This series fixes a number of use-after-frees in nouveau's postclose() handler. It was discovered by pointing IGT's core_hotunplug tests at a nouveau device, but the steps to reproduce it are simple:
1. Open the device file 2. Unbind the driver or remove the device 3. Close the file opened in step 1.
During the device removal, the nouveau_drm structure is de-allocated, but is dereferenced in the postclose() handler.
One obvious solution is to ensure all the operations in the postclose() handler are valid by extending the lifetime of the nouveau_drm structure. This is possible with the new devm_drm_dev_alloc() interface, but the change is somewhat invasive so I thought it best to submit that work separately.
Instead, we make use of the drm_dev_unplug() API, clean up all clients in the device removal call, and check to make sure the device has not been unplugged in the postclose() handler. While this does not enable hot-unplug support for nouveau, it's enough to avoid crashing the kernel and leads to all the core_hotunplug tests to pass.
Jeremy Cline (3): drm/nouveau: use drm_dev_unplug() during device removal drm/nouveau: Add a dedicated mutex for the clients list drm/nouveau: clean up all clients on device removal
drivers/gpu/drm/nouveau/nouveau_drm.c | 39 +++++++++++++++++++++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 ++++ 2 files changed, 39 insertions(+), 5 deletions(-)
Nouveau does not currently support hot-unplugging, but it still makes sense to switch from drm_dev_unregister() to drm_dev_unplug(). drm_dev_unplug() calls drm_dev_unregister() after marking the device as unplugged, but only after any device critical sections are finished.
Since nouveau isn't using drm_dev_enter() and drm_dev_exit(), there are no critical sections so this is nearly functionally equivalent. However, the DRM layer does check to see if the device is unplugged, and if it is returns appropriate error codes.
In the future nouveau can add critical sections in order to truly support hot-unplugging.
Signed-off-by: Jeremy Cline jcline@redhat.com --- drivers/gpu/drm/nouveau/nouveau_drm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index d141a5f004af..4fe4d664c5f2 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -792,7 +792,7 @@ nouveau_drm_device_remove(struct drm_device *dev) struct nvkm_client *client; struct nvkm_device *device;
- drm_dev_unregister(dev); + drm_dev_unplug(dev);
dev->irq_enabled = false; client = nvxx_client(&drm->client.base);
Rather than protecting the nouveau_drm clients list with the lock within the "client" nouveau_cli, add a dedicated lock to serialize access to the list. This is both clearer and necessary to avoid lockdep being upset with us when we need to iterate through all the clients in the list and potentially lock their mutex, which is the same class as the lock protecting the entire list.
Signed-off-by: Jeremy Cline jcline@redhat.com --- drivers/gpu/drm/nouveau/nouveau_drm.c | 9 +++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 +++++ 2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index 4fe4d664c5f2..d182b877258a 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -557,6 +557,7 @@ nouveau_drm_device_init(struct drm_device *dev) nvkm_dbgopt(nouveau_debug, "DRM");
INIT_LIST_HEAD(&drm->clients); + mutex_init(&drm->clients_lock); spin_lock_init(&drm->tile.lock);
/* workaround an odd issue on nvc1 by disabling the device's @@ -1089,9 +1090,9 @@ nouveau_drm_open(struct drm_device *dev, struct drm_file *fpriv)
fpriv->driver_priv = cli;
- mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_add(&cli->head, &drm->clients); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock);
done: if (ret && cli) { @@ -1117,9 +1118,9 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) nouveau_abi16_fini(cli->abi16); mutex_unlock(&cli->mutex);
- mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_del(&cli->head); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock);
nouveau_cli_fini(cli); kfree(cli); diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h index 9d04d1b36434..550e5f335146 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drv.h +++ b/drivers/gpu/drm/nouveau/nouveau_drv.h @@ -141,6 +141,11 @@ struct nouveau_drm {
struct list_head clients;
+ /** + * @clients_lock: Protects access to the @clients list of &struct nouveau_cli. + */ + struct mutex clients_lock; + u8 old_pm_cap;
struct {
On Tue, 2020-11-03 at 14:49 -0500, Jeremy Cline wrote:
Rather than protecting the nouveau_drm clients list with the lock within the "client" nouveau_cli, add a dedicated lock to serialize access to the list. This is both clearer and necessary to avoid lockdep being upset with us when we need to iterate through all the clients in the list and potentially lock their mutex, which is the same class as the lock protecting the entire list.
Signed-off-by: Jeremy Cline jcline@redhat.com
drivers/gpu/drm/nouveau/nouveau_drm.c | 9 +++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 +++++ 2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index 4fe4d664c5f2..d182b877258a 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -557,6 +557,7 @@ nouveau_drm_device_init(struct drm_device *dev) nvkm_dbgopt(nouveau_debug, "DRM"); INIT_LIST_HEAD(&drm->clients); + mutex_init(&drm->clients_lock);
Looks like you forgot to hook up mutex_destroy() somewhere. Note there's actually plenty of code in nouveau right now that forgets to do this, but at some point we should probably fix that and avoid adding more spots where there's no mutex_destroy().
spin_lock_init(&drm->tile.lock); /* workaround an odd issue on nvc1 by disabling the device's @@ -1089,9 +1090,9 @@ nouveau_drm_open(struct drm_device *dev, struct drm_file *fpriv) fpriv->driver_priv = cli; - mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_add(&cli->head, &drm->clients); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock); done: if (ret && cli) { @@ -1117,9 +1118,9 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) nouveau_abi16_fini(cli->abi16); mutex_unlock(&cli->mutex); - mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_del(&cli->head); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock); nouveau_cli_fini(cli); kfree(cli); diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h index 9d04d1b36434..550e5f335146 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drv.h +++ b/drivers/gpu/drm/nouveau/nouveau_drv.h @@ -141,6 +141,11 @@ struct nouveau_drm { struct list_head clients; + /** + * @clients_lock: Protects access to the @clients list of &struct nouveau_cli. + */ + struct mutex clients_lock;
u8 old_pm_cap; struct {
On Wed, Nov 25, 2020 at 01:37:06PM -0500, Lyude Paul wrote:
On Tue, 2020-11-03 at 14:49 -0500, Jeremy Cline wrote:
Rather than protecting the nouveau_drm clients list with the lock within the "client" nouveau_cli, add a dedicated lock to serialize access to the list. This is both clearer and necessary to avoid lockdep being upset with us when we need to iterate through all the clients in the list and potentially lock their mutex, which is the same class as the lock protecting the entire list.
Signed-off-by: Jeremy Cline jcline@redhat.com
drivers/gpu/drm/nouveau/nouveau_drm.c | 9 +++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 +++++ 2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index 4fe4d664c5f2..d182b877258a 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -557,6 +557,7 @@ nouveau_drm_device_init(struct drm_device *dev) nvkm_dbgopt(nouveau_debug, "DRM"); INIT_LIST_HEAD(&drm->clients); + mutex_init(&drm->clients_lock);
Looks like you forgot to hook up mutex_destroy() somewhere. Note there's actually plenty of code in nouveau right now that forgets to do this, but at some point we should probably fix that and avoid adding more spots where there's no mutex_destroy().
I'm guilty of having looked at the existing locking init code in nouveau and modeling this work accordingly. I'll send out a fix for this shortly and look at tidying up the rest of the locks in a separate series. Thanks!
spin_lock_init(&drm->tile.lock); /* workaround an odd issue on nvc1 by disabling the device's @@ -1089,9 +1090,9 @@ nouveau_drm_open(struct drm_device *dev, struct drm_file *fpriv) fpriv->driver_priv = cli; - mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_add(&cli->head, &drm->clients); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock); done: if (ret && cli) { @@ -1117,9 +1118,9 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) nouveau_abi16_fini(cli->abi16); mutex_unlock(&cli->mutex); - mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_del(&cli->head); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock); nouveau_cli_fini(cli); kfree(cli); diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h index 9d04d1b36434..550e5f335146 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drv.h +++ b/drivers/gpu/drm/nouveau/nouveau_drv.h @@ -141,6 +141,11 @@ struct nouveau_drm { struct list_head clients; + /** + * @clients_lock: Protects access to the @clients list of &struct nouveau_cli. + */ + struct mutex clients_lock;
u8 old_pm_cap; struct {
-- Sincerely, Lyude Paul (she/her) Software Engineer at Red Hat
Note: I deal with a lot of emails and have a lot of bugs on my plate. If you've asked me a question, are waiting for a review/merge on a patch, etc. and I haven't responded in a while, please feel free to send me another email to check on my status. I don't bite!
The postclose handler can run after the device has been removed (or the driver has been unbound) since userspace clients are free to hold the file open the file as long as they want. Because the device removal callback frees the entire nouveau_drm structure, any reference to it in the postclose handler will result in a use-after-free.
To reproduce this, one must simply open the device file, unbind the driver (or physically remove the device), and then close the device file. This was found and can be reproduced easily with the IGT core_hotunplug tests.
To avoid this, all clients are cleaned up in the device finialization rather than deferring it to the postclose handler, and the postclose handler is protected by a critical section which ensures the drm_dev_unplug() and the postclose handler won't race.
This is not an ideal fix, since as I understand the proposed plan for the kernel<->userspace interface for hotplug support, destroying the client before the file is closed will cause problems. However, I believe to properly fix this issue, the lifetime of the nouveau_drm structure needs to be extended to match the drm_device, and this proved to be a rather invasive change. Thus, I've broken this out so the fix can be easily backported.
Signed-off-by: Jeremy Cline jcline@redhat.com --- drivers/gpu/drm/nouveau/nouveau_drm.c | 30 +++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index d182b877258a..74fab777f4d0 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -628,6 +628,7 @@ nouveau_drm_device_init(struct drm_device *dev) static void nouveau_drm_device_fini(struct drm_device *dev) { + struct nouveau_cli *cli, *temp_cli; struct nouveau_drm *drm = nouveau_drm(dev);
if (nouveau_pmops_runtime()) { @@ -652,6 +653,24 @@ nouveau_drm_device_fini(struct drm_device *dev) nouveau_ttm_fini(drm); nouveau_vga_fini(drm);
+ /* + * There may be existing clients from as-yet unclosed files. For now, + * clean them up here rather than deferring until the file is closed, + * but this likely not correct if we want to support hot-unplugging + * properly. + */ + mutex_lock(&drm->clients_lock); + list_for_each_entry_safe(cli, temp_cli, &drm->clients, head) { + list_del(&cli->head); + mutex_lock(&cli->mutex); + if (cli->abi16) + nouveau_abi16_fini(cli->abi16); + mutex_unlock(&cli->mutex); + nouveau_cli_fini(cli); + kfree(cli); + } + mutex_unlock(&drm->clients_lock); + nouveau_cli_fini(&drm->client); nouveau_cli_fini(&drm->master); nvif_parent_dtor(&drm->parent); @@ -1110,6 +1129,16 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) { struct nouveau_cli *cli = nouveau_cli(fpriv); struct nouveau_drm *drm = nouveau_drm(dev); + int dev_index; + + /* + * The device is gone, and as it currently stands all clients are + * cleaned up in the removal codepath. In the future this may change + * so that we can support hot-unplugging, but for now we immediately + * return to avoid a double-free situation. + */ + if (!drm_dev_enter(dev, &dev_index)) + return;
pm_runtime_get_sync(dev->dev);
@@ -1126,6 +1155,7 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) kfree(cli); pm_runtime_mark_last_busy(dev->dev); pm_runtime_put_autosuspend(dev->dev); + drm_dev_exit(dev_index); }
static const struct drm_ioctl_desc
On Tue, 2020-11-03 at 14:49 -0500, Jeremy Cline wrote:
The postclose handler can run after the device has been removed (or the driver has been unbound) since userspace clients are free to hold the file open the file as long as they want. Because the device removal
^ typo
callback frees the entire nouveau_drm structure, any reference to it in the postclose handler will result in a use-after-free.
To reproduce this, one must simply open the device file, unbind the driver (or physically remove the device), and then close the device file. This was found and can be reproduced easily with the IGT core_hotunplug tests.
To avoid this, all clients are cleaned up in the device finialization rather than deferring it to the postclose handler, and the postclose handler is protected by a critical section which ensures the drm_dev_unplug() and the postclose handler won't race.
This is not an ideal fix, since as I understand the proposed plan for the kernel<->userspace interface for hotplug support, destroying the client before the file is closed will cause problems. However, I believe to properly fix this issue, the lifetime of the nouveau_drm structure needs to be extended to match the drm_device, and this proved to be a rather invasive change. Thus, I've broken this out so the fix can be easily backported.
JFYI - if the intent is for this to be backported, you should add:
Cc: stable@vger.kernel.org
Signed-off-by: Jeremy Cline jcline@redhat.com
drivers/gpu/drm/nouveau/nouveau_drm.c | 30 +++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index d182b877258a..74fab777f4d0 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -628,6 +628,7 @@ nouveau_drm_device_init(struct drm_device *dev) static void nouveau_drm_device_fini(struct drm_device *dev) { + struct nouveau_cli *cli, *temp_cli; struct nouveau_drm *drm = nouveau_drm(dev); if (nouveau_pmops_runtime()) { @@ -652,6 +653,24 @@ nouveau_drm_device_fini(struct drm_device *dev) nouveau_ttm_fini(drm); nouveau_vga_fini(drm); + /* + * There may be existing clients from as-yet unclosed files. For now, + * clean them up here rather than deferring until the file is closed, + * but this likely not correct if we want to support hot-unplugging + * properly. + */ + mutex_lock(&drm->clients_lock); + list_for_each_entry_safe(cli, temp_cli, &drm->clients, head) { + list_del(&cli->head); + mutex_lock(&cli->mutex); + if (cli->abi16) + nouveau_abi16_fini(cli->abi16); + mutex_unlock(&cli->mutex); + nouveau_cli_fini(cli); + kfree(cli); + } + mutex_unlock(&drm->clients_lock);
nouveau_cli_fini(&drm->client); nouveau_cli_fini(&drm->master); nvif_parent_dtor(&drm->parent); @@ -1110,6 +1129,16 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) { struct nouveau_cli *cli = nouveau_cli(fpriv); struct nouveau_drm *drm = nouveau_drm(dev); + int dev_index;
+ /* + * The device is gone, and as it currently stands all clients are + * cleaned up in the removal codepath. In the future this may change + * so that we can support hot-unplugging, but for now we immediately + * return to avoid a double-free situation. + */ + if (!drm_dev_enter(dev, &dev_index)) + return; pm_runtime_get_sync(dev->dev); @@ -1126,6 +1155,7 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) kfree(cli); pm_runtime_mark_last_busy(dev->dev); pm_runtime_put_autosuspend(dev->dev); + drm_dev_exit(dev_index); } static const struct drm_ioctl_desc
This series fixes a number of use-after-frees in nouveau's postclose() handler. It was discovered by pointing IGT's core_hotunplug tests at a nouveau device, but the steps to reproduce it are simple:
1. Open the device file 2. Unbind the driver or remove the device 3. Close the file opened in step 1.
During the device removal, the nouveau_drm structure is de-allocated, but is dereferenced in the postclose() handler.
One obvious solution is to ensure all the operations in the postclose() handler are valid by extending the lifetime of the nouveau_drm structure. This is possible with the new devm_drm_dev_alloc() interface, but the change is somewhat invasive so I thought it best to submit that work separately.
Instead, we make use of the drm_dev_unplug() API, clean up all clients in the device removal call, and check to make sure the device has not been unplugged in the postclose() handler. While this does not enable hot-unplug support for nouveau, it's enough to avoid crashing the kernel and leads to all the core_hotunplug tests to pass.
This series reroll addresses a missing mutex_destroy() call and a typo in a commit message.
Jeremy Cline (3): drm/nouveau: use drm_dev_unplug() during device removal drm/nouveau: Add a dedicated mutex for the clients list drm/nouveau: clean up all clients on device removal
drivers/gpu/drm/nouveau/nouveau_drm.c | 42 +++++++++++++++++++++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 ++++ 2 files changed, 42 insertions(+), 5 deletions(-)
Nouveau does not currently support hot-unplugging, but it still makes sense to switch from drm_dev_unregister() to drm_dev_unplug(). drm_dev_unplug() calls drm_dev_unregister() after marking the device as unplugged, but only after any device critical sections are finished.
Since nouveau isn't using drm_dev_enter() and drm_dev_exit(), there are no critical sections so this is nearly functionally equivalent. However, the DRM layer does check to see if the device is unplugged, and if it is returns appropriate error codes.
In the future nouveau can add critical sections in order to truly support hot-unplugging.
Cc: stable@vger.kernel.org Signed-off-by: Jeremy Cline jcline@redhat.com --- drivers/gpu/drm/nouveau/nouveau_drm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index d141a5f004af..4fe4d664c5f2 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -792,7 +792,7 @@ nouveau_drm_device_remove(struct drm_device *dev) struct nvkm_client *client; struct nvkm_device *device;
- drm_dev_unregister(dev); + drm_dev_unplug(dev);
dev->irq_enabled = false; client = nvxx_client(&drm->client.base);
Rather than protecting the nouveau_drm clients list with the lock within the "client" nouveau_cli, add a dedicated lock to serialize access to the list. This is both clearer and necessary to avoid lockdep being upset with us when we need to iterate through all the clients in the list and potentially lock their mutex, which is the same class as the lock protecting the entire list.
Cc: stable@vger.kernel.org Signed-off-by: Jeremy Cline jcline@redhat.com --- Changes since v1: - Add a mutex_destroy() call when destroying the device struct
drivers/gpu/drm/nouveau/nouveau_drm.c | 10 ++++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 +++++ 2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index 4fe4d664c5f2..6ee1adc9bd40 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -557,6 +557,7 @@ nouveau_drm_device_init(struct drm_device *dev) nvkm_dbgopt(nouveau_debug, "DRM");
INIT_LIST_HEAD(&drm->clients); + mutex_init(&drm->clients_lock); spin_lock_init(&drm->tile.lock);
/* workaround an odd issue on nvc1 by disabling the device's @@ -654,6 +655,7 @@ nouveau_drm_device_fini(struct drm_device *dev) nouveau_cli_fini(&drm->client); nouveau_cli_fini(&drm->master); nvif_parent_dtor(&drm->parent); + mutex_destroy(&drm->clients_lock); kfree(drm); }
@@ -1089,9 +1091,9 @@ nouveau_drm_open(struct drm_device *dev, struct drm_file *fpriv)
fpriv->driver_priv = cli;
- mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_add(&cli->head, &drm->clients); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock);
done: if (ret && cli) { @@ -1117,9 +1119,9 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) nouveau_abi16_fini(cli->abi16); mutex_unlock(&cli->mutex);
- mutex_lock(&drm->client.mutex); + mutex_lock(&drm->clients_lock); list_del(&cli->head); - mutex_unlock(&drm->client.mutex); + mutex_unlock(&drm->clients_lock);
nouveau_cli_fini(cli); kfree(cli); diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h index 9d04d1b36434..550e5f335146 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drv.h +++ b/drivers/gpu/drm/nouveau/nouveau_drv.h @@ -141,6 +141,11 @@ struct nouveau_drm {
struct list_head clients;
+ /** + * @clients_lock: Protects access to the @clients list of &struct nouveau_cli. + */ + struct mutex clients_lock; + u8 old_pm_cap;
struct {
The postclose handler can run after the device has been removed (or the driver has been unbound) since userspace clients are free to hold the file open as long as they want. Because the device removal callback frees the entire nouveau_drm structure, any reference to it in the postclose handler will result in a use-after-free.
To reproduce this, one must simply open the device file, unbind the driver (or physically remove the device), and then close the device file. This was found and can be reproduced easily with the IGT core_hotunplug tests.
To avoid this, all clients are cleaned up in the device finalization rather than deferring it to the postclose handler, and the postclose handler is protected by a critical section which ensures the drm_dev_unplug() and the postclose handler won't race.
This is not an ideal fix, since as I understand the proposed plan for the kernel<->userspace interface for hotplug support, destroying the client before the file is closed will cause problems. However, I believe to properly fix this issue, the lifetime of the nouveau_drm structure needs to be extended to match the drm_device, and this proved to be a rather invasive change. Thus, I've broken this out so the fix can be easily backported.
Cc: stable@vger.kernel.org Signed-off-by: Jeremy Cline jcline@redhat.com --- drivers/gpu/drm/nouveau/nouveau_drm.c | 30 +++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index 6ee1adc9bd40..afaf1774ee35 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -628,6 +628,7 @@ nouveau_drm_device_init(struct drm_device *dev) static void nouveau_drm_device_fini(struct drm_device *dev) { + struct nouveau_cli *cli, *temp_cli; struct nouveau_drm *drm = nouveau_drm(dev);
if (nouveau_pmops_runtime()) { @@ -652,6 +653,24 @@ nouveau_drm_device_fini(struct drm_device *dev) nouveau_ttm_fini(drm); nouveau_vga_fini(drm);
+ /* + * There may be existing clients from as-yet unclosed files. For now, + * clean them up here rather than deferring until the file is closed, + * but this likely not correct if we want to support hot-unplugging + * properly. + */ + mutex_lock(&drm->clients_lock); + list_for_each_entry_safe(cli, temp_cli, &drm->clients, head) { + list_del(&cli->head); + mutex_lock(&cli->mutex); + if (cli->abi16) + nouveau_abi16_fini(cli->abi16); + mutex_unlock(&cli->mutex); + nouveau_cli_fini(cli); + kfree(cli); + } + mutex_unlock(&drm->clients_lock); + nouveau_cli_fini(&drm->client); nouveau_cli_fini(&drm->master); nvif_parent_dtor(&drm->parent); @@ -1111,6 +1130,16 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) { struct nouveau_cli *cli = nouveau_cli(fpriv); struct nouveau_drm *drm = nouveau_drm(dev); + int dev_index; + + /* + * The device is gone, and as it currently stands all clients are + * cleaned up in the removal codepath. In the future this may change + * so that we can support hot-unplugging, but for now we immediately + * return to avoid a double-free situation. + */ + if (!drm_dev_enter(dev, &dev_index)) + return;
pm_runtime_get_sync(dev->dev);
@@ -1127,6 +1156,7 @@ nouveau_drm_postclose(struct drm_device *dev, struct drm_file *fpriv) kfree(cli); pm_runtime_mark_last_busy(dev->dev); pm_runtime_put_autosuspend(dev->dev); + drm_dev_exit(dev_index); }
static const struct drm_ioctl_desc
This patch series is:
Reviewed-by: Lyude Paul lyude@redhat.com
Btw - in the future if you need to send a respin of multiple patches, you need to send it as it's own separate series instead of replying to the previous one (one-off respins can just be posted as replies though), otherwise patchwork won't pick it up
On Wed, 2020-11-25 at 15:26 -0500, Jeremy Cline wrote:
This series fixes a number of use-after-frees in nouveau's postclose() handler. It was discovered by pointing IGT's core_hotunplug tests at a nouveau device, but the steps to reproduce it are simple:
- Open the device file
- Unbind the driver or remove the device
- Close the file opened in step 1.
During the device removal, the nouveau_drm structure is de-allocated, but is dereferenced in the postclose() handler.
One obvious solution is to ensure all the operations in the postclose() handler are valid by extending the lifetime of the nouveau_drm structure. This is possible with the new devm_drm_dev_alloc() interface, but the change is somewhat invasive so I thought it best to submit that work separately.
Instead, we make use of the drm_dev_unplug() API, clean up all clients in the device removal call, and check to make sure the device has not been unplugged in the postclose() handler. While this does not enable hot-unplug support for nouveau, it's enough to avoid crashing the kernel and leads to all the core_hotunplug tests to pass.
This series reroll addresses a missing mutex_destroy() call and a typo in a commit message.
Jeremy Cline (3): drm/nouveau: use drm_dev_unplug() during device removal drm/nouveau: Add a dedicated mutex for the clients list drm/nouveau: clean up all clients on device removal
drivers/gpu/drm/nouveau/nouveau_drm.c | 42 +++++++++++++++++++++++---- drivers/gpu/drm/nouveau/nouveau_drv.h | 5 ++++ 2 files changed, 42 insertions(+), 5 deletions(-)
Hi,
On Fri, Mar 26, 2021 at 06:00:51PM -0400, Lyude Paul wrote:
This patch series is:
Reviewed-by: Lyude Paul lyude@redhat.com
Btw - in the future if you need to send a respin of multiple patches, you need to send it as it's own separate series instead of replying to the previous one (one-off respins can just be posted as replies though), otherwise patchwork won't pick it up
Did this patch series somehow fall through the cracks or got lost?
Regards, Salvatore
It may have been, we're in the process of trying to change around how we currently accept nouveau patches to stop this from happening in the future.
Ben, whenever you get a moment can you take a look at this?
On Mon, 2021-08-16 at 09:03 +0200, Salvatore Bonaccorso wrote:
Hi,
On Fri, Mar 26, 2021 at 06:00:51PM -0400, Lyude Paul wrote:
This patch series is:
Reviewed-by: Lyude Paul lyude@redhat.com
Btw - in the future if you need to send a respin of multiple patches, you need to send it as it's own separate series instead of replying to the previous one (one-off respins can just be posted as replies though), otherwise patchwork won't pick it up
Did this patch series somehow fall through the cracks or got lost?
Regards, Salvatore
Hi Ben,
On Tue, Aug 17, 2021 at 04:32:31PM -0400, Lyude Paul wrote:
It may have been, we're in the process of trying to change around how we currently accept nouveau patches to stop this from happening in the future.
Ben, whenever you get a moment can you take a look at this?
On Mon, 2021-08-16 at 09:03 +0200, Salvatore Bonaccorso wrote:
Hi,
On Fri, Mar 26, 2021 at 06:00:51PM -0400, Lyude Paul wrote:
This patch series is:
Reviewed-by: Lyude Paul lyude@redhat.com
Btw - in the future if you need to send a respin of multiple patches, you need to send it as it's own separate series instead of replying to the previous one (one-off respins can just be posted as replies though), otherwise patchwork won't pick it up
Did this patch series somehow fall through the cracks or got lost?
Looking some older threads, noticed this one. Ben did you got a chance to look at it, or is it now irrelevant by other means?
Regards, Salvatore
I am currently checking the ML for such old patches, just have to make sure it's actually fine and not breaking stuff as well.
But I think we will pull this in soonish, I just also work on improving our CI stuff at the same time by trying out some things.
On Mon, Oct 11, 2021 at 9:06 AM Salvatore Bonaccorso carnil@debian.org wrote:
Hi Ben,
On Tue, Aug 17, 2021 at 04:32:31PM -0400, Lyude Paul wrote:
It may have been, we're in the process of trying to change around how we currently accept nouveau patches to stop this from happening in the future.
Ben, whenever you get a moment can you take a look at this?
On Mon, 2021-08-16 at 09:03 +0200, Salvatore Bonaccorso wrote:
Hi,
On Fri, Mar 26, 2021 at 06:00:51PM -0400, Lyude Paul wrote:
This patch series is:
Reviewed-by: Lyude Paul lyude@redhat.com
Btw - in the future if you need to send a respin of multiple patches, you need to send it as it's own separate series instead of replying to the previous one (one-off respins can just be posted as replies though), otherwise patchwork won't pick it up
Did this patch series somehow fall through the cracks or got lost?
Looking some older threads, noticed this one. Ben did you got a chance to look at it, or is it now irrelevant by other means?
Regards, Salvatore
dri-devel@lists.freedesktop.org
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Jeremy Cline -
Karol Herbst -
Lyude Paul -
Salvatore Bonaccorso