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Mon, 25 May 2026 02:52:56 -0700 (PDT) From: Anand Moon To: Neil Armstrong , Mauro Carvalho Chehab , Greg Kroah-Hartman , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Maxime Jourdan , Hans Verkuil , linux-media@vger.kernel.org (open list:MESON VIDEO DECODER DRIVER FOR AMLOGIC SOCS), linux-amlogic@lists.infradead.org (open list:MESON VIDEO DECODER DRIVER FOR AMLOGIC SOCS), linux-staging@lists.linux.dev (open list:STAGING SUBSYSTEM), linux-arm-kernel@lists.infradead.org (moderated list:ARM/Amlogic Meson SoC support), linux-kernel@vger.kernel.org (open list) Cc: Anand Moon , Nicolas Dufresne , Sashiko Subject: [PATCH v5 3/6] media: meson: vdec: Set cur_sess before hardware vdec_poweron() Date: Mon, 25 May 2026 15:21:51 +0530 Message-ID: <20260525095216.12078-4-linux.amoon@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260525095216.12078-1-linux.amoon@gmail.com> References: <20260525095216.12078-1-linux.amoon@gmail.com> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vdec_poweron() initializes hardware and unmasks device interrupts. If an interrupt fires before core->cur_sess is set, vdec_isr() dereferences a NULL pointer when updating sess->last_irq_jiffies, leading to a kernel panic. Fix this by assigning core->cur_sess and updating sess->status under core->lock before calling vdec_poweron(). This ensures the interrupt handler always sees a valid session pointer. On the error path, clear core->cur_sess and reset sess->status to STATUS_STOPPED to avoid stale references. Following change also strengthens the hardware exclusivity check by holding core->lock during session assignment, preventing concurrent sessions from racing through cur_sess == NULL and corrupting hardware state. Cc: Nicolas Dufresne Reported-by: Sashiko Closes: https://lore.kernel.org/all/20260521090944.F35401F00A3D@smtp.kernel.org/ Fixes: 3e7f51bd9607 ("media: meson: add v4l2 m2m video decoder driver") Signed-off-by: Anand Moon --- v5: [Critical] Race condition between hardware power-on and `core->cur_sess` initialization leads to a NULL pointer dereference in the IRQ handler. --- drivers/staging/media/meson/vdec/vdec.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c index e72f54af026e..52ace4de967c 100644 --- a/drivers/staging/media/meson/vdec/vdec.c +++ b/drivers/staging/media/meson/vdec/vdec.c @@ -334,6 +334,11 @@ static int vdec_start_streaming(struct vb2_queue *q, unsigned int count) atomic_set(&sess->esparser_queued_bufs, 0); v4l2_ctrl_s_ctrl(sess->ctrl_min_buf_capture, 1); + mutex_lock(&core->lock); + core->cur_sess = sess; + sess->status = STATUS_INIT; + mutex_unlock(&core->lock); + ret = vdec_poweron(sess); if (ret) goto vififo_free; @@ -344,12 +349,14 @@ static int vdec_start_streaming(struct vb2_queue *q, unsigned int count) sess->recycle_thread = kthread_run(vdec_recycle_thread, sess, "vdec_recycle"); - sess->status = STATUS_INIT; - core->cur_sess = sess; schedule_work(&sess->esparser_queue_work); return 0; vififo_free: + mutex_lock(&core->lock); + core->cur_sess = NULL; + sess->status = STATUS_STOPPED; + mutex_unlock(&core->lock); dma_free_coherent(sess->core->dev, sess->vififo_size, sess->vififo_vaddr, sess->vififo_paddr); bufs_done: -- 2.50.1