[PATCH 6.19 250/311] auxdisplay: line-display: fix NULL dereference in linedisp_release

Greg Kroah-Hartman
2026-04-08T19:01:57Z

From: Guangshuo Li <lgs201920130244@gmail.com>

commit 7f138de156b20d9f9da6f72f90b63c01941d97d3 upstream.

linedisp_release() currently retrieves the enclosing struct linedisp via
to_linedisp(). That lookup depends on the attachment list, but the
attachment may already have been removed before put_device() invokes the
release callback. This can happen in linedisp_unregister(), and can also
be reached from some linedisp_register() error paths.

In that case, to_linedisp() returns NULL and linedisp_release()
dereferences it while freeing the display resources.

The struct device released here is the embedded linedisp->dev used by
linedisp_register(), so retrieve the enclosing object directly with
container_of() instead.

Fixes: 66c93809487e ("auxdisplay: linedisp: encapsulate container_of usage within to_linedisp")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/auxdisplay/line-display.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/auxdisplay/line-display.c b/drivers/auxdisplay/line-display.c
index 81b4aac65807..fb6d9294140d 100644
--- a/drivers/auxdisplay/line-display.c
+++ b/drivers/auxdisplay/line-display.c
@@ -365,7 +365,7 @@ static DEFINE_IDA(linedisp_id);

static void linedisp_release(struct device *dev)
{
- struct linedisp *linedisp = to_linedisp(dev);
+ struct linedisp *linedisp = container_of(dev, struct linedisp, dev);

kfree(linedisp->map);
kfree(linedisp->message);
--
2.53.0