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RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Flag: NO Hi Am 25.08.26 um 10:44 schrieb shechenglong: > When drm_sysfs_minor_alloc() fails (e.g., due to -ENOMEM), the > following Oops occurs because an ERR_PTR is passed to put_device(): > > BUG: kernel NULL pointer dereference, address: 0000000000000030 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > RIP: 0010:kobject_put+0xd/0x60 > Call Trace: > drm_minor_alloc_release+0x1c/0x50 [drm] > drm_managed_release+0x96/0x160 [drm] > drm_dev_init+0x269/0x330 [drm] > drm_dev_alloc+0x3f/0x80 [drm] > virtio_gpu_probe+0x40/0x180 [virtio_gpu] > virtio_dev_probe+0x1fd/0x360 > ... > do_syscall_64+0xaf/0x500 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > > The call path that leads to this crash is: > > virtio_gpu_probe() > drm_dev_alloc() > drm_dev_init() > drm_minor_alloc() // allocates minor > drm_sysfs_minor_alloc() // returns ERR_PTR(-ENOMEM) > minor->kdev = ERR_PTR(-ENOMEM) // stored directly > return -ENOMEM > // drm_dev_init() fails, triggers cleanup: > drm_managed_release() > drm_minor_alloc_release(dev, minor) > put_device(minor->kdev) // ERR_PTR(-ENOMEM) dereferenced > kobject_put() // crashes at address 0x30 > > drm_minor_alloc() assigns the return value of drm_sysfs_minor_alloc() > directly to minor->kdev, even when it is an error pointer. The > subsequent cleanup unconditionally calls put_device(minor->kdev), > which dereferences the error pointer and causes a NULL-pointer > dereference (offset 0x30 into a non-page-mapped area). > > Fix this by using a temporary variable to hold the result of > drm_sysfs_minor_alloc(). If the allocation fails, we return the error > immediately, leaving minor->kdev as NULL (the whole minor structure is > zero-allocated). put_device(NULL) is explicitly allowed and safe. > > Fixes: f96306f9892b ("drm: manage drm_minor cleanup with drmm_") > > Signed-off-by: shechenglong Reviewed-by: Thomas Zimmermann Thanks for the fix. Best regards Thomas > --- > drivers/gpu/drm/drm_drv.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c > index 675675480..2348fbb21 100644 > --- a/drivers/gpu/drm/drm_drv.c > +++ b/drivers/gpu/drm/drm_drv.c > @@ -143,6 +143,7 @@ static void drm_minor_alloc_release(struct drm_device *dev, void *data) > static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type) > { > struct drm_minor *minor; > + struct device *kdev; > int r; > > minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL); > @@ -164,9 +165,11 @@ static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type) > if (r) > return r; > > - minor->kdev = drm_sysfs_minor_alloc(minor); > - if (IS_ERR(minor->kdev)) > - return PTR_ERR(minor->kdev); > + kdev = drm_sysfs_minor_alloc(minor); > + if (IS_ERR(kdev)) > + return PTR_ERR(kdev); > + > + minor->kdev = kdev; > > *drm_minor_get_slot(dev, type) = minor; > return 0; -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)