[PATCH v2] dmaengine: xilinx: dpdma: Reserve space for a string terminator

[Jiale Yao <yaojiale02@163.com>]

xilinx_dpdma_debugfs_write() copies size bytes from userspace and parses
them with strsep() and strcasecmp(). If the input has no NUL within that
range, the parser can read beyond the allocation.

Use memdup_user_nul() to copy the complete input and append a terminating
NUL.

Fixes: 1d220435cab3 ("dmaengine: xilinx: dpdma: Add debugfs support")
Signed-off-by: Jiale Yao <yaojiale02@163.com>

---

Changes in v2:
- Replace kzalloc() and strncpy_from_user() with memdup_user_nul(), as
  suggested by Laurent.

diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
index d9a3542c4531..219d25be6c3a 100644
--- a/drivers/dma/xilinx/xilinx_dpdma.c
+++ b/drivers/dma/xilinx/xilinx_dpdma.c
@@ -410,15 +410,11 @@ static ssize_t xilinx_dpdma_debugfs_write(struct file *f,
 	if (dpdma_debugfs.testcase != DPDMA_TC_NONE)
 		return -EBUSY;
 
-	kern_buff = kzalloc(size, GFP_KERNEL);
-	if (!kern_buff)
-		return -ENOMEM;
+	kern_buff = memdup_user_nul(buf, size);
+	if (IS_ERR(kern_buff))
+		return PTR_ERR(kern_buff);
 	kern_buff_start = kern_buff;
 
-	ret = strncpy_from_user(kern_buff, buf, size);
-	if (ret < 0)
-		goto done;
-
 	/* Read the testcase name from a user request. */
 	testcase = strsep(&kern_buff, " ");
 
-- 
2.34.1