devm_ioremap() returns NULL on error. Currently, mlb_usio_probe() does
not check for this case, which results in a NULL pointer dereference.

Add NULL check after devm_ioremap() to prevent this issue.

Cc: stable@vger.kernel.org
Fixes: ba44dc043004 ("serial: Add Milbeaut serial control")
Signed-off-by: Henry Martin <bsdhenrymartin@gmail.com>
---
V1 -> V2: Add cc: stable line.

 drivers/tty/serial/milbeaut_usio.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/milbeaut_usio.c b/drivers/tty/serial/milbeaut_usio.c
index 059bea18dbab..4e47dca2c4ed 100644
--- a/drivers/tty/serial/milbeaut_usio.c
+++ b/drivers/tty/serial/milbeaut_usio.c
@@ -523,7 +523,10 @@ static int mlb_usio_probe(struct platform_device *pdev)
 	}
 	port->membase = devm_ioremap(&pdev->dev, res->start,
 				resource_size(res));
-
+	if (!port->membase) {
+		ret = -ENOMEM;
+		goto failed;
+	}
 	ret = platform_get_irq_byname(pdev, "rx");
 	mlb_usio_irq[index][RX] = ret;
 
-- 
2.34.1

…
> Add NULL check after devm_ioremap() to prevent this issue.

Can a summary phrase like “Prevent null pointer dereference in mlb_usio_probe()”
be a bit nicer?

Regards,
Markus

On Thu, Apr 03, 2025 at 10:50:36AM +0200, Markus Elfring wrote:
> …
> > Add NULL check after devm_ioremap() to prevent this issue.
> 
> Can a summary phrase like “Prevent null pointer dereference in mlb_usio_probe()”
> be a bit nicer?
> 
> Regards,
> Markus
> 

Hi,

This is the semi-friendly patch-bot of Greg Kroah-Hartman.

Markus, you seem to have sent a nonsensical or otherwise pointless
review comment to a patch submission on a Linux kernel developer mailing
list.  I strongly suggest that you not do this anymore.  Please do not
bother developers who are actively working to produce patches and
features with comments that, in the end, are a waste of time.

Patch submitter, please ignore Markus's suggestion; you do not need to
follow it at all.  The person/bot/AI that sent it is being ignored by
almost all Linux kernel maintainers for having a persistent pattern of
behavior of producing distracting and pointless commentary, and
inability to adapt to feedback.  Please feel free to also ignore emails
from them.

thanks,

greg k-h's patch email bot