FAILED: patch "[PATCH] serial: 8250_mid: Fix NULL function pointer dereference on" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 7fb13fd7e9a59a37cd911efff83abe19e3ee029d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072925-designer-willow-bfb6@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7fb13fd7e9a59a37cd911efff83abe19e3ee029d Mon Sep 17 00:00:00 2001
From: Jiangshan Yi <[email protected]>
Date: Wed, 15 Jul 2026 15:35:46 +0800
Subject: [PATCH] serial: 8250_mid: Fix NULL function pointer dereference on
DNV/ICX-D/SNR platforms

Commit b1b4efea05a5 ("serial: 8250_mid: Disable DMA for selected platforms") replaced the dnv_board setup and exit callbacks with PTR_IF(false, ...), which evaluates to NULL. However, the three call sites in mid8250_probe() and mid8250_remove() unconditionally dereference these function pointers without NULL checks, causing a NULL pointer dereference (kernel oops) on any Denverton (DNV), Ice Lake Xeon D (ICX-D/CDF), or Snowridge (SNR) platform.

Fix this by adding the missing NULL checks before calling the setup and exit callbacks.

index f88809ff370b..82656645b8a6 100644
@@ -318,9 +318,11 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (!uart.port.membase)
 		return -ENOMEM;
 
-	ret = mid->board->setup(mid, &uart.port);
-	if (ret)
-		return ret;
+	if (mid->board->setup) {
+		ret = mid->board->setup(mid, &uart.port);
+		if (ret)
+			return ret;
+	}
 
 	ret = mid8250_dma_setup(mid, &uart);
 	if (ret)

@@ -336,7 +338,8 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	return 0;
 
 err:
-	mid->board->exit(mid);
+	if (mid->board->exit)
+		mid->board->exit(mid);
 	return ret;
 }
 

@@ -346,7 +349,8 @@ static void mid8250_remove(struct pci_dev *pdev)
 
 	serial8250_unregister_port(mid->line);
 
-	mid->board->exit(mid);
+	if (mid->board->exit)
+		mid->board->exit(mid);
 }
 
 static const struct mid8250_board pnw_board = {

From: Andy Shevchenko <[email protected]>

[ Upstream commit 324facd1ccb353a213ea2c2785604f2507f79297 ]

All supported platforms by this driver require ->setup() and ->exit(). Remove unneeded test for ->setup() presence.

Stable-dep-of: 7fb13fd7e9a5 ("serial: 8250_mid: Fix NULL function pointer dereference on DNV/ICX-D/SNR platforms")

---
 drivers/tty/serial/8250/8250_mid.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

index 9a4c6466ab026..c6c13ef061a0a 100644
@@ -319,11 +319,9 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (!uart.port.membase)
 		return -ENOMEM;
 
-	if (mid->board->setup) {
-		ret = mid->board->setup(mid, &uart.port);
-		if (ret)
-			return ret;
-	}
+	ret = mid->board->setup(mid, &uart.port);
+	if (ret)
+		return ret;
 
 	ret = mid8250_dma_setup(mid, &uart);
 	if (ret)

2.53.0

From: Jiangshan Yi <[email protected]>

[ Upstream commit 7fb13fd7e9a59a37cd911efff83abe19e3ee029d ]

Commit b1b4efea05a5 ("serial: 8250_mid: Disable DMA for selected platforms") replaced the dnv_board setup and exit callbacks with PTR_IF(false, ...), which evaluates to NULL. However, the three call sites in mid8250_probe() and mid8250_remove() unconditionally dereference these function pointers without NULL checks, causing a NULL pointer dereference (kernel oops) on any Denverton (DNV), Ice Lake Xeon D (ICX-D/CDF), or Snowridge (SNR) platform.

Fix this by adding the missing NULL checks before calling the setup and exit callbacks.

---
 drivers/tty/serial/8250/8250_mid.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

index c6c13ef061a0a..5f67bf4ce0fad 100644
@@ -319,9 +319,11 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (!uart.port.membase)
 		return -ENOMEM;
 
-	ret = mid->board->setup(mid, &uart.port);
-	if (ret)
-		return ret;
+	if (mid->board->setup) {
+		ret = mid->board->setup(mid, &uart.port);
+		if (ret)
+			return ret;
+	}
 
 	ret = mid8250_dma_setup(mid, &uart);
 	if (ret)

@@ -337,7 +339,8 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	return 0;
 
 err:
-	mid->board->exit(mid);
+	if (mid->board->exit)
+		mid->board->exit(mid);
 	return ret;
 }
 

@@ -347,7 +350,8 @@ static void mid8250_remove(struct pci_dev *pdev)
 
 	serial8250_unregister_port(mid->line);
 
-	mid->board->exit(mid);
+	if (mid->board->exit)
+		mid->board->exit(mid);
 }
 
 static const struct mid8250_board pnw_board = {

2.53.0