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Date: Fri, 11 Jan 2013 12:36:52 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Jan Beulich <JBeulich@...e.com>
Cc: Olaf Hering <olaf@...fle.de>, Jens Axboe <axboe@...nel.dk>,
xen-devel <xen-devel@...ts.xen.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen-blkback: do not leak mode property
On Thu, Dec 20, 2012 at 10:31:11AM +0000, Jan Beulich wrote:
> "be->mode" is obtained from xenbus_read(), which does a kmalloc() for
> the message body. The short string is never released, so do it along
> with freeing "be" itself, and make sure the string isn't kept when
> backend_changed() doesn't complete successfully (which made it
> desirable to slightly re-structure that function, so that the error
> cleanup can be done in one place).
applied.
>
> Reported-by: Olaf Hering <olaf@...fle.de>
> Signed-off-by: Jan Beulich <jbeulich@...e.com>
>
> ---
> drivers/block/xen-blkback/xenbus.c | 49 ++++++++++++++++++-------------------
> 1 file changed, 24 insertions(+), 25 deletions(-)
>
> --- 3.7/drivers/block/xen-blkback/xenbus.c
> +++ 3.7-xen-blkback-mode-leak/drivers/block/xen-blkback/xenbus.c
> @@ -366,6 +366,7 @@ static int xen_blkbk_remove(struct xenbu
> be->blkif = NULL;
> }
>
> + kfree(be->mode);
> kfree(be);
> dev_set_drvdata(&dev->dev, NULL);
> return 0;
> @@ -501,6 +502,7 @@ static void backend_changed(struct xenbu
> = container_of(watch, struct backend_info, backend_watch);
> struct xenbus_device *dev = be->dev;
> int cdrom = 0;
> + unsigned long handle;
> char *device_type;
>
> DPRINTK("");
> @@ -520,10 +522,10 @@ static void backend_changed(struct xenbu
> return;
> }
>
> - if ((be->major || be->minor) &&
> - ((be->major != major) || (be->minor != minor))) {
> - pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
> - be->major, be->minor, major, minor);
> + if (be->major | be->minor) {
> + if (be->major != major || be->minor != minor)
> + pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
> + be->major, be->minor, major, minor);
> return;
> }
>
> @@ -541,36 +543,33 @@ static void backend_changed(struct xenbu
> kfree(device_type);
> }
>
> - if (be->major == 0 && be->minor == 0) {
> - /* Front end dir is a number, which is used as the handle. */
> + /* Front end dir is a number, which is used as the handle. */
> + err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
> + if (err)
> + return;
>
> - char *p = strrchr(dev->otherend, '/') + 1;
> - long handle;
> - err = strict_strtoul(p, 0, &handle);
> - if (err)
> - return;
> + be->major = major;
> + be->minor = minor;
>
> - be->major = major;
> - be->minor = minor;
> -
> - err = xen_vbd_create(be->blkif, handle, major, minor,
> - (NULL == strchr(be->mode, 'w')), cdrom);
> - if (err) {
> - be->major = 0;
> - be->minor = 0;
> - xenbus_dev_fatal(dev, err, "creating vbd structure");
> - return;
> - }
> + err = xen_vbd_create(be->blkif, handle, major, minor,
> + !strchr(be->mode, 'w'), cdrom);
>
> + if (err)
> + xenbus_dev_fatal(dev, err, "creating vbd structure");
> + else {
> err = xenvbd_sysfs_addif(dev);
> if (err) {
> xen_vbd_free(&be->blkif->vbd);
> - be->major = 0;
> - be->minor = 0;
> xenbus_dev_fatal(dev, err, "creating sysfs entries");
> - return;
> }
> + }
>
> + if (err) {
> + kfree(be->mode);
> + be->mode = NULL;
> + be->major = 0;
> + be->minor = 0;
> + } else {
> /* We're potentially connected now */
> xen_update_blkif_status(be->blkif);
> }
>
>
>
> xen-blkback: do not leak mode property
>
> "be->mode" is obtained from xenbus_read(), which does a kmalloc() for
> the message body. The short string is never released, so do it along
> with freeing "be" itself, and make sure the string isn't kept when
> backend_changed() doesn't complete successfully (which made it
> desirable to slightly re-structure that function, so that the error
> cleanup can be done in one place).
>
> Reported-by: Olaf Hering <olaf@...fle.de>
> Signed-off-by: Jan Beulich <jbeulich@...e.com>
>
> ---
> drivers/block/xen-blkback/xenbus.c | 49 ++++++++++++++++++-------------------
> 1 file changed, 24 insertions(+), 25 deletions(-)
>
> --- 3.7/drivers/block/xen-blkback/xenbus.c
> +++ 3.7-xen-blkback-mode-leak/drivers/block/xen-blkback/xenbus.c
> @@ -366,6 +366,7 @@ static int xen_blkbk_remove(struct xenbu
> be->blkif = NULL;
> }
>
> + kfree(be->mode);
> kfree(be);
> dev_set_drvdata(&dev->dev, NULL);
> return 0;
> @@ -501,6 +502,7 @@ static void backend_changed(struct xenbu
> = container_of(watch, struct backend_info, backend_watch);
> struct xenbus_device *dev = be->dev;
> int cdrom = 0;
> + unsigned long handle;
> char *device_type;
>
> DPRINTK("");
> @@ -520,10 +522,10 @@ static void backend_changed(struct xenbu
> return;
> }
>
> - if ((be->major || be->minor) &&
> - ((be->major != major) || (be->minor != minor))) {
> - pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
> - be->major, be->minor, major, minor);
> + if (be->major | be->minor) {
> + if (be->major != major || be->minor != minor)
> + pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
> + be->major, be->minor, major, minor);
> return;
> }
>
> @@ -541,36 +543,33 @@ static void backend_changed(struct xenbu
> kfree(device_type);
> }
>
> - if (be->major == 0 && be->minor == 0) {
> - /* Front end dir is a number, which is used as the handle. */
> + /* Front end dir is a number, which is used as the handle. */
> + err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
> + if (err)
> + return;
>
> - char *p = strrchr(dev->otherend, '/') + 1;
> - long handle;
> - err = strict_strtoul(p, 0, &handle);
> - if (err)
> - return;
> + be->major = major;
> + be->minor = minor;
>
> - be->major = major;
> - be->minor = minor;
> -
> - err = xen_vbd_create(be->blkif, handle, major, minor,
> - (NULL == strchr(be->mode, 'w')), cdrom);
> - if (err) {
> - be->major = 0;
> - be->minor = 0;
> - xenbus_dev_fatal(dev, err, "creating vbd structure");
> - return;
> - }
> + err = xen_vbd_create(be->blkif, handle, major, minor,
> + !strchr(be->mode, 'w'), cdrom);
>
> + if (err)
> + xenbus_dev_fatal(dev, err, "creating vbd structure");
> + else {
> err = xenvbd_sysfs_addif(dev);
> if (err) {
> xen_vbd_free(&be->blkif->vbd);
> - be->major = 0;
> - be->minor = 0;
> xenbus_dev_fatal(dev, err, "creating sysfs entries");
> - return;
> }
> + }
>
> + if (err) {
> + kfree(be->mode);
> + be->mode = NULL;
> + be->major = 0;
> + be->minor = 0;
> + } else {
> /* We're potentially connected now */
> xen_update_blkif_status(be->blkif);
> }
--
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