[PATCH v1] dmaengine: sf-pdma: pdma_desc memory leak fix

shravan kumar
2023-01-20T10:06:52Z

From: Shravan Chippa <shravan.chippa@microchip.com>

Commit b2cc5c465c2c ("dmaengine: sf-pdma: Add multithread support for a
DMA channel") changed sf_pdma_prep_dma_memcpy() to unconditionally
allocate a new sf_pdma_desc each time it is called.

The driver previously recycled descs, by checking the in_use flag, only
allocating additional descs if the existing one was in use. This logic
was removed in commit b2cc5c465c2c ("dmaengine: sf-pdma: Add multithread
support for a DMA channel"), but sf_pdma_free_desc() was not changed to
handle the new behaviour.

As a result, each time sf_pdma_prep_dma_memcpy() is called, the previous
descriptor is leaked, over time leading to memory starvation:

unreferenced object 0xffffffe008447300 (size 192):
comm "irq/39-mchp_dsc", pid 343, jiffies 4294906910 (age 981.200s)
hex dump (first 32 bytes):
00 00 00 ff 00 00 00 00 b8 c1 00 00 00 00 00 00 ................
00 00 70 08 10 00 00 00 00 00 00 c0 00 00 00 00 ..p.............
backtrace:
[<00000000064a04f4>] kmemleak_alloc+0x1e/0x28
[<00000000018927a7>] kmem_cache_alloc+0x11e/0x178
[<000000002aea8d16>] sf_pdma_prep_dma_memcpy+0x40/0x112

Add the missing kfree() to sf_pdma_free_desc(), and remove the redundant
in_use flag.

Fixes: b2cc5c465c2c ("dmaengine: sf-pdma: Add multithread support for a DMA channel")
Signed-off-by: Shravan Chippa <shravan.chippa@microchip.com>
---
drivers/dma/sf-pdma/sf-pdma.c | 3 +--
drivers/dma/sf-pdma/sf-pdma.h | 1 -
2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
index 6b524eb6bcf3..e578ad556949 100644
--- a/drivers/dma/sf-pdma/sf-pdma.c
+++ b/drivers/dma/sf-pdma/sf-pdma.c
@@ -96,7 +96,6 @@ sf_pdma_prep_dma_memcpy(struct dma_chan *dchan, dma_addr_t dest, dma_addr_t src,
if (!desc)
return NULL;

- desc->in_use = true;
desc->dirn = DMA_MEM_TO_MEM;
desc->async_tx = vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);

@@ -290,7 +289,7 @@ static void sf_pdma_free_desc(struct virt_dma_desc *vdesc)
struct sf_pdma_desc *desc;

desc = to_sf_pdma_desc(vdesc);
- desc->in_use = false;
+ kfree(desc);
}

static void sf_pdma_donebh_tasklet(struct tasklet_struct *t)
diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
index dcb3687bd5da..5c398a83b491 100644
--- a/drivers/dma/sf-pdma/sf-pdma.h
+++ b/drivers/dma/sf-pdma/sf-pdma.h
@@ -78,7 +78,6 @@ struct sf_pdma_desc {
u64 src_addr;
struct virt_dma_desc vdesc;
struct sf_pdma_chan *chan;
- bool in_use;
enum dma_transfer_direction dirn;
struct dma_async_tx_descriptor *async_tx;
};
--
2.34.1