Re: [PATCH] fix lock imbalances in /drivers/media/video/cafe_ccic.c

From: Jonathan Corbet
Date: Thu Sep 10 2009 - 11:30:14 EST


On Thu, 10 Sep 2009 18:37:34 +0000
iceberg <strakh@xxxxxxxxx> wrote:

> In ./drivers/media/video/cafe_ccic.c, in function cafe_pci_probe:
> Mutex must be unlocked before exit
> 1. On paths starting with mutex lock in line 1912, then continuing in lines:
> 1929, 1936 (goto unreg) and 1940 (goto iounmap) .
> 2. On path starting in line 1971 mutex lock, and then continuing in line 1978
> (goto out_smbus) mutex.

That's a definite bug, but I hate all those unlocks in the error
branches. As it happens, we don't really need the mutex until the
device has been exposed to the rest of the kernel, so I propose the
following as a better patch.

Thanks for pointing this out,

jon

---
Fix a mutex leak

Certain error exits from cafe_pci_probe() can leave the camera mutex
locked. For much of the time, we didn't need the mutex anyway; take it out
and add an unlock in the path where it is needed.

Reported-by: Alexander Strakh <strakh@xxxxxxxxx>
Signed-off-by: Jonathan Corbet <corbet@xxxxxxx>
---
drivers/media/video/cafe_ccic.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/media/video/cafe_ccic.c b/drivers/media/video/cafe_ccic.c
index c4d181d..0f62b5e 100644
--- a/drivers/media/video/cafe_ccic.c
+++ b/drivers/media/video/cafe_ccic.c
@@ -1909,7 +1909,6 @@ static int cafe_pci_probe(struct pci_dev *pdev,
goto out_free;

mutex_init(&cam->s_mutex);
- mutex_lock(&cam->s_mutex);
spin_lock_init(&cam->dev_lock);
cam->state = S_NOTREADY;
cafe_set_config_needed(cam, 1);
@@ -1949,7 +1948,6 @@ static int cafe_pci_probe(struct pci_dev *pdev,
* because the sensor could attach in this call chain, leading to
* unsightly deadlocks.
*/
- mutex_unlock(&cam->s_mutex); /* attach can deadlock */
ret = cafe_smbus_setup(cam);
if (ret)
goto out_freeirq;
@@ -1991,6 +1989,7 @@ static int cafe_pci_probe(struct pci_dev *pdev,
return 0;

out_smbus:
+ mutex_unlock(&cam->s_mutex);
cafe_smbus_shutdown(cam);
out_freeirq:
cafe_ctlr_power_down(cam);
--
1.6.2.5

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