mac80211: fix deadlocks in debugfs_netdev.c

The bug shows up with CONFIG_PREEMPT enabled. Pointed out by Andrew Morton.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Luis Carlos Cobo <luisca@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index 0e921aef8ecf..3e19d42e61cb 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -31,11 +31,13 @@ static ssize_t ieee80211_if_read(
         ssize_t ret = -EINVAL;
 
         read_lock(&dev_base_lock);
-        if (sdata->dev->reg_state == NETREG_REGISTERED) {
+        if (sdata->dev->reg_state == NETREG_REGISTERED)
                 ret = (*format)(sdata, buf, sizeof(buf));
-                ret = simple_read_from_buffer(userbuf, count, ppos, buf, ret);
-        }
         read_unlock(&dev_base_lock);
+
+        if (ret != -EINVAL)
+                ret = simple_read_from_buffer(userbuf, count, ppos, buf, ret);
+
         return ret;
 }
 
@@ -51,13 +53,13 @@ static ssize_t ieee80211_if_write(
 
         memset(buf, 0x00, sizeof(buf));
         buf_size = min(count, (sizeof(buf)-1));
-        read_lock(&dev_base_lock);
         if (copy_from_user(buf, userbuf, buf_size))
-                goto endwrite;
+                return count;
+        read_lock(&dev_base_lock);
         if (sdata->dev->reg_state == NETREG_REGISTERED)
                 (*format)(sdata, buf);
-endwrite:
         read_unlock(&dev_base_lock);
+
         return count;
 }
 #endif