linux-kernel - [PATCH 1/3] venus: core: handle race condititon for core ops

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Message-Id: <1596719855-1725-2-git-send-email-mansur@codeaurora.org>
Date:   Thu,  6 Aug 2020 18:47:33 +0530
From:   Mansur Alisha Shaik <mansur@...eaurora.org>
To:     linux-media@...r.kernel.org, stanimir.varbanov@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        vgarodia@...eaurora.org,
        Mansur Alisha Shaik <mansur@...eaurora.org>
Subject: [PATCH 1/3] venus: core: handle race condititon for core ops

For core ops we are having only write protect but
there is no read protect, because of this in mult
-threading and concurrency, one CPU core is readi
-ing without waiting which is causing the NULL
pointer dereferece crash.

one such scenario is as show below, where in one
core core->ops becoming NULL and in another core
calling core->ops->session_init().

CPU: 7(core):
Call trace:
 hfi_session_init+0x180/0x1dc [venus_core]
 vdec_queue_setup+0x9c/0x364 [venus_dec]
 vb2_core_reqbufs+0x1e4/0x368 [videobuf2_common]
 vb2_reqbufs+0x4c/0x64 [videobuf2_v4l2]
 v4l2_m2m_reqbufs+0x50/0x84 [v4l2_mem2mem]
 v4l2_m2m_ioctl_reqbufs+0x2c/0x38 [v4l2_mem2mem]
 v4l_reqbufs+0x4c/0x5c
__video_do_ioctl+0x2b0/0x39c

CPU: 0(core):
Call trace:
 venus_shutdown+0x98/0xfc [venus_core]
 venus_sys_error_handler+0x64/0x148 [venus_core]
 process_one_work+0x210/0x3d0
 worker_thread+0x248/0x3f4
 kthread+0x11c/0x12c

Signed-off-by: Mansur Alisha Shaik <mansur@...eaurora.org>
---
 drivers/media/platform/qcom/venus/core.c | 2 +-
 drivers/media/platform/qcom/venus/hfi.c  | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
index 203c653..fe99c83 100644
--- a/drivers/media/platform/qcom/venus/core.c
+++ b/drivers/media/platform/qcom/venus/core.c
@@ -64,8 +64,8 @@ static void venus_sys_error_handler(struct work_struct *work)
 	pm_runtime_get_sync(core->dev);
 
 	hfi_core_deinit(core, true);
-	hfi_destroy(core);
 	mutex_lock(&core->lock);
+	hfi_destroy(core);
 	venus_shutdown(core);
 
 	pm_runtime_put_sync(core->dev);
diff --git a/drivers/media/platform/qcom/venus/hfi.c b/drivers/media/platform/qcom/venus/hfi.c
index a211eb9..2eeb31f 100644
--- a/drivers/media/platform/qcom/venus/hfi.c
+++ b/drivers/media/platform/qcom/venus/hfi.c
@@ -195,7 +195,7 @@ EXPORT_SYMBOL_GPL(hfi_session_create);
 int hfi_session_init(struct venus_inst *inst, u32 pixfmt)
 {
 	struct venus_core *core = inst->core;
-	const struct hfi_ops *ops = core->ops;
+	const struct hfi_ops *ops;
 	int ret;
 
 	if (inst->state != INST_UNINIT)
@@ -204,10 +204,13 @@ int hfi_session_init(struct venus_inst *inst, u32 pixfmt)
 	inst->hfi_codec = to_codec_type(pixfmt);
 	reinit_completion(&inst->done);
 
+	mutex_lock(&core->lock);
+	ops = core->ops;
 	ret = ops->session_init(inst, inst->session_type, inst->hfi_codec);
 	if (ret)
 		return ret;
 
+	mutex_unlock(&core->lock);
 	ret = wait_session_msg(inst);
 	if (ret)
 		return ret;
-- 
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