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Tue, 15 Jul 2025 08:48:59 +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 IKNZF/sVdmgCWwAAD6G6ig (envelope-from ); Tue, 15 Jul 2025 08:48:59 +0000 From: Thomas Zimmermann To: thierry.reding@gmail.com, mperttunen@nvidia.com, airlied@gmail.com, simona@ffwll.ch, jonathanh@nvidia.com Cc: linux-tegra@vger.kernel.org, dri-devel@lists.freedesktop.org, Thomas Zimmermann Subject: [PATCH] Revert "drm/tegra: Use dma_buf from GEM object instance" Date: Tue, 15 Jul 2025 10:45:39 +0200 Message-ID: <20250715084549.41473-1-tzimmermann@suse.de> X-Mailer: git-send-email 2.50.0 Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-1.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; TAGGED_RCPT(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_TO(0.00)[gmail.com,nvidia.com,ffwll.ch]; RCPT_COUNT_SEVEN(0.00)[8]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:mid,imap1.dmz-prg2.suse.org:helo]; RCVD_COUNT_TWO(0.00)[2]; FREEMAIL_ENVRCPT(0.00)[gmail.com] X-Spam-Flag: NO X-Spam-Score: -1.30 This reverts commit 482c7e296edc0f594e8869a789a40be53c49bd6a. 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 --- drivers/gpu/drm/tegra/gem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c index 41a285ec889f..8ede07fb7a21 100644 --- a/drivers/gpu/drm/tegra/gem.c +++ b/drivers/gpu/drm/tegra/gem.c @@ -526,7 +526,7 @@ void tegra_bo_free_object(struct drm_gem_object *gem) if (drm_gem_is_imported(gem)) { dma_buf_unmap_attachment_unlocked(gem->import_attach, bo->sgt, DMA_TO_DEVICE); - dma_buf_detach(gem->dma_buf, gem->import_attach); + dma_buf_detach(gem->import_attach->dmabuf, gem->import_attach); } } -- 2.50.0