[PATCH] Protect firmware loading with a mutex

Otherwise, two devices could try to load and parse the same firmware at
the same time.

Signed-off-by: Pavel Roskin <proski@gnu.org>

1 files changed, 18 insertions, 5 deletions

diff --git a/at76_usb.c b/at76_usb.c
index 2a3a784..0ec97e1 100644
--- a/at76_usb.c
+++ b/at76_usb.c
@@ -46,6 +46,9 @@
 
 static int at76_debug = DBG_DEFAULTS;
 
+/* Protect against concurrent firmware loading and parsing */
+static struct mutex fw_mutex;
+
 static struct fwentry firmwares[] = {
 	[0] = {""},
 	[BOARDTYPE_503_INTERSIL_3861] = {"atmel_at76c503-i3861.bin"},
@@ -5853,9 +5856,11 @@ static struct fwentry *at76_load_firmware(struct usb_device *udev,
 	struct at76_fw_header *fwh;
 	struct fwentry *fwe = &firmwares[board_type];
 
+	mutex_lock(&fw_mutex);
+
 	if (fwe->loaded) {
 		at76_dbg(DBG_FW, "re-using previously loaded fw");
-		return fwe;
+		goto fw_out;
 	}
 
 	at76_dbg(DBG_FW, "downloading firmware %s", fwe->fwname);
@@ -5864,7 +5869,7 @@ static struct fwentry *at76_load_firmware(struct usb_device *udev,
 		err("firmware %s not found.", fwe->fwname);
 		err("You may need to download the firmware from "
 		    "http://developer.berlios.de/projects/at76c503a/");
-		return NULL;
+		goto fw_out;
 	}
 
 	at76_dbg(DBG_FW, "got it.");
@@ -5872,7 +5877,7 @@ static struct fwentry *at76_load_firmware(struct usb_device *udev,
 
 	if (fwe->fw->size <= sizeof(*fwh)) {
 		err("firmware is too short (0x%zx)", fwe->fw->size);
-		return NULL;
+		goto fw_out;
 	}
 
 	/* CRC currently not checked */
@@ -5880,7 +5885,7 @@ static struct fwentry *at76_load_firmware(struct usb_device *udev,
 	if (fwe->board_type != board_type) {
 		err("board type mismatch, requested %u, got %u", board_type,
 		    fwe->board_type);
-		return NULL;
+		goto fw_out;
 	}
 
 	fwe->fw_version.major = fwh->major;
@@ -5903,7 +5908,13 @@ static struct fwentry *at76_load_firmware(struct usb_device *udev,
 		 le32_to_cpu(fwh->ext_fw_offset), le32_to_cpu(fwh->ext_fw_len));
 	at76_dbg(DBG_DEVSTART, "firmware id %s", str);
 
-	return fwe;
+      fw_out:
+	mutex_unlock(&fw_mutex);
+
+	if (fwe->loaded)
+		return fwe;
+	else
+		return NULL;
 }
 
 static int at76_probe(struct usb_interface *interface,
@@ -6035,6 +6046,8 @@ static int __init at76_mod_init(void)
 
 	printk(KERN_INFO DRIVER_DESC " " DRIVER_VERSION " loading\n");
 
+	mutex_init(&fw_mutex);
+
 	/* register this driver with the USB subsystem */
 	result = usb_register(&at76_driver);
 	if (result < 0) {