchan(chan);
+ struct pl330_dmac *pl330 = pch->dmac;
unsigned long flags;
tasklet_kill(&pch->task);
pm_runtime_get_sync(pch->dmac->ddma.dev);
- spin_lock_irqsave(&pch->lock, flags);
+ spin_lock_irqsave(&pl330->lock, flags);
pl330_release_channel(pch->thread);
pch->thread = NULL;
@@ -2251,7 +2244,7 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
if (pch->cyclic)
list_splice_tail_init(&pch->work_list, &pch->dmac->desc_pool);
- spin_unlock_irqrestore(&pch->lock, flags);
+ spin_unlock_irqrestore(&pl330->lock, flags);
pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
pm_runtime_put_autosuspend(pch->dmac->ddma.dev);
}