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Mon, 25 May 2026 02:52:47 -0700 (PDT) From: Anand Moon To: Neil Armstrong , Mauro Carvalho Chehab , Greg Kroah-Hartman , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Hans Verkuil , Maxime Jourdan , 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 2/6] media: meson: vdec: Protect session exclusivity check with lock Date: Mon, 25 May 2026 15:21:50 +0530 Message-ID: <20260525095216.12078-3-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 Add the check for an active hardware session is performed without holding the core->lock mutex. In multi-threaded environments, two concurrent STREAMON ioctls on different file descriptors can simultaneously find core->cur_sess to be NULL, bypass the check, and concurrently call vdec_poweron(), corrupting hardware state. Fix this by wrapping the session exclusivity check inside core->lock. 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: New patch. [High] Concurrent sessions can bypass the hardware exclusivity check, leading to simultaneous hardware programming. --- drivers/staging/media/meson/vdec/vdec.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c index 18a22b79e835..e72f54af026e 100644 --- a/drivers/staging/media/meson/vdec/vdec.c +++ b/drivers/staging/media/meson/vdec/vdec.c @@ -286,10 +286,13 @@ static int vdec_start_streaming(struct vb2_queue *q, unsigned int count) struct vb2_v4l2_buffer *buf; int ret; + mutex_lock(&core->lock); if (core->cur_sess && core->cur_sess != sess) { + mutex_unlock(&core->lock); ret = -EBUSY; goto bufs_done; } + mutex_unlock(&core->lock); if (q->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE) sess->streamon_out = 1; -- 2.50.1