ieee1394: raw1394: replace BKL by local mutex, make ioctl() and mmap() thread-safe

This removes the last usage of the Big Kernel Lock from the ieee1394
stack, i.e. from raw1394's (unlocked_)ioctl and compat_ioctl.

The ioctl()s don't need to take the BKL, but they need to be serialized
per struct file *.  In particular, accesses to ->iso_state need to be
serial.  We simply use a blocking mutex for this purpose because
libraw1394 does not use O_NONBLOCK.  In practice, there is no lock
contention anyway because most if not all libraw1394 clients use a
libraw1394 handle only in a single thread.

mmap() also accesses ->iso_state.  Until now this was unprotected
against concurrent changes by ioctls.  Fix this bug while we are at it.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

2 files changed, 18 insertions, 6 deletions

diff --git a/drivers/ieee1394/raw1394-private.h b/drivers/ieee1394/raw1394-private.h
index a06aaad5b448..7a225a405987 100644
--- a/drivers/ieee1394/raw1394-private.h
+++ b/drivers/ieee1394/raw1394-private.h
@@ -22,6 +22,7 @@ enum raw1394_iso_state { RAW1394_ISO_INACTIVE = 0,
 struct file_info {
         struct list_head list;
 
+        struct mutex state_mutex;
         enum { opened, initialized, connected } state;
         unsigned int protocol_version;
 
diff --git a/drivers/ieee1394/raw1394.c b/drivers/ieee1394/raw1394.c
index 6fa9e4a21840..975ed7062aa1 100644
--- a/drivers/ieee1394/raw1394.c
+++ b/drivers/ieee1394/raw1394.c
@@ -34,6 +34,7 @@
 #include <linux/fs.h>
 #include <linux/poll.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/vmalloc.h>
@@ -2541,11 +2542,18 @@ static int raw1394_read_cycle_timer(struct file_info *fi, void __user * uaddr)
 static int raw1394_mmap(struct file *file, struct vm_area_struct *vma)
 {
         struct file_info *fi = file->private_data;
+        int ret;
+
+        mutex_lock(&fi->state_mutex);
 
         if (fi->iso_state == RAW1394_ISO_INACTIVE)
-                return -EINVAL;
+                ret = -EINVAL;
+        else
+                ret = dma_region_mmap(&fi->iso_handle->data_buf, file, vma);
+
+        mutex_unlock(&fi->state_mutex);
 
-        return dma_region_mmap(&fi->iso_handle->data_buf, file, vma);
+        return ret;
 }
 
 /* ioctl is only used for rawiso operations */
@@ -2659,10 +2667,12 @@ static long do_raw1394_ioctl(struct file *file, unsigned int cmd,
 static long raw1394_ioctl(struct file *file, unsigned int cmd,
                                                         unsigned long arg)
 {
+        struct file_info *fi = file->private_data;
         long ret;
-        lock_kernel();
+
+        mutex_lock(&fi->state_mutex);
         ret = do_raw1394_ioctl(file, cmd, arg);
-        unlock_kernel();
+        mutex_unlock(&fi->state_mutex);
         return ret;
 }
 
@@ -2724,7 +2734,7 @@ static long raw1394_compat_ioctl(struct file *file,
         void __user *argp = (void __user *)arg;
         long err;
 
-        lock_kernel();
+        mutex_lock(&fi->state_mutex);
         switch (cmd) {
         /* These requests have same format as long as 'int' has same size. */
         case RAW1394_IOC_ISO_RECV_INIT:
@@ -2757,7 +2767,7 @@ static long raw1394_compat_ioctl(struct file *file,
                 err = -EINVAL;
                 break;
         }
-        unlock_kernel();
+        mutex_unlock(&fi->state_mutex);
 
         return err;
 }
@@ -2791,6 +2801,7 @@ static int raw1394_open(struct inode *inode, struct file *file)
         fi->notification = (u8) RAW1394_NOTIFY_ON;      /* busreset notification */
 
         INIT_LIST_HEAD(&fi->list);
+        mutex_init(&fi->state_mutex);
         fi->state = opened;
         INIT_LIST_HEAD(&fi->req_pending);
         INIT_LIST_HEAD(&fi->req_complete);