sdio: fix reference counting in sdio_remove_func()

sdio_remove_func() needs to be more careful about reference counting.  It
can be called in error paths where sdio_add_func() has never been called
e.g.  mmc_attach_sdio error path --> mmc_sdio_remove --> sdio_remove_func

Signed-off-by: Daniel Drake <dsd@laptop.org>
Reviewed-by: Matt Fleming <matt@console-pimps.org>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/mmc/core/sdio_bus.c b/drivers/mmc/core/sdio_bus.c
index d37464e296a..9e060c87e64 100644
--- a/drivers/mmc/core/sdio_bus.c
+++ b/drivers/mmc/core/sdio_bus.c
@@ -248,12 +248,15 @@ int sdio_add_func(struct sdio_func *func)
 /*
  * Unregister a SDIO function with the driver model, and
  * (eventually) free it.
+ * This function can be called through error paths where sdio_add_func() was
+ * never executed (because a failure occurred at an earlier point).
  */
 void sdio_remove_func(struct sdio_func *func)
 {
-        if (sdio_func_present(func))
-                device_del(&func->dev);
+        if (!sdio_func_present(func))
+                return;
 
+        device_del(&func->dev);
         put_device(&func->dev);
 }