[PATCH 1/6] fbdev: ssd1307fb: check for fb_deferred_io_init() error

fb_deferred_io_init() allocates deferred I/O state, populating
info->fbdefio_state, or leaving it NULL if an error occurs.

Currently ssd1307fb_probe() ignores its return value.

Therefore if an error arises in fb_deferred_io_init() (for instance, due
to an allocation failure) info->fbdefio_state is left NULL.

When the file is subsequently opened, fb_open() will dereference a NULL
pointer (calling fb_deferred_io_open()).

Fix this by checking for the error.

Fixes: 56c134f7f1b5 ("fbdev: Track deferred-I/O pages in pageref struct")
Cc: <redacted>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 drivers/video/fbdev/ssd1307fb.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 4d185c754284..8fd96c37ee1a 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c

@@ -767,7 +767,11 @@ static int ssd1307fb_probe(struct i2c_client *client)
 	info->fix.smem_start = __pa(vmem);
 	info->fix.smem_len = vmem_size;
 
-	fb_deferred_io_init(info);
+	ret = fb_deferred_io_init(info);
+	if (ret) {
+		dev_err(dev, "failed to init fb deferred io: %d\n", ret);
+		goto fb_defio_error;
+	}
 
 	i2c_set_clientdata(client, info);
 

-- 
2.55.0