Hi!
On Wed 2011-05-18 16:29:35, Russell King - ARM Linux wrote:
> On Wed, May 18, 2011 at 05:18:38PM +0200, Pavel Herrmann wrote:
> > spi_sync call uses its spi_message parameter to keep completion information,
> > having this structure static is not thread-safe, potentially causing one
> > thread having pointers to memory on or above other threads stack. use
> > per-call spi_message on stack to fix this
>
> I assume this has not been tested with DMA debugging enabled.
>
> The DMA API does not like mapping memory from the stack, which is what
> you're potentially doing with this:
In some other mail, you said "just add the locking". Pavel H.
actually produced patch doing so...
From: Pavel Herrmann <morpheus.i...@gmail.com>
To: Marek Vasut <marek.va...@gmail.com>
>From 14063b017123233a8b56d6706a9ff046a791eaf4 Mon Sep 17 00:00:00 2001
From: Pavel Herrmann <morpheus.i...@gmail.com>
Date: Mon, 16 May 2011 14:18:18 +0200
Subject: [PATCH] Fix NULL pointer exception in max1111
Signed-off-by: Pavel Herrmann <morpheus.i...@gmail.com>
---
drivers/hwmon/max1111.c | 16 ++++++++++++++++
1 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
index 12a54aa..7be50e5 100644
--- a/drivers/hwmon/max1111.c
+++ b/drivers/hwmon/max1111.c
@@ -40,6 +40,7 @@ struct max1111_data {
struct spi_transfer xfer[2];
uint8_t *tx_buf;
uint8_t *rx_buf;
+ struct mutex msg_lock_mutex;
};
static int max1111_read(struct device *dev, int channel)
@@ -48,6 +49,11 @@ static int max1111_read(struct device *dev, int channel)
uint8_t v1, v2;
int err;
+ /* spi_sync requires data not to be freed before function returns
+ * for static data, any access is dangerous, use locks
+ */
+ mutex_lock(&data->msg_lock_mutex);
+
data->tx_buf[0] = (channel << MAX1111_CTRL_SEL_SH) |
MAX1111_CTRL_PD0 | MAX1111_CTRL_PD1 |
MAX1111_CTRL_SGL | MAX1111_CTRL_UNI | MAX1111_CTRL_STR;
@@ -55,12 +61,15 @@ static int max1111_read(struct device *dev, int channel)
err = spi_sync(data->spi, &data->msg);
if (err < 0) {
dev_err(dev, "spi_sync failed with %d\n", err);
+ mutex_unlock(&data->msg_lock_mutex);
return err;
}
v1 = data->rx_buf[0];
v2 = data->rx_buf[1];
+ mutex_unlock(&data->msg_lock_mutex);
+
if ((v1 & 0xc0) || (v2 & 0x3f))
return -EINVAL;
@@ -138,6 +147,8 @@ static int setup_transfer(struct max1111_data *data)
return -ENOMEM;
}
+ mutex_lock(&data->msg_lock_mutex);
+
m = &data->msg;
x = &data->xfer[0];
@@ -152,6 +163,8 @@ static int setup_transfer(struct max1111_data *data)
x->len = 2;
spi_message_add_tail(x, m);
+ mutex_unlock(&data->msg_lock_mutex);
+
return 0;
}
@@ -172,6 +185,8 @@ static int __devinit max1111_probe(struct spi_device *spi)
return -ENOMEM;
}
+ mutex_init(&data->msg_lock_mutex);
+
err = setup_transfer(data);
if (err)
goto err_free_data;
@@ -213,6 +228,7 @@ static int __devexit max1111_remove(struct spi_device *spi)
hwmon_device_unregister(data->hwmon_dev);
sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group);
+ mutex_destroy(data->msg_lock_mutex);
kfree(data->rx_buf);
kfree(data->tx_buf);
kfree(data);
--
1.7.5.rc1
----- End forwarded message -----
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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