x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 132 insertions, 0 deletions

diff --git a/drivers/net/arcnet/com20020.h b/drivers/net/arcnet/com20020.h
new file mode 100644
index 000000000..68f49fdc2
--- /dev/null
+++ b/drivers/net/arcnet/com20020.h
@@ -0,0 +1,132 @@
+/*
+ * Linux ARCnet driver - COM20020 chipset support - function declarations
+ *
+ * Written 1997 by David Woodhouse.
+ * Written 1994-1999 by Avery Pennarun.
+ * Derived from skeleton.c by Donald Becker.
+ *
+ * Special thanks to Contemporary Controls, Inc. (www.ccontrols.com)
+ *  for sponsoring the further development of this driver.
+ *
+ * **********************
+ *
+ * The original copyright of skeleton.c was as follows:
+ *
+ * skeleton.c Written 1993 by Donald Becker.
+ * Copyright 1993 United States Government as represented by the
+ * Director, National Security Agency.  This software may only be used
+ * and distributed according to the terms of the GNU General Public License as
+ * modified by SRC, incorporated herein by reference.
+ *
+ * **********************
+ *
+ * For more details, see drivers/net/arcnet.c
+ *
+ * **********************
+ */
+#ifndef __COM20020_H
+#define __COM20020_H
+#include <linux/leds.h>
+
+int com20020_check(struct net_device *dev);
+int com20020_found(struct net_device *dev, int shared);
+extern const struct net_device_ops com20020_netdev_ops;
+
+/* The number of low I/O ports used by the card. */
+#define ARCNET_TOTAL_SIZE 8
+
+#define PLX_PCI_MAX_CARDS 2
+
+struct ledoffsets {
+	int green;
+	int red;
+};
+
+struct com20020_pci_channel_map {
+	u32 bar;
+	u32 offset;
+	u32 size;               /* 0x00 - auto, e.g. length of entire bar */
+};
+
+struct com20020_pci_card_info {
+	const char *name;
+	u8 devcount;
+
+	struct com20020_pci_channel_map chan_map_tbl[PLX_PCI_MAX_CARDS];
+	struct com20020_pci_channel_map misc_map;
+
+	struct ledoffsets leds[PLX_PCI_MAX_CARDS];
+	int rotary;
+
+	unsigned int flags;
+};
+
+struct com20020_priv {
+	struct com20020_pci_card_info *ci;
+	struct list_head list_dev;
+	resource_size_t misc;
+};
+
+struct com20020_dev {
+	struct list_head list;
+	struct net_device *dev;
+
+	struct led_classdev tx_led;
+	struct led_classdev recon_led;
+
+	struct com20020_priv *pci_priv;
+	int index;
+};
+
+#define COM20020_REG_W_INTMASK	0	/* writable */
+#define COM20020_REG_R_STATUS	0	/* readable */
+#define COM20020_REG_W_COMMAND	1	/* standard arcnet commands */
+#define COM20020_REG_R_DIAGSTAT	1	/* diagnostic status */
+#define COM20020_REG_W_ADDR_HI	2	/* control for IO-mapped memory */
+#define COM20020_REG_W_ADDR_LO	3
+#define COM20020_REG_RW_MEMDATA	4	/* data port for IO-mapped memory */
+#define COM20020_REG_W_SUBADR	5	/* the extended port _XREG refers to */
+#define COM20020_REG_W_CONFIG	6	/* configuration */
+#define COM20020_REG_W_XREG	7	/* extra
+					 * (indexed by _CONFIG or _SUBADDR)
+					 */
+
+/* in the ADDR_HI register */
+#define RDDATAflag	0x80	/* next access is a read (not a write) */
+
+/* in the DIAGSTAT register */
+#define NEWNXTIDflag	0x02	/* ID to which token is passed has changed */
+
+/* in the CONFIG register */
+#define RESETcfg	0x80	/* put card in reset state */
+#define TXENcfg		0x20	/* enable TX */
+#define XTOcfg(x)	((x) << 3)	/* extended timeout */
+
+/* in SETUP register */
+#define PROMISCset	0x10	/* enable RCV_ALL */
+#define P1MODE		0x80    /* enable P1-MODE for Backplane */
+#define SLOWARB		0x01    /* enable Slow Arbitration for >=5Mbps */
+
+/* COM2002x */
+#define SUB_TENTATIVE	0	/* tentative node ID */
+#define SUB_NODE	1	/* node ID */
+#define SUB_SETUP1	2	/* various options */
+#define SUB_TEST	3	/* test/diag register */
+
+/* COM20022 only */
+#define SUB_SETUP2	4	/* sundry options */
+#define SUB_BUSCTL	5	/* bus control options */
+#define SUB_DMACOUNT	6	/* DMA count options */
+
+static inline void com20020_set_subaddress(struct arcnet_local *lp,
+					   int ioaddr, int val)
+{
+	if (val < 4) {
+		lp->config = (lp->config & ~0x03) | val;
+		outb(lp->config, ioaddr + COM20020_REG_W_CONFIG);
+	} else {
+		outb(val, ioaddr + COM20020_REG_W_SUBADR);
+	}
+}
+
+#endif /* __COM20020_H */