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, 10 insertions, 0 deletions

diff --git a/arch/um/drivers/hostaudio_kern.c b/arch/um/drivers/hostaudio_kern.c
index 68142df76608..0c46e398cd8f 100644
--- a/arch/um/drivers/hostaudio_kern.c
+++ b/arch/um/drivers/hostaudio_kern.c
@@ -187,7 +187,9 @@ static int hostaudio_open(struct inode *inode, struct file *file)
         int ret;
 
 #ifdef DEBUG
+        kparam_block_sysfs_write(dsp);
         printk(KERN_DEBUG "hostaudio: open called (host: %s)\n", dsp);
+        kparam_unblock_sysfs_write(dsp);
 #endif
 
         state = kmalloc(sizeof(struct hostaudio_state), GFP_KERNEL);
@@ -199,9 +201,11 @@ static int hostaudio_open(struct inode *inode, struct file *file)
         if (file->f_mode & FMODE_WRITE)
                 w = 1;
 
+        kparam_block_sysfs_write(dsp);
         lock_kernel();
         ret = os_open_file(dsp, of_set_rw(OPENFLAGS(), r, w), 0);
         unlock_kernel();
+        kparam_unblock_sysfs_write(dsp);
 
         if (ret < 0) {
                 kfree(state);
@@ -258,13 +262,17 @@ static int hostmixer_open_mixdev(struct inode *inode, struct file *file)
         if (file->f_mode & FMODE_WRITE)
                 w = 1;
 
+        kparam_block_sysfs_write(mixer);
         lock_kernel();
         ret = os_open_file(mixer, of_set_rw(OPENFLAGS(), r, w), 0);
         unlock_kernel();
+        kparam_unblock_sysfs_write(mixer);
 
         if (ret < 0) {
+                kparam_block_sysfs_write(dsp);
                 printk(KERN_ERR "hostaudio_open_mixdev failed to open '%s', "
                        "err = %d\n", dsp, -ret);
+                kparam_unblock_sysfs_write(dsp);
                 kfree(state);
                 return ret;
         }
@@ -320,8 +328,10 @@ MODULE_LICENSE("GPL");
 
 static int __init hostaudio_init_module(void)
 {
+        __kernel_param_lock();
         printk(KERN_INFO "UML Audio Relay (host dsp = %s, host mixer = %s)\n",
                dsp, mixer);
+        __kernel_param_unlock();
 
         module_data.dev_audio = register_sound_dsp(&hostaudio_fops, -1);
         if (module_data.dev_audio < 0) {