msm: vidc: Protect debug_buffer access in core_info_read with lock.

Serialize core_info_read with lock so that multiple concurrent
threads do not cause the write to overflow. Also have the bound
check to avoid overflow in write_str function.

CRs-Fixed: 2013361
Change-Id: Ia18a4b94cafd69af1d367861f2499fc202f18e9f
Signed-off-by: Abdulla Anam <abdullahanam@codeaurora.org>
Signed-off-by: Sanjay Singh <sisanj@codeaurora.org>

drivers/media/platform/msm/vidc/msm_v4l2_vidc.c

@@ -1,4 +1,4 @@
-/* Copyright (c) 2012-2016, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2012-2017, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -734,6 +734,8 @@ static int __init msm_vidc_init(void)
 	if (rc) {
 		dprintk(VIDC_ERR,
 			"Failed to register platform driver\n");
+		msm_vidc_debugfs_deinit_drv();
+		debugfs_remove_recursive(vidc_driver->debugfs_root);
 		kfree(vidc_driver);
 		vidc_driver = NULL;
 	}
@@ -744,6 +746,7 @@ static int __init msm_vidc_init(void)
 static void __exit msm_vidc_exit(void)
 {
 	platform_driver_unregister(&msm_vidc_driver);
+	msm_vidc_debugfs_deinit_drv();
 	debugfs_remove_recursive(vidc_driver->debugfs_root);
 	kfree(vidc_driver);
 	vidc_driver = NULL;

drivers/media/platform/msm/vidc/msm_vidc_debug.c

@@ -1,4 +1,4 @@
-/* Copyright (c) 2012-2016, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2012-2017, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -31,6 +31,7 @@ u32 msm_vidc_firmware_unload_delay = 15000;
 int msm_vidc_thermal_mitigation_disabled = 0x0;
 
 struct debug_buffer {
+	struct mutex lock;
 	char ptr[MAX_DBG_BUF_SIZE];
 	char *curr;
 	u32 filled_size;
@@ -57,8 +58,12 @@ static u32 write_str(struct debug_buffer *buffer, const char *fmt, ...)
 {
 	va_list args;
 	u32 size;
+
+	char *curr = buffer->curr;
+	char *end = buffer->ptr + MAX_DBG_BUF_SIZE;
+
 	va_start(args, fmt);
-	size = vscnprintf(buffer->curr, MAX_DBG_BUF_SIZE - 1, fmt, args);
+	size = vscnprintf(curr, end - curr, fmt, args);
 	va_end(args);
 	buffer->curr += size;
 	buffer->filled_size += size;
@@ -72,12 +77,15 @@ static ssize_t core_info_read(struct file *file, char __user *buf,
 	struct hfi_device *hdev;
 	struct hal_fw_info fw_info;
 	int i = 0, rc = 0;
+	ssize_t len = 0;
 
 	if (!core || !core->device) {
 		dprintk(VIDC_ERR, "Invalid params, core: %pK\n", core);
 		return 0;
 	}
 	hdev = core->device;
+
+	mutex_lock(&dbg_buf.lock);
 	INIT_DBG_BUF(dbg_buf);
 	write_str(&dbg_buf, "===============================\n");
 	write_str(&dbg_buf, "CORE %d: 0x%pK\n", core->id, core);
@@ -101,8 +109,11 @@ static ssize_t core_info_read(struct file *file, char __user *buf,
 			completion_done(&core->completions[SYS_MSG_INDEX(i)]) ?
 			"pending" : "done");
 	}
-	return simple_read_from_buffer(buf, count, ppos,
+	len = simple_read_from_buffer(buf, count, ppos,
 			dbg_buf.ptr, dbg_buf.filled_size);
+
+	mutex_unlock(&dbg_buf.lock);
+	return len;
 }
 
 static const struct file_operations core_info_fops = {
@@ -139,7 +150,10 @@ static const struct file_operations ssr_fops = {
 
 struct dentry *msm_vidc_debugfs_init_drv(void)
 {
-	struct dentry *dir = debugfs_create_dir("msm_vidc", NULL);
+	struct dentry *dir = NULL;
+
+	mutex_init(&dbg_buf.lock);
+	dir = debugfs_create_dir("msm_vidc", NULL);
 	if (IS_ERR_OR_NULL(dir)) {
 		dir = NULL;
 		goto failed_create_dir;
@@ -238,6 +252,7 @@ struct dentry *msm_vidc_debugfs_init_core(struct msm_vidc_core *core,
 		dprintk(VIDC_ERR, "Failed to create debugfs for msm_vidc\n");
 		goto failed_create_dir;
 	}
+
 	if (!debugfs_create_file("info", S_IRUGO, dir, core, &core_info_fops)) {
 		dprintk(VIDC_ERR, "debugfs_create_file: fail\n");
 		goto failed_create_dir;
@@ -291,10 +306,14 @@ static ssize_t inst_info_read(struct file *file, char __user *buf,
 {
 	struct msm_vidc_inst *inst = file->private_data;
 	int i, j;
+	ssize_t len = 0;
+
 	if (!inst) {
 		dprintk(VIDC_ERR, "Invalid params, core: %pK\n", inst);
 		return 0;
 	}
+
+	mutex_lock(&dbg_buf.lock);
 	INIT_DBG_BUF(dbg_buf);
 	write_str(&dbg_buf, "===============================\n");
 	write_str(&dbg_buf, "INSTANCE: 0x%pK (%s)\n", inst,
@@ -351,9 +370,10 @@ static ssize_t inst_info_read(struct file *file, char __user *buf,
 	write_str(&dbg_buf, "FBD Count: %d\n", inst->count.fbd);
 
 	publish_unreleased_reference(inst);
-
-	return simple_read_from_buffer(buf, count, ppos,
+	len = simple_read_from_buffer(buf, count, ppos,
 		dbg_buf.ptr, dbg_buf.filled_size);
+	mutex_unlock(&dbg_buf.lock);
+	return len;
 }
 
 static const struct file_operations inst_info_fops = {
@@ -434,3 +454,8 @@ void msm_vidc_debugfs_update(struct msm_vidc_inst *inst,
 	}
 }
 
+void msm_vidc_debugfs_deinit_drv(void)
+{
+	mutex_destroy(&dbg_buf.lock);
+}
+

drivers/media/platform/msm/vidc/msm_vidc_debug.h

@@ -1,4 +1,4 @@
-/* Copyright (c) 2012-2014, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2012-2014, 2017 The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -123,6 +123,7 @@ struct dentry *msm_vidc_debugfs_init_inst(struct msm_vidc_inst *inst,
 		struct dentry *parent);
 void msm_vidc_debugfs_update(struct msm_vidc_inst *inst,
 		enum msm_vidc_debugfs_event e);
+void msm_vidc_debugfs_deinit_drv(void);
 
 static inline void tic(struct msm_vidc_inst *i, enum profiling_points p,
 				 char *b)