From: Thomas Zimmermann <tzimmermann@suse.de> stable inclusion from stable-v6.6.99 commit cb4c956a15f8b7f870649454771fc3761f504b5f category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ICOXN8 CVE: CVE-2025-38449 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 5307dce878d4126e1b375587318955bd019c3741 upstream. A GEM handle can be released while the GEM buffer object is attached to a DRM framebuffer. This leads to the release of the dma-buf backing the buffer object, if any. [1] Trying to use the framebuffer in further mode-setting operations leads to a segmentation fault. Most easily happens with driver that use shadow planes for vmap-ing the dma-buf during a page flip. An example is shown below. [ 156.791968] ------------[ cut here ]------------ [ 156.796830] WARNING: CPU: 2 PID: 2255 at drivers/dma-buf/dma-buf.c:1527 dma_buf_vmap+0x224/0x430 [...] [ 156.942028] RIP: 0010:dma_buf_vmap+0x224/0x430 [ 157.043420] Call Trace: [ 157.045898] <TASK> [ 157.048030] ? show_trace_log_lvl+0x1af/0x2c0 [ 157.052436] ? show_trace_log_lvl+0x1af/0x2c0 [ 157.056836] ? show_trace_log_lvl+0x1af/0x2c0 [ 157.061253] ? drm_gem_shmem_vmap+0x74/0x710 [ 157.065567] ? dma_buf_vmap+0x224/0x430 [ 157.069446] ? __warn.cold+0x58/0xe4 [ 157.073061] ? dma_buf_vmap+0x224/0x430 [ 157.077111] ? report_bug+0x1dd/0x390 [ 157.080842] ? handle_bug+0x5e/0xa0 [ 157.084389] ? exc_invalid_op+0x14/0x50 [ 157.088291] ? asm_exc_invalid_op+0x16/0x20 [ 157.092548] ? dma_buf_vmap+0x224/0x430 [ 157.096663] ? dma_resv_get_singleton+0x6d/0x230 [ 157.101341] ? __pfx_dma_buf_vmap+0x10/0x10 [ 157.105588] ? __pfx_dma_resv_get_singleton+0x10/0x10 [ 157.110697] drm_gem_shmem_vmap+0x74/0x710 [ 157.114866] drm_gem_vmap+0xa9/0x1b0 [ 157.118763] drm_gem_vmap_unlocked+0x46/0xa0 [ 157.123086] drm_gem_fb_vmap+0xab/0x300 [ 157.126979] drm_atomic_helper_prepare_planes.part.0+0x487/0xb10 [ 157.133032] ? lockdep_init_map_type+0x19d/0x880 [ 157.137701] drm_atomic_helper_commit+0x13d/0x2e0 [ 157.142671] ? drm_atomic_nonblocking_commit+0xa0/0x180 [ 157.147988] drm_mode_atomic_ioctl+0x766/0xe40 [...] [ 157.346424] ---[ end trace 0000000000000000 ]--- Acquiring GEM handles for the framebuffer's GEM buffer objects prevents this from happening. The framebuffer's cleanup later puts the handle references. Commit 1a148af06000 ("drm/gem-shmem: Use dma_buf from GEM object instance") triggers the segmentation fault easily by using the dma-buf field more widely. The underlying issue with reference counting has been present before. v2: - acquire the handle instead of the BO (Christian) - fix comment style (Christian) - drop the Fixes tag (Christian) - rename err_ gotos - add missing Link tag Suggested-by: Christian König <christian.koenig@amd.com> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Link: https://elixir.bootlin.com/linux/v6.15/source/drivers/gpu/drm/drm_gem.c#L241 # [1] Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Anusha Srivatsa <asrivats@redhat.com> Cc: Christian König <christian.koenig@amd.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: "Christian König" <christian.koenig@amd.com> Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Cc: <stable@vger.kernel.org> Reviewed-by: Christian König <christian.koenig@amd.com> Link: https://lore.kernel.org/r/20250630084001.293053-1-tzimmermann@suse.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [Backport] drm/framebuffer: Acquire internal references on GEM handles stable inclusion from stable-v6.6.99 commit 2e2e9b3d708473040a08ab884f7dc2369752bb69 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ICOXN8 CVE: CVE-2025-38449 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit f6bfc9afc7510cb5e6fbe0a17c507917b0120280 upstream. Acquire GEM handles in drm_framebuffer_init() and release them in the corresponding drm_framebuffer_cleanup(). Ties the handle's lifetime to the framebuffer. Not all GEM buffer objects have GEM handles. If not set, no refcounting takes place. This is the case for some fbdev emulation. This is not a problem as these GEM objects do not use dma-bufs and drivers will not release them while fbdev emulation is running. Framebuffer flags keep a bit per color plane of which the framebuffer holds a GEM handle reference. As all drivers use drm_framebuffer_init(), they will now all hold dma-buf references as fixed in commit 5307dce878d4 ("drm/gem: Acquire references on GEM handles for framebuffers"). In the GEM framebuffer helpers, restore the original ref counting on buffer objects. As the helpers for handle refcounting are now no longer called from outside the DRM core, unexport the symbols. v3: - don't mix internal flags with mode flags (Christian) v2: - track framebuffer handle refs by flag - drop gma500 cleanup (Christian) Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Fixes: 5307dce878d4 ("drm/gem: Acquire references on GEM handles for framebuffers") Reported-by: Bert Karwatzki <spasswolf@web.de> Closes: https://lore.kernel.org/dri-devel/20250703115915.3096-1-spasswolf@web.de/ Tested-by: Bert Karwatzki <spasswolf@web.de> Tested-by: Mario Limonciello <superm1@kernel.org> Tested-by: Borislav Petkov (AMD) <bp@alien8.de> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Anusha Srivatsa <asrivats@redhat.com> Cc: Christian König <christian.koenig@amd.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: "Christian König" <christian.koenig@amd.com> Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Cc: <stable@vger.kernel.org> Reviewed-by: Christian König <christian.koenig@amd.com> Link: https://lore.kernel.org/r/20250707131224.249496-1-tzimmermann@suse.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: drivers/gpu/drm/drm_gem.c drivers/gpu/drm/drm_internal.h drivers/gpu/drm/drm_gem_framebuffer_helper.c include/drm/drm_framebuffer.h drivers/gpu/drm/drm_framebuffer.c [Wupeng Ma: context conflicts; Since the fix patch revert some changes which lead to less conflicts if merge these two patches as a whole, merge these two; replace guard with mutex_lock since gurad is not introduced.] Signed-off-by: Wupeng Ma <mawupeng1@huawei.com> --- drivers/gpu/drm/drm_framebuffer.c | 31 +++++++++++++- drivers/gpu/drm/drm_gem.c | 67 ++++++++++++++++++++++++++----- drivers/gpu/drm/drm_internal.h | 2 + include/drm/drm_framebuffer.h | 7 ++++ 4 files changed, 96 insertions(+), 11 deletions(-) diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c index b64a6ffc0aed..3c08beee7c44 100644 --- a/drivers/gpu/drm/drm_framebuffer.c +++ b/drivers/gpu/drm/drm_framebuffer.c @@ -681,11 +681,23 @@ void drm_framebuffer_free(struct kref *kref) int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb, const struct drm_framebuffer_funcs *funcs) { + unsigned int i; int ret; + bool exists; if (WARN_ON_ONCE(fb->dev != dev || !fb->format)) return -EINVAL; + for (i = 0; i < fb->format->num_planes; i++) { + if (drm_WARN_ON_ONCE(dev, fb->internal_flags & DRM_FRAMEBUFFER_HAS_HANDLE_REF(i))) + fb->internal_flags &= ~DRM_FRAMEBUFFER_HAS_HANDLE_REF(i); + if (fb->obj[i]) { + exists = drm_gem_object_handle_get_if_exists_unlocked(fb->obj[i]); + if (exists) + fb->internal_flags |= DRM_FRAMEBUFFER_HAS_HANDLE_REF(i); + } + } + INIT_LIST_HEAD(&fb->filp_head); fb->funcs = funcs; @@ -694,7 +706,7 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb, ret = __drm_mode_object_add(dev, &fb->base, DRM_MODE_OBJECT_FB, false, drm_framebuffer_free); if (ret) - goto out; + goto err; mutex_lock(&dev->mode_config.fb_lock); dev->mode_config.num_fb++; @@ -702,7 +714,16 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb, mutex_unlock(&dev->mode_config.fb_lock); drm_mode_object_register(dev, &fb->base); -out: + + return 0; + +err: + for (i = 0; i < fb->format->num_planes; i++) { + if (fb->internal_flags & DRM_FRAMEBUFFER_HAS_HANDLE_REF(i)) { + drm_gem_object_handle_put_unlocked(fb->obj[i]); + fb->internal_flags &= ~DRM_FRAMEBUFFER_HAS_HANDLE_REF(i); + } + } return ret; } EXPORT_SYMBOL(drm_framebuffer_init); @@ -779,6 +800,12 @@ EXPORT_SYMBOL(drm_framebuffer_unregister_private); void drm_framebuffer_cleanup(struct drm_framebuffer *fb) { struct drm_device *dev = fb->dev; + unsigned int i; + + for (i = 0; i < fb->format->num_planes; i++) { + if (fb->internal_flags & DRM_FRAMEBUFFER_HAS_HANDLE_REF(i)) + drm_gem_object_handle_put_unlocked(fb->obj[i]); + } mutex_lock(&dev->mode_config.fb_lock); list_del(&fb->head); diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index bf90625df3c5..134c55e7fc66 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -189,6 +189,49 @@ drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct drm_file *filp) mutex_unlock(&filp->prime.lock); } +static void drm_gem_object_handle_get(struct drm_gem_object *obj) +{ + struct drm_device *dev = obj->dev; + + drm_WARN_ON(dev, !mutex_is_locked(&dev->object_name_lock)); + + if (obj->handle_count++ == 0) + drm_gem_object_get(obj); +} + +/** + * drm_gem_object_handle_get_if_exists_unlocked - acquire reference on user-space handle, if any + * @obj: GEM object + * + * Acquires a reference on the GEM buffer object's handle. Required to keep + * the GEM object alive. Call drm_gem_object_handle_put_if_exists_unlocked() + * to release the reference. Does nothing if the buffer object has no handle. + * + * Returns: + * True if a handle exists, or false otherwise + */ +bool drm_gem_object_handle_get_if_exists_unlocked(struct drm_gem_object *obj) +{ + struct drm_device *dev = obj->dev; + + mutex_lock(&dev->object_name_lock); + + /* + * First ref taken during GEM object creation, if any. Some + * drivers set up internal framebuffers with GEM objects that + * do not have a GEM handle. Hence, this counter can be zero. + */ + if (!obj->handle_count) { + mutex_unlock(&dev->object_name_lock); + return false; + } + + drm_gem_object_handle_get(obj); + mutex_unlock(&dev->object_name_lock); + + return true; +} + /** * drm_gem_object_handle_free - release resources bound to userspace handles * @obj: GEM object to clean up. @@ -219,20 +262,26 @@ static void drm_gem_object_exported_dma_buf_free(struct drm_gem_object *obj) } } -static void -drm_gem_object_handle_put_unlocked(struct drm_gem_object *obj) +/** + * drm_gem_object_handle_put_unlocked - releases reference on user-space handle + * @obj: GEM object + * + * Releases a reference on the GEM buffer object's handle. Possibly releases + * the GEM buffer object and associated dma-buf objects. + */ +void drm_gem_object_handle_put_unlocked(struct drm_gem_object *obj) { struct drm_device *dev = obj->dev; bool final = false; - if (WARN_ON(obj->handle_count == 0)) + if (drm_WARN_ON(dev, READ_ONCE(obj->handle_count) == 0)) return; /* - * Must bump handle count first as this may be the last - * ref, in which case the object would disappear before we - * checked for a name - */ + * Must bump handle count first as this may be the last + * ref, in which case the object would disappear before we + * checked for a name + */ mutex_lock(&dev->object_name_lock); if (--obj->handle_count == 0) { @@ -385,8 +434,8 @@ drm_gem_handle_create_tail(struct drm_file *file_priv, int ret; WARN_ON(!mutex_is_locked(&dev->object_name_lock)); - if (obj->handle_count++ == 0) - drm_gem_object_get(obj); + + drm_gem_object_handle_get(obj); /* * Get the user-visible handle using idr. Preload and perform diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h index 8750f3f02b3f..2275c3caedb1 100644 --- a/drivers/gpu/drm/drm_internal.h +++ b/drivers/gpu/drm/drm_internal.h @@ -104,6 +104,8 @@ void drm_sysfs_lease_event(struct drm_device *dev); /* drm_gem.c */ int drm_gem_init(struct drm_device *dev); void drm_gem_destroy(struct drm_device *dev); +bool drm_gem_object_handle_get_if_exists_unlocked(struct drm_gem_object *obj); +void drm_gem_object_handle_put_unlocked(struct drm_gem_object *obj); int drm_gem_handle_create_tail(struct drm_file *file_priv, struct drm_gem_object *obj, u32 *handlep); diff --git a/include/drm/drm_framebuffer.h b/include/drm/drm_framebuffer.h index c50502c656e5..490070da98b0 100644 --- a/include/drm/drm_framebuffer.h +++ b/include/drm/drm_framebuffer.h @@ -23,6 +23,7 @@ #ifndef __DRM_FRAMEBUFFER_H__ #define __DRM_FRAMEBUFFER_H__ +#include <linux/bits.h> #include <linux/list.h> #include <linux/ctype.h> #include <drm/drm_mode_object.h> @@ -92,6 +93,8 @@ struct drm_framebuffer_funcs { unsigned num_clips); }; +#define DRM_FRAMEBUFFER_HAS_HANDLE_REF(_i) BIT(0u + (_i)) + /** * struct drm_framebuffer - frame buffer object * @@ -180,6 +183,10 @@ struct drm_framebuffer { * DRM_MODE_FB_MODIFIERS. */ int flags; + /** + * @internal_flags: Framebuffer flags like DRM_FRAMEBUFFER_HAS_HANDLE_REF. + */ + unsigned int internal_flags; /** * @hot_x: X coordinate of the cursor hotspot. Used by the legacy cursor * IOCTL when the driver supports cursor through a DRM_PLANE_TYPE_CURSOR -- 2.43.0