[PATCH v2] dmaengine: stm32: Don't use %pK through printk

[PATCH v2] dmaengine: stm32: Don't use %pK through printk

[Thomas Weißschuh]

In the past %pK was preferable to %p as it would not leak raw pointer
values into the kernel log.
Since commit ad67b74d2469 ("printk: hash addresses printed with %p")
the regular %p has been improved to avoid this issue.
Furthermore, restricted pointers ("%pK") were never meant to be used
through printk(). They can still unintentionally leak raw pointers or
acquire sleeping locks in atomic contexts.

Switch to the regular pointer formatting which is safer and
easier to reason about.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
---
Changes in v2:
- Rebase onto 6.16-rc
- Pick up review from Amelie
- Fix typo in commit message
- Drop inapplicable mention of seq_file from commit message
- Link to v1: https://lore.kernel.org/r/20250407-restricted-pointers-dma-v1-1-b617dd0e293a@linutronix.de
---
 drivers/dma/stm32/stm32-dma.c  | 10 +++++-----
 drivers/dma/stm32/stm32-dma3.c | 10 +++++-----
 drivers/dma/stm32/stm32-mdma.c |  8 ++++----
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/dma/stm32/stm32-dma.c b/drivers/dma/stm32/stm32-dma.c
index 917f8e9223739af853e492d97cecac0e95e0aea3..ee9246c6888ffde2d416270f25890c04c72daff7 100644
--- a/drivers/dma/stm32/stm32-dma.c
+++ b/drivers/dma/stm32/stm32-dma.c
@@ -613,7 +613,7 @@ static void stm32_dma_start_transfer(struct stm32_dma_chan *chan)
 	reg->dma_scr |= STM32_DMA_SCR_EN;
 	stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), reg->dma_scr);
 
-	dev_dbg(chan2dev(chan), "vchan %pK: started\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: started\n", &chan->vchan);
 }
 
 static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan)
@@ -676,7 +676,7 @@ static void stm32_dma_handle_chan_paused(struct stm32_dma_chan *chan)
 
 	chan->status = DMA_PAUSED;
 
-	dev_dbg(chan2dev(chan), "vchan %pK: paused\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: paused\n", &chan->vchan);
 }
 
 static void stm32_dma_post_resume_reconfigure(struct stm32_dma_chan *chan)
@@ -728,7 +728,7 @@ static void stm32_dma_post_resume_reconfigure(struct stm32_dma_chan *chan)
 	dma_scr |= STM32_DMA_SCR_EN;
 	stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), dma_scr);
 
-	dev_dbg(chan2dev(chan), "vchan %pK: reconfigured after pause/resume\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: reconfigured after pause/resume\n", &chan->vchan);
 }
 
 static void stm32_dma_handle_chan_done(struct stm32_dma_chan *chan, u32 scr)
@@ -820,7 +820,7 @@ static void stm32_dma_issue_pending(struct dma_chan *c)
 
 	spin_lock_irqsave(&chan->vchan.lock, flags);
 	if (vchan_issue_pending(&chan->vchan) && !chan->desc && !chan->busy) {
-		dev_dbg(chan2dev(chan), "vchan %pK: issued\n", &chan->vchan);
+		dev_dbg(chan2dev(chan), "vchan %p: issued\n", &chan->vchan);
 		stm32_dma_start_transfer(chan);
 
 	}
@@ -922,7 +922,7 @@ static int stm32_dma_resume(struct dma_chan *c)
 
 	spin_unlock_irqrestore(&chan->vchan.lock, flags);
 
-	dev_dbg(chan2dev(chan), "vchan %pK: resumed\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: resumed\n", &chan->vchan);
 
 	return 0;
 }
diff --git a/drivers/dma/stm32/stm32-dma3.c b/drivers/dma/stm32/stm32-dma3.c
index 0c6c4258b19561c94f1c68f26ade16b82660ebe6..50e7106c5cb73394c1de52ad5f571f6db63750e6 100644
--- a/drivers/dma/stm32/stm32-dma3.c
+++ b/drivers/dma/stm32/stm32-dma3.c
@@ -801,7 +801,7 @@ static void stm32_dma3_chan_start(struct stm32_dma3_chan *chan)
 
 	chan->dma_status = DMA_IN_PROGRESS;
 
-	dev_dbg(chan2dev(chan), "vchan %pK: started\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: started\n", &chan->vchan);
 }
 
 static int stm32_dma3_chan_suspend(struct stm32_dma3_chan *chan, bool susp)
@@ -1452,7 +1452,7 @@ static int stm32_dma3_pause(struct dma_chan *c)
 
 	chan->dma_status = DMA_PAUSED;
 
-	dev_dbg(chan2dev(chan), "vchan %pK: paused\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: paused\n", &chan->vchan);
 
 	return 0;
 }
@@ -1465,7 +1465,7 @@ static int stm32_dma3_resume(struct dma_chan *c)
 
 	chan->dma_status = DMA_IN_PROGRESS;
 
-	dev_dbg(chan2dev(chan), "vchan %pK: resumed\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: resumed\n", &chan->vchan);
 
 	return 0;
 }
@@ -1490,7 +1490,7 @@ static int stm32_dma3_terminate_all(struct dma_chan *c)
 	spin_unlock_irqrestore(&chan->vchan.lock, flags);
 	vchan_dma_desc_free_list(&chan->vchan, &head);
 
-	dev_dbg(chan2dev(chan), "vchan %pK: terminated\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: terminated\n", &chan->vchan);
 
 	return 0;
 }
@@ -1543,7 +1543,7 @@ static void stm32_dma3_issue_pending(struct dma_chan *c)
 	spin_lock_irqsave(&chan->vchan.lock, flags);
 
 	if (vchan_issue_pending(&chan->vchan) && !chan->swdesc) {
-		dev_dbg(chan2dev(chan), "vchan %pK: issued\n", &chan->vchan);
+		dev_dbg(chan2dev(chan), "vchan %p: issued\n", &chan->vchan);
 		stm32_dma3_chan_start(chan);
 	}
 
diff --git a/drivers/dma/stm32/stm32-mdma.c b/drivers/dma/stm32/stm32-mdma.c
index e6d525901de7ecf822d218b87b95aba6bbf0a3ef..080c1c725216cb627675c372591b4c0c227c3cea 100644
--- a/drivers/dma/stm32/stm32-mdma.c
+++ b/drivers/dma/stm32/stm32-mdma.c
@@ -1187,7 +1187,7 @@ static void stm32_mdma_start_transfer(struct stm32_mdma_chan *chan)
 
 	chan->busy = true;
 
-	dev_dbg(chan2dev(chan), "vchan %pK: started\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: started\n", &chan->vchan);
 }
 
 static void stm32_mdma_issue_pending(struct dma_chan *c)
@@ -1200,7 +1200,7 @@ static void stm32_mdma_issue_pending(struct dma_chan *c)
 	if (!vchan_issue_pending(&chan->vchan))
 		goto end;
 
-	dev_dbg(chan2dev(chan), "vchan %pK: issued\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: issued\n", &chan->vchan);
 
 	if (!chan->desc && !chan->busy)
 		stm32_mdma_start_transfer(chan);
@@ -1220,7 +1220,7 @@ static int stm32_mdma_pause(struct dma_chan *c)
 	spin_unlock_irqrestore(&chan->vchan.lock, flags);
 
 	if (!ret)
-		dev_dbg(chan2dev(chan), "vchan %pK: pause\n", &chan->vchan);
+		dev_dbg(chan2dev(chan), "vchan %p: pause\n", &chan->vchan);
 
 	return ret;
 }
@@ -1261,7 +1261,7 @@ static int stm32_mdma_resume(struct dma_chan *c)
 
 	spin_unlock_irqrestore(&chan->vchan.lock, flags);
 
-	dev_dbg(chan2dev(chan), "vchan %pK: resume\n", &chan->vchan);
+	dev_dbg(chan2dev(chan), "vchan %p: resume\n", &chan->vchan);
 
 	return 0;
 }

---
base-commit: 52da431bf03b5506203bca27fe14a97895c80faf
change-id: 20250404-restricted-pointers-dma-29cf839a1a0b

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>

Re: [PATCH v2] dmaengine: stm32: Don't use %pK through printk

[Vinod Koul]

On Wed, 18 Jun 2025 09:43:34 +0200, Thomas Weißschuh wrote:
> In the past %pK was preferable to %p as it would not leak raw pointer
> values into the kernel log.
> Since commit ad67b74d2469 ("printk: hash addresses printed with %p")
> the regular %p has been improved to avoid this issue.
> Furthermore, restricted pointers ("%pK") were never meant to be used
> through printk(). They can still unintentionally leak raw pointers or
> acquire sleeping locks in atomic contexts.
> 
> [...]

Applied, thanks!

[1/1] dmaengine: stm32: Don't use %pK through printk
      commit: 6e6d3c6f0ef235a95c25385b2dad98e8ad6223eb

Best regards,
-- 
~Vinod