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Tue, 15 Jul 2025 08:14:34 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id gBTjBeoNdmgJUAAAD6G6ig (envelope-from ); Tue, 15 Jul 2025 08:14:34 +0000 From: Thomas Zimmermann To: simona@ffwll.ch, airlied@gmail.com, christian.koenig@amd.com, torvalds@linux-foundation.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, l.stach@pengutronix.de, linux+etnaviv@armlinux.org.uk, kraxel@redhat.com, christian.gmeiner@gmail.com, dmitry.osipenko@collabora.com, gurchetansingh@chromium.org, olvaffe@gmail.com, zack.rusin@broadcom.com Cc: bcm-kernel-feedback-list@broadcom.com, dri-devel@lists.freedesktop.org, etnaviv@lists.freedesktop.org, virtualization@lists.linux.dev, intel-gfx@lists.freedesktop.org, Thomas Zimmermann , Simona Vetter Subject: [PATCH v2 6/7] Revert "drm/gem-shmem: Use dma_buf from GEM object instance" Date: Tue, 15 Jul 2025 10:07:57 +0200 Message-ID: <20250715081121.34473-7-tzimmermann@suse.de> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250715081121.34473-1-tzimmermann@suse.de> References: <20250715081121.34473-1-tzimmermann@suse.de> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-5.30 / 50.00]; REPLY(-4.00)[]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCPT_COUNT_TWELVE(0.00)[21]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; TAGGED_RCPT(0.00)[etnaviv]; FREEMAIL_TO(0.00)[ffwll.ch,gmail.com,amd.com,linux-foundation.org,linux.intel.com,kernel.org,pengutronix.de,armlinux.org.uk,redhat.com,collabora.com,chromium.org,broadcom.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:mid,suse.de:email]; RCVD_COUNT_TWO(0.00)[2]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; R_RATELIMIT(0.00)[to_ip_from(RLk1j8fm6pferx3phn9ndszqb3)]; FROM_EQ_ENVFROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com] X-Spam-Flag: NO X-Spam-Level: X-Spam-Score: -5.30 This reverts commit 1a148af06000e545e714fe3210af3d77ff903c11. The dma_buf field in struct drm_gem_object is not stable over the object instance's lifetime. The field becomes NULL when user space releases the final GEM handle on the buffer object. This resulted in a NULL-pointer deref. Workarounds in commit 5307dce878d4 ("drm/gem: Acquire references on GEM handles for framebuffers") and commit f6bfc9afc751 ("drm/framebuffer: Acquire internal references on GEM handles") only solved the problem partially. They especially don't work for buffer objects without a DRM framebuffer associated. Hence, this revert to going back to using .import_attach->dmabuf. Signed-off-by: Thomas Zimmermann Reviewed-by: Simona Vetter --- drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 8ac0b1fa5287..5d1349c34afd 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -351,7 +351,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, dma_resv_assert_held(obj->resv); if (drm_gem_is_imported(obj)) { - ret = dma_buf_vmap(obj->dma_buf, map); + ret = dma_buf_vmap(obj->import_attach->dmabuf, map); } else { pgprot_t prot = PAGE_KERNEL; @@ -413,7 +413,7 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, dma_resv_assert_held(obj->resv); if (drm_gem_is_imported(obj)) { - dma_buf_vunmap(obj->dma_buf, map); + dma_buf_vunmap(obj->import_attach->dmabuf, map); } else { dma_resv_assert_held(shmem->base.resv); -- 2.50.0