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, 125 insertions, 0 deletions

diff --git a/drivers/tty/tty.h b/drivers/tty/tty.h
new file mode 100644
index 000000000..93cf5ef1e
--- /dev/null
+++ b/drivers/tty/tty.h
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * TTY core internal functions
+ */
+
+#ifndef _TTY_INTERNAL_H
+#define _TTY_INTERNAL_H
+
+#define tty_msg(fn, tty, f, ...) \
+	fn("%s %s: " f, tty_driver_name(tty), tty_name(tty), ##__VA_ARGS__)
+
+#define tty_debug(tty, f, ...)	tty_msg(pr_debug, tty, f, ##__VA_ARGS__)
+#define tty_notice(tty, f, ...)	tty_msg(pr_notice, tty, f, ##__VA_ARGS__)
+#define tty_warn(tty, f, ...)	tty_msg(pr_warn, tty, f, ##__VA_ARGS__)
+#define tty_err(tty, f, ...)	tty_msg(pr_err, tty, f, ##__VA_ARGS__)
+
+#define tty_info_ratelimited(tty, f, ...) \
+		tty_msg(pr_info_ratelimited, tty, f, ##__VA_ARGS__)
+
+/*
+ * Lock subclasses for tty locks
+ *
+ * TTY_LOCK_NORMAL is for normal ttys and master ptys.
+ * TTY_LOCK_SLAVE is for slave ptys only.
+ *
+ * Lock subclasses are necessary for handling nested locking with pty pairs.
+ * tty locks which use nested locking:
+ *
+ * legacy_mutex - Nested tty locks are necessary for releasing pty pairs.
+ *		  The stable lock order is master pty first, then slave pty.
+ * termios_rwsem - The stable lock order is tty_buffer lock->termios_rwsem.
+ *		   Subclassing this lock enables the slave pty to hold its
+ *		   termios_rwsem when claiming the master tty_buffer lock.
+ * tty_buffer lock - slave ptys can claim nested buffer lock when handling
+ *		     signal chars. The stable lock order is slave pty, then
+ *		     master.
+ */
+enum {
+	TTY_LOCK_NORMAL = 0,
+	TTY_LOCK_SLAVE,
+};
+
+/* Values for tty->flow_change */
+enum tty_flow_change {
+	TTY_FLOW_NO_CHANGE,
+	TTY_THROTTLE_SAFE,
+	TTY_UNTHROTTLE_SAFE,
+};
+
+static inline void __tty_set_flow_change(struct tty_struct *tty,
+					 enum tty_flow_change val)
+{
+	tty->flow_change = val;
+}
+
+static inline void tty_set_flow_change(struct tty_struct *tty,
+				       enum tty_flow_change val)
+{
+	tty->flow_change = val;
+	smp_mb();
+}
+
+int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout);
+void tty_ldisc_unlock(struct tty_struct *tty);
+
+int __tty_check_change(struct tty_struct *tty, int sig);
+int tty_check_change(struct tty_struct *tty);
+void __stop_tty(struct tty_struct *tty);
+void __start_tty(struct tty_struct *tty);
+void tty_write_unlock(struct tty_struct *tty);
+int tty_write_lock(struct tty_struct *tty, bool ndelay);
+void tty_vhangup_session(struct tty_struct *tty);
+void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty);
+int tty_signal_session_leader(struct tty_struct *tty, int exit_session);
+void session_clear_tty(struct pid *session);
+void tty_buffer_free_all(struct tty_port *port);
+void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld);
+void tty_buffer_init(struct tty_port *port);
+void tty_buffer_set_lock_subclass(struct tty_port *port);
+bool tty_buffer_restart_work(struct tty_port *port);
+bool tty_buffer_cancel_work(struct tty_port *port);
+void tty_buffer_flush_work(struct tty_port *port);
+speed_t tty_termios_input_baud_rate(const struct ktermios *termios);
+void tty_ldisc_hangup(struct tty_struct *tty, bool reset);
+int tty_ldisc_reinit(struct tty_struct *tty, int disc);
+long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
+		       struct file *file, unsigned int cmd, unsigned long arg);
+void tty_default_fops(struct file_operations *fops);
+struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx);
+int tty_alloc_file(struct file *file);
+void tty_add_file(struct tty_struct *tty, struct file *file);
+void tty_free_file(struct file *file);
+int tty_release(struct inode *inode, struct file *filp);
+
+#define tty_is_writelocked(tty)  (mutex_is_locked(&tty->atomic_write_lock))
+
+int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty);
+void tty_ldisc_release(struct tty_struct *tty);
+int __must_check tty_ldisc_init(struct tty_struct *tty);
+void tty_ldisc_deinit(struct tty_struct *tty);
+
+extern int tty_ldisc_autoload;
+
+/* tty_audit.c */
+#ifdef CONFIG_AUDIT
+void tty_audit_add_data(const struct tty_struct *tty, const void *data,
+			size_t size);
+void tty_audit_tiocsti(const struct tty_struct *tty, u8 ch);
+#else
+static inline void tty_audit_add_data(const struct tty_struct *tty,
+				      const void *data, size_t size)
+{
+}
+static inline void tty_audit_tiocsti(const struct tty_struct *tty, u8 ch)
+{
+}
+#endif
+
+ssize_t redirected_tty_write(struct kiocb *, struct iov_iter *);
+
+int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
+					   const u8 *chars, size_t cnt);
+
+#endif