[PATCH v2] staging: sm750fb: free cmap on framebuffer release

[Lucas Costa <2000.costalucas@gmail.com>]

The cmap is allocated by lynxfb_set_fbinfo() but never freed, so it is
leaked when the framebuffer is torn down.  This happens on every unbind,
and on the register_framebuffer() error path in
sm750fb_framebuffer_alloc().

Add a lynxfb_unset_fbinfo() cleanup counterpart to lynxfb_set_fbinfo()
which deallocates the cmap, and call it on teardown.  In the alloc error
path it is only called once lynxfb_set_fbinfo() has succeeded, so the
cmap is only freed when it was actually allocated.

Fixes: 81dee67e215b ("staging: sm750fb: add sm750 to staging")
Suggested-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Lucas Costa <2000.costalucas@gmail.com>
---
v2:
 - Move the cmap deallocation into a lynxfb_unset_fbinfo() cleanup
   counterpart to lynxfb_set_fbinfo(), instead of open-coding
   fb_dealloc_cmap() at each call site.
 - In the alloc error path, only unwind the cmap once
   lynxfb_set_fbinfo() has succeeded (Dan Carpenter).

 drivers/staging/sm750fb/sm750.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/sm750fb/sm750.c b/drivers/staging/sm750fb/sm750.c
index 8b93bfeb217b..68b6d4fe79ca 100644
--- a/drivers/staging/sm750fb/sm750.c
+++ b/drivers/staging/sm750fb/sm750.c
@@ -825,6 +825,11 @@ static int lynxfb_set_fbinfo(struct fb_info *info, int index)
 	return ret;
 }
 
+static void lynxfb_unset_fbinfo(struct fb_info *info)
+{
+	fb_dealloc_cmap(&info->cmap);
+}
+
 /*	chip specific g_option configuration routine */
 static void sm750fb_setup(struct sm750_dev *sm750_dev, char *src)
 {
@@ -910,6 +915,7 @@ static void sm750fb_framebuffer_release(struct sm750_dev *sm750_dev)
 	while (sm750_dev->fb_count) {
 		fb_info = sm750_dev->fbinfo[sm750_dev->fb_count - 1];
 		unregister_framebuffer(fb_info);
+		lynxfb_unset_fbinfo(fb_info);
 		framebuffer_release(fb_info);
 		sm750_dev->fb_count--;
 	}
@@ -936,12 +942,14 @@ static int sm750fb_framebuffer_alloc(struct sm750_dev *sm750_dev, int fbidx)
 
 	err = register_framebuffer(fb_info);
 	if (err < 0)
-		goto release_fb;
+		goto unset_fb;
 
 	sm750_dev->fb_count++;
 
 	return 0;
 
+unset_fb:
+	lynxfb_unset_fbinfo(fb_info);
 release_fb:
 	framebuffer_release(fb_info);
 	return err;
-- 
2.43.0