2019-12-19 10:36:24

by Jia-Ju Bai

Subject: [PATCH v2] media: sti: bdisp: fix a possible sleep-in-atomic-context bug in bdisp_device_run()

The driver may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:

drivers/media/platform/sti/bdisp/bdisp-hw.c, 385:
msleep in bdisp_hw_reset
drivers/media/platform/sti/bdisp/bdisp-v4l2.c, 341:
bdisp_hw_reset in bdisp_device_run
drivers/media/platform/sti/bdisp/bdisp-v4l2.c, 317:
_raw_spin_lock_irqsave in bdisp_device_run

To fix this bug, msleep() is replaced with udelay().

This bug is found by a static analysis tool STCheck written by myself.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
v2:
* Use udelay() instead of mdelay().
Thank Fabien for good advice.

---
drivers/media/platform/sti/bdisp/bdisp-hw.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/sti/bdisp/bdisp-hw.c b/drivers/media/platform/sti/bdisp/bdisp-hw.c
index 4372abbb5950..a74e9fd65238 100644
--- a/drivers/media/platform/sti/bdisp/bdisp-hw.c
+++ b/drivers/media/platform/sti/bdisp/bdisp-hw.c
@@ -14,8 +14,8 @@
#define MAX_SRC_WIDTH 2048

/* Reset & boot poll config */
-#define POLL_RST_MAX 50
-#define POLL_RST_DELAY_MS 20
+#define POLL_RST_MAX 500
+#define POLL_RST_DELAY_MS 2

enum bdisp_target_plan {
BDISP_RGB,
@@ -382,7 +382,7 @@ int bdisp_hw_reset(struct bdisp_dev *bdisp)
for (i = 0; i < POLL_RST_MAX; i++) {
if (readl(bdisp->regs + BLT_STA1) & BLT_STA1_IDLE)
break;
- msleep(POLL_RST_DELAY_MS);
+ udelay(POLL_RST_DELAY_MS * 1000);
}
if (i == POLL_RST_MAX)
dev_err(bdisp->dev, "Reset timeout\n");
--
2.17.1

2019-12-19 11:15:30

by Fabien DESSENNE

Subject: Re: [PATCH v2] media: sti: bdisp: fix a possible sleep-in-atomic-context bug in bdisp_device_run()

Thank you!


On 19/12/2019 11:34 AM, Jia-Ju Bai wrote:
> The driver may sleep while holding a spinlock.
> The function call path (from bottom to top) in Linux 4.19 is:
>
> drivers/media/platform/sti/bdisp/bdisp-hw.c, 385:
> msleep in bdisp_hw_reset
> drivers/media/platform/sti/bdisp/bdisp-v4l2.c, 341:
> bdisp_hw_reset in bdisp_device_run
> drivers/media/platform/sti/bdisp/bdisp-v4l2.c, 317:
> _raw_spin_lock_irqsave in bdisp_device_run
>
> To fix this bug, msleep() is replaced with udelay().
>
> This bug is found by a static analysis tool STCheck written by myself.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>


Reviewed-by: Fabien Dessenne <[email protected]>


> ---
> v2:
> * Use udelay() instead of mdelay().
> Thank Fabien for good advice.
>
> ---
> drivers/media/platform/sti/bdisp/bdisp-hw.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/sti/bdisp/bdisp-hw.c b/drivers/media/platform/sti/bdisp/bdisp-hw.c
> index 4372abbb5950..a74e9fd65238 100644
> --- a/drivers/media/platform/sti/bdisp/bdisp-hw.c
> +++ b/drivers/media/platform/sti/bdisp/bdisp-hw.c
> @@ -14,8 +14,8 @@
> #define MAX_SRC_WIDTH 2048
>
> /* Reset & boot poll config */
> -#define POLL_RST_MAX 50
> -#define POLL_RST_DELAY_MS 20
> +#define POLL_RST_MAX 500
> +#define POLL_RST_DELAY_MS 2
>
> enum bdisp_target_plan {
> BDISP_RGB,
> @@ -382,7 +382,7 @@ int bdisp_hw_reset(struct bdisp_dev *bdisp)
> for (i = 0; i < POLL_RST_MAX; i++) {
> if (readl(bdisp->regs + BLT_STA1) & BLT_STA1_IDLE)
> break;
> - msleep(POLL_RST_DELAY_MS);
> + udelay(POLL_RST_DELAY_MS * 1000);
> }
> if (i == POLL_RST_MAX)
> dev_err(bdisp->dev, "Reset timeout\n");