param: simple locking for sysfs-writable charp parameters

Since the writing to sysfs can free the old one, we need to block that
when we access the charp variables.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Dan Williams <dcbw@redhat.com>
Cc: John W. Linville <linville@tuxdriver.com>
Cc: Jing Huang <huangj@brocade.com>
Cc: James E.J. Bottomley <James.Bottomley@suse.de>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: libertas-dev@lists.infradead.org
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: linux-usb@vger.kernel.org

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/net/wireless/libertas_tf/if_usb.c b/drivers/net/wireless/libertas_tf/if_usb.c
index b172f5d87a3..41a4f214ade 100644
--- a/drivers/net/wireless/libertas_tf/if_usb.c
+++ b/drivers/net/wireless/libertas_tf/if_usb.c
@@ -811,12 +811,15 @@ static int if_usb_prog_firmware(struct if_usb_card *cardp)
 
         lbtf_deb_enter(LBTF_DEB_USB);
 
+        kparam_block_sysfs_write(fw_name);
         ret = request_firmware(&cardp->fw, lbtf_fw_name, &cardp->udev->dev);
         if (ret < 0) {
                 pr_err("request_firmware() failed with %#x\n", ret);
                 pr_err("firmware %s not found\n", lbtf_fw_name);
+                kparam_unblock_sysfs_write(fw_name);
                 goto done;
         }
+        kparam_unblock_sysfs_write(fw_name);
 
         if (check_fwfile_format(cardp->fw->data, cardp->fw->size))
                 goto release_fw;