linux-hardening - [PATCH v2] drivers/bluetooth: Remove all strcpy() uses

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Date:   Sat, 24 Jul 2021 14:21:52 +0200
From:   Len Baker <len.baker@....com>
To:     Kees Cook <keescook@...omium.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     Len Baker <len.baker@....com>, Adam Sampson <ats@...og.org>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH v2] drivers/bluetooth: Remove all strcpy() uses

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. The safe replacement is strscpy() but in
this case it is better to use the scnprintf to simplify the arithmetic.

This is a previous step in the path to remove the strcpy() function
entirely from the kernel.

Signed-off-by: Len Baker <len.baker@....com>
---
Changelog v1 -> v2
- Add spaces to the "plus" sign.
- Use the correct size for the fw_dump_ptr buffer (Adam Sampson)

 drivers/bluetooth/btmrvl_sdio.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/drivers/bluetooth/btmrvl_sdio.c b/drivers/bluetooth/btmrvl_sdio.c
index cddd350beba3..68378b42ea7f 100644
--- a/drivers/bluetooth/btmrvl_sdio.c
+++ b/drivers/bluetooth/btmrvl_sdio.c
@@ -1350,6 +1350,7 @@ static void btmrvl_sdio_coredump(struct device *dev)
 	u8 *dbg_ptr, *end_ptr, *fw_dump_data, *fw_dump_ptr;
 	u8 dump_num = 0, idx, i, read_reg, doneflag = 0;
 	u32 memory_size, fw_dump_len = 0;
+	int size = 0;

 	card = sdio_get_drvdata(func);
 	priv = card->priv;
@@ -1478,7 +1479,7 @@ static void btmrvl_sdio_coredump(struct device *dev)
 	if (fw_dump_len == 0)
 		return;

-	fw_dump_data = vzalloc(fw_dump_len+1);
+	fw_dump_data = vzalloc(fw_dump_len + 1);
 	if (!fw_dump_data) {
 		BT_ERR("Vzalloc fw_dump_data fail!");
 		return;
@@ -1493,20 +1494,18 @@ static void btmrvl_sdio_coredump(struct device *dev)
 		struct memory_type_mapping *entry = &mem_type_mapping_tbl[idx];

 		if (entry->mem_ptr) {
-			strcpy(fw_dump_ptr, "========Start dump ");
-			fw_dump_ptr += strlen("========Start dump ");
-
-			strcpy(fw_dump_ptr, entry->mem_name);
-			fw_dump_ptr += strlen(entry->mem_name);
-
-			strcpy(fw_dump_ptr, "========\n");
-			fw_dump_ptr += strlen("========\n");
-
-			memcpy(fw_dump_ptr, entry->mem_ptr, entry->mem_size);
-			fw_dump_ptr += entry->mem_size;
-
-			strcpy(fw_dump_ptr, "\n========End dump========\n");
-			fw_dump_ptr += strlen("\n========End dump========\n");
+			size += scnprintf(fw_dump_ptr + size,
+					  fw_dump_len + 1 - size,
+					  "========Start dump %s========\n",
+					  entry->mem_name);
+
+			memcpy(fw_dump_ptr + size, entry->mem_ptr,
+			       entry->mem_size);
+			size += entry->mem_size;
+
+			size += scnprintf(fw_dump_ptr + size,
+					  fw_dump_len + 1 - size,
+					  "\n========End dump========\n");

 			vfree(mem_type_mapping_tbl[idx].mem_ptr);
 			mem_type_mapping_tbl[idx].mem_ptr = NULL;
--
2.25.1