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Message-Id: <20090722170226.c5becf38.akpm@linux-foundation.org>
Date: Wed, 22 Jul 2009 17:02:26 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc: airlied@...hat.com, catalin.marinas@....com, airlied@...il.com,
linux-kernel@...r.kernel.org, eric@...olt.net
Subject: Re: Memory leak issues in drm
On Thu, 16 Jul 2009 12:39:18 +0530
Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> On Thu, 2009-07-16 at 10:37 +0530, Jaswinder Singh Rajput wrote:
> > On linus tree, while investigating kmemleak issues in drm :
> >
> > unreferenced object 0xf571dea0 (size 32):
> > comm "Xorg", pid 1992, jiffies 4294703188
> > backtrace:
> > [<c1096655>] create_object+0x140/0x210
> > [<c10967f2>] kmemleak_alloc+0x25/0x4b
> > [<c1093b63>] __kmalloc+0xcb/0x153
> > [<c11ae939>] drm_setversion+0x154/0x1f6
> > [<c11ad0b1>] drm_ioctl+0x211/0x296
> > [<c10a2dc9>] vfs_ioctl+0x50/0x69
> > [<c10a3321>] do_vfs_ioctl+0x49b/0x4d5
> > [<c10a3387>] sys_ioctl+0x2c/0x45
> > [<c1002988>] sysenter_do_call+0x12/0x36
> > [<ffffffff>] 0xffffffff
> >
>
> This fixes above memory leak in drm because it was allocating again on
> dev->devname without freeing previous instance and more memory related
> issues, hope this will be helpful:
>
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 9b9ff46..b39ab86 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -96,25 +96,36 @@ int drm_setunique(struct drm_device *dev, void *data,
drm_setunique() is pretty crappy. It has a number of places where it
does some resource freeing and then a `return' and other places where
it does the usual `goto out_free' thing.
I do think that converting this function to the usual
single-return-statement model would simplify it and would reduce the
chances of additional resource leaks being added in the future.
The basic pattern (which is applicable here) is:
foo()
{
if (!simple test)
return -EFOO;
if (!simple_test_2)
return -EBAR;
foo = allocate_something();
if (test3)
goto fail_foo;
bar = allocate_something_else();
if (test4)
goto fail_bar;
...
return 0; /* success */
fail_bar:
deallocate(bar);
fail_foo:
deallocate(foo);
return err;
}
> master->unique = kmalloc(master->unique_size, GFP_KERNEL);
> if (!master->unique)
> return -ENOMEM;
> - if (copy_from_user(master->unique, u->unique, master->unique_len))
> + if (copy_from_user(master->unique, u->unique, master->unique_len)) {
> + kfree(master->unique);
> + master->unique_len = 0;
> return -EFAULT;
> + }
>
> master->unique[master->unique_len] = '\0';
>
> + /* Free previous dev->devname, if exists */
> + if (dev->devname)
> + kfree(dev->devname);
kfree(NULL) is legal and will simplify and shorten the code here.
> dev->devname = kmalloc(strlen(dev->driver->pci_driver.name) +
> strlen(master->unique) + 2, GFP_KERNEL);
> - if (!dev->devname)
> + if (!dev->devname) {
> + kfree(master->unique);
> + master->unique_len = 0;
> return -ENOMEM;
> + }
>
> sprintf(dev->devname, "%s@%s", dev->driver->pci_driver.name,
> master->unique);
>
> - /* Return error if the busid submitted doesn't match the device's actual
> + /*
> + * Return error if the busid submitted doesn't match the device's actual
> * busid.
> */
> ret = sscanf(master->unique, "PCI:%d:%d:%d", &bus, &slot, &func);
> if (ret != 3)
> - return -EINVAL;
> + goto error;
> +
> domain = bus >> 8;
> bus &= 0xff;
>
> @@ -122,9 +133,15 @@ int drm_setunique(struct drm_device *dev, void *data,
> (bus != dev->pdev->bus->number) ||
> (slot != PCI_SLOT(dev->pdev->devfn)) ||
> (func != PCI_FUNC(dev->pdev->devfn)))
> - return -EINVAL;
> + goto error;
>
> return 0;
> +
> +error:
> + kfree(dev->devname);
> + kfree(master->unique);
> +
> + return -EINVAL;
> }
>
> static int drm_set_busid(struct drm_device *dev, struct drm_file *file_priv)
> @@ -136,25 +153,35 @@ static int drm_set_busid(struct drm_device *dev, struct drm_file *file_priv)
> return -EBUSY;
>
> master->unique_len = 40;
> - master->unique_size = master->unique_len;
> + master->unique_size = master->unique_len + 1;
> master->unique = kmalloc(master->unique_size, GFP_KERNEL);
> if (master->unique == NULL)
> return -ENOMEM;
>
> - len = snprintf(master->unique, master->unique_len, "pci:%04x:%02x:%02x.%d",
> + /*
> + * Using sprintf as it will return number of characters
> + * (not including the trailing '\0')
> + */
> + len = sprintf(master->unique, "pci:%04x:%02x:%02x.%d",
> drm_get_pci_domain(dev),
> dev->pdev->bus->number,
> PCI_SLOT(dev->pdev->devfn),
> PCI_FUNC(dev->pdev->devfn));
> - if (len >= master->unique_len)
> + if (len > master->unique_len)
> DRM_ERROR("buffer overflow");
> else
> master->unique_len = len;
>
> + /* Free previous dev->devname, if exists */
> + if (dev->devname)
> + kfree(dev->devname);
and here.
> dev->devname = kmalloc(strlen(dev->driver->pci_driver.name) +
> master->unique_len + 2, GFP_KERNEL);
> - if (dev->devname == NULL)
> + if (dev->devname == NULL) {
> + kfree(master->unique);
> + master->unique_len = 0;
> return -ENOMEM;
> + }
>
> sprintf(dev->devname, "%s@%s", dev->driver->pci_driver.name,
> master->unique);
>
--
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